Biological flora of New Zealand 10.Phormium tenax, harakeke, New Zealand flax

Priscilla M. Wehi; Bruce D. Clarkson

We review the biosystematics, chemistry, phenology, ecology, and cultural and economic uses of Phormium tenax, a widespread iconic New Zealand monocotyledon. Phormium tenax is endemic to New Zealand, Norfolk Island, and the Chatham Islands, and is distinguished from the sole other member of the genus, P. cookianum, by its erect trigonous seed capsules and red flowers, despite incomplete barriers to hybridisation. Flowers produce abundant nectar and are bird pollinated. Seed is orthodox and tolerates drying, while chilling overcomes dormancy. Rich, well-drained alluvial and organic soils encourage abundant growth in P. tenax but prolonged flooding and drought reduce growth and survival. Lack of tolerance to both frost and low mean annual temperatures distinguish its environmental niche from that of P. cookianum, but further research is required to characterise these differences more accurately. Phormium tenax is a significant component of vegetation on coastal cliffs, slopes, and dunelands; in estuarine shrublands; and lake margin and freshwater communities. Wide morphological variation in Phormium has led to cultivar development by Maori for weaving and by horticulturalists for ornamental garden use. Phormium tenax is important in many ecological communities as a food source, and is often used in restoration and revegetation plantings.

Wehi & Clarkson—Biological lora of NZ: tenax New Zealand Journal of Botany, 2007, Vol. Phormium 45: 521–544 0028–825X/07/4504–0521 © The Royal Society of New Zealand 2007 521 Biological lora of New Zealand 10. Phormium tenax, harakeke, New Zealand lax Priscilla M. Wehi BRuCe D. ClaRkSoN Department of Biological Sciences university of Waikato Private Bag 3105 Hamilton 3240, New Zealand pwehi@waikato.ac.nz Abstract We review the biosystematics, chemistry, phenology, ecology, and cultural and economic uses of Phormium tenax, a widespread iconic New Zealand monocotyledon. Phormium tenax is endemic to New Zealand, Norfolk Island, and the Chatham Islands, and is distinguished from the sole other member of the genus, P. cookianum, by its erect trigonous seed capsules and red lowers, despite incomplete barriers to hybridisation. Flowers produce abundant nectar and are bird pollinated. Seed is orthodox and tolerates drying, while chilling overcomes dormancy. Rich, well-drained alluvial and organic soils encourage abundant growth in P. tenax but prolonged looding and drought reduce growth and survival. lack of tolerance to both frost and low mean annual temperatures distinguish its environmental niche from that of P. cookianum, but further research is required to characterise these differences more accurately. Phormium tenax is a signiicant component of vegetation on coastal cliffs, slopes, and dunelands; in estuarine shrublands; and lake margin and freshwater communities. Wide morphological variation in Phormium has led to cultivar development by Maori for weaving and by horticulturalists for ornamental garden use. Phormium tenax is important in many ecological communities as a food source, and is often used in restoration and revegetation plantings. Keywords biological lora; ibre; lax; freshwater wetlands; harakeke; Hemerocallidaceae; Maori; New Zealand; Phormium; weaving B07002; Online publication date 30 October 2007 Received 21 February 2007; accepted 13 August 2007 INTRODUCTION Phormium tenax (J.R. & G.Forst.) is a familiar plant to most New Zealanders, and can be seen along roadsides, in gardens, and in swamps. Commonly known as New Zealand lax or harakeke (as well as korari in northern New Zealand), it is one of the two species of the genus Phormium (the other is P. cookianum). P. tenax is valued highly by Maori and european colonists. Traditional Maori use of P. tenax prior to european colonisation was extensive, with items such as clothing, nets, baskets, and mats plaited from the leaf strips or woven from ibre (muka) stripped from the leaves (Buck 1911, 1923, 1926). Trade in P. tenax ibre burgeoned from irst european contact with Maori in the late 18th century, with scientiic research in this period and throughout the following century closely related to its economic use (Cross 1912). This early research focused on techniques to improve commercial harvesting and processing (i.e., mechanical stripping), but also contains information on traditional Maori cultivars, ecology, and leaf structure. a resurgence in Maori weaving in the second half of the 20th century has revived the search for traditional knowledge of the uses and management of Phormium cultivars. Recognition of its importance to Maori as a ibre plant has led to further investigations of its cultivation, processing, ibre properties, and genetic variation within the species. an emerging feature is the collaborative research between scientists and Maori weavers into areas of common interest (e.g., Harris & Woodcock-Sharp 2000; McBreen et al. 2003; More et al. 2003; Harris et al. 2005, 2007). Moreover, despite the collapse of the Phormium lax milling industry in the early 20th century, there is renewed interest in the potential of P. tenax for future commercial development. Phormium tenax is increasingly used in ecological restoration plantings, erosion control, farm hedging, and riparian strips (e.g., Reay & Norton 1999; McGruddy 2006), and as a decorative garden plant (Heenan 1991; McGruddy 2006). Given this increasing cultural, economic, and ecological interest, we consider a review of published biological material warranted, 522 to encourage further research and development of the species. The taxonomy, morphology, distribution, habitats and plant communities, and other biological associations of P. tenax are considered here, along with its current and historic uses as a traditional ibre plant. Nomenclature follows allan (1961), Connor & edgar (1987), Moore & edgar (1970), and Webb et al. (1988) unless otherwise stated. Whilst all material that refers to P. tenax in passing has not been included, each section draws from the principal publications. Information about commercial harvesting and ibre production is not included. MORPHOLOGICAL DESCRIPTION Phormium tenax is a monocotyledonous tussockherb (Moore & edgar 1970; Johnson & Brooke 1989). It is a tall, tufted, herbaceous perennial that increases by budding from a stout rhizome. The leaves are most usually green (although they can be pigmented or variegated), distichous and sword-like, and grow up to 3 m long in fan-like tufts that form robust clumps. leaves are strongly keeled, folded, and can be 50–120 mm wide. They are marked by long, ine close striations and strengthened by bast ibres. The leaf butt is stiff and heavy. Dead leaves fall to the base of the plant, especially around its perimeter. Flower stalks (peduncles) are tall and distinctive, growing up to 5 m tall, and lowering in summer from around November to February. an inlorescence consists of one main stem with between 8 and 15 alternating secondary peduncles. Peduncles are usually 20–30 mm in diameter, dark, and glabrous. Peduncles produce up to seven tertiary branches, with between one and four clusters of lowers attached. each cluster has between one and ive lowers (Becerra & lloyd 1992). Flowers are 25–50 mm long (cf. 10–80 mm long according to Wardle (1991)) and erect with leshy tepals which are coloured various shades of deep red. They lie on short branches alternately on opposite sides of the main axis, lying on one plane (atkinson 1921a). The tips of the tepals are slightly recurved. Flowers are bisexual and protandrous (that is, the pollen is mature before the stigma is receptive). The six stamens are taller than the tepals, and are inserted at the base of the perianth. The ilaments are long and glabrous, and are inserted in a pit at the back of the anther. These ilaments are long enough to carry the anthers beyond the mouth of a lower. anthers are New Zealand Journal of Botany, 2007, Vol. 45 linear-oblong. a large quantity of waxy, orange-coloured pollen is produced. Pollen grains are trichotomocolpate, tetrahedral, oblate, and medium sized with a diameter of c. 36 µm (Cranwell 1953; Puri 1960). The grains are triradiate and, thus, furrowed (Cranwell 1953) and the pollen is light and powdery. The six members of the perianth (which consists of the calyx and corolla) form a curved tube 25–50 mm long. The ovary (with many ovules) is inside the ring of stamens. The ovary is erect, superior, sessile, and elongate. Carpels are straight. Seed capsules are usually less than 100 mm long, trigonous, and not twisted (erect). The seed capsules remain irm and dark with age. Seeds are lattened, almost winged, black and shining, and 9–10 × 4–5 mm in size. Morphological differences have been described from different geographical localities. Phormium tenax from the Three kings, Poor knights, Mokohinau, and Hen and Chickens Islands north of auckland (Fig. 1) features decurved leaves with a goldenyellow laminal margin (de lange & Cameron 1999). a much smaller habit, loppy decurved leaves, and smaller lowers, fruits, and seeds have been reported for the Chatham Islands form (Crisp et al. 2000), as have broader leaves (Greenwood 1992). Phormium tenax and P. cookianum can be distinguished by their lowers, fruits, and other features (Wardle 1979), although differences are less clear cut in zones of high hybridisation (Smissen & Heenan 2007). However, the erect seed capsules provide one of the most useful distinguishing characters of P. tenax, contrasting with the twisted, pendulous seed capsules of P. cookianum. ANATOMY Studies of leaf anatomy have shown that P. tenax has a leaf structure typical of monocotyledons. Bundles of sclerenchyma ibres lie parallel to the keel of the leaf but overlap each other in a spiral manner. These sclerenchyma ibres are composed of elongated hollow cells known as ultimate ibres (Hutton 1869; Nottidge 1869; Cross 1912). as Carr et al. (2005) have noted, microscopic studies of the sclerenchyma cells have not reached a consensus on the shape, length, and adhesion of the ultimate ibres (diameter 5–20 µm, length 3–60 mm) (Hutton 1869; Nottidge 1869; McNab 1872; Cross 1912; atkinson 1922; king & Vincent 1996). The sclerenchyma ibres are bonded together by hemicelluloses and lignin: extraction of the ibres involves the removal of the leaf epidermis, and the bonds dissolve in either boiling Wehi & Clarkson—Biological lora of NZ: Phormium tenax 523 Fig. 1 New Zealand, showing places mentioned in the text. water or alkali solutions (Hutton 1870). Reports of the percentage of cellulose and lignin also differ markedly. These inconsistencies may partly arise through differences in the Phormium cultivars examined, as this is often not speciied, especially in older research. Nuclear magnetic resonance spectroscopy work has indicated lower guaiacyl lignin content (which may enhance photodegradation) in ibre from the upper layer of leaf blades (Newman et al. 2005). This inding was used to support the opinion that Maori preferentially extracted ibre from the upper blade layer because those ibres were less likely to photodegrade. For 15 cultivars grown at the same site, the lowest contents of guaiacyl were in varieties traditionally used for ibre (muka) extraction, and the highest in those used to provide blade strips for plaiting (Newman et al. 2005) although it is possible that the difference between cultivars may be an artefact of stripping technique. In another study there were no signiicant differences of cellulose content of three traditional cultivars (Makaweroa, arawa, and Tapamangu), although Makaweroa ibre strands (muka) and ultimate ibres were longer. Makaweroa also had a lower extension at maximum load and maximum extension (Carr et al. 2005). Recent research has examined the properties of ibre in cultivars that are highly valued by Maori for the ease by which they can be stripped and the qualities of the extracted ibre (Harris & WoodcockSharp 2000; Carr et al. 2005). This includes analysis 524 of structural stiffness of leaves (king et al. 1996), fracture and mechanical properties (king & Vincent 1996; Harris & Woodcock-Sharp 2000; Jackman 2000), and the effects of ibre extraction on leaf anatomy (king 2003). Wetland monocots often have massive rhizomes that ramify below the surface of the soil or submerged mud (Wardle 1991). Phormium tenax has an adventitious root system with stout leshy roots that can extend either vertically or laterally (atkinson 1922; Poole 1940). The root structure changes as the roots extend downwards, so that the many root hairs present near the surface of the soil are absent from the deep root system. Instead the root is furnished with a thin outer epidermis “skin” near the root apex which readily allows the water to pass through it (Cockayne 1919a; atkinson 1922). CYTOLOGY The chromosome number of P. tenax is 2n = 32 (Moore & edgar 1970; Dawson 2000). Hair & Beuzenberg (1966) reported 2n = 32 in both P. tenax and P. cookianum. de lange & Murray (2002) found 2n = 32 for Phormium aff. tenax from the Three kings Islands and Chatham Islands. TAXONOMY AND RELATIONSHIPS There has been debate over the taxonomic classiication of Phormium since the mid 1800s (Henderson & Clifford 1984), with treatments differing in both the families to which it is assigned and the relatives with which it is grouped. Hutchinson (1934) included it in the agavaceae, as did Moore & edgar (1970). However, Phormium is separated from other members of the agavaceae by chromosome number and the morphology of the equidistant distichous leaves (cf. spirally inserted leaves), as well as microspore, pollen grain structure, and cellular differences such as having trichotomosulcate rather than simple monosulcate germ pores and simultaneous rather than successive divisions of their pollen mother cells (Cave 1962). as well, many of the agavaceae are arborescent, while Phormium is not. Thus, the supericial similarities between Phormium and other members of this group result from convergent evolution not shared ancestry. Placement in the liliaceae because of the lilylike lowers has also been widely rejected, although New Zealand Journal of Botany, 2007, Vol. 45 Dianella, which is frequently considered to have features in common with Phormium, is still categorised as part of the liliaceae by some authors (Henderson & Clifford 1984). Both are rhizatomous perennials, and have leaves that are characteristically fused between sheath and blade and lowers that are morphologically similar. Pollen shape and seed proteins are also similar. as well, both Phormium and Dianella have been ibre sources, indicating a similar vascular leaf structure (Henderson & Clifford 1984). Phormium may be regarded as part of the Phormiaceae (Connor & edgar 1987)*. The Phormiaceae was proposed by agardh (1858) for Phormium and Blandfordia, although Blandfordia is now generally resolved by modern researchers as belonging within the liliaceae (Henderson & Clifford 1984). Henderson & Clifford (1984) recircumscribed the family Phormiaceae to include only Dianella, Rhuacophila, Stypandra, and Excremis besides Phormium, excluding Xeronema, although Xeronema was later put forward as another possible inclusion (Connor & edgar 1987). This small, mainly southern hemisphere family has around seven genera and 30 species currently recognised, including the genera Dianella, Stypandra, Thelionema, Excremis, Agrostocrinum, and Xeronema with members in New Zealand, australia, Nepal, and Zimbabwe (Watson & Dallwitz 1992 onwards). Conran’s (1987) comparison of phenetic analyses (involving 94 characters) demonstrated afinities between the Phormiaceae and the Geitonoplesiaceae, which share the distinctive features of porate anthers and trichotomosulcate pollen. The Phormiaceae also share convergent perianth venation and convergent leaf venation with the Geitonoplesiaceae and Herreriaceae. These characters are also present in some anthericaceae, and Conran (1987) suggested that further investigation is needed to establish the relationships of the Phormiaceae with the remainder of the black-seeded asparagales. The liliales superfamily has now been redeined on molecular and morphological evidence to exclude the asparagales, to which both the agavaceae and Phormiaceae belong (Watson & Dallwitz 1992 onwards). The liliales and asparagales appear to have evolved many traits in parallel, but two of the most important characters separating them are the presence of septal nectaries in the ovary and *Subclass Monocotyledonae. Suborder liliilorae; order asparagales. Family Phormiaceae. Wehi & Clarkson—Biological lora of NZ: Phormium tenax phytomelan in the seed coat of the asparagales (Meerow 2002). However, the classiication of Phormium has not yet been completely resolved. although Dahlgren et al. (1985) had previously placed the day lily Hemerocallis in a monogeneric Hemerocallidaceae in the asparagales, more recent authors have expanded the Hemerocallidaceae to include Phormium and other related species from the Phormiaceae, based on recent molecular rbcl studies (Chase et al. 1996). Serological investigations of Phormium have also shown strong afinities with Dianella and Hemerocallis (Conran 1987). as Hemerocallidaceae is the older name with priority, this is used in preference to Phormiaceae. accordingly, the Hemerocallidaceae currently has around 18 genera, including Dianella, Stypandra, Excremis, Agrostocrinum, Rhuacophila, and Thelionema as well as Hemerocallis (chase et al. 1996; Zomlefer 1999). Further evaluation of these genera and their taxonomy is needed as, for example, chemotaxonomic studies have identiied an unusual neurotoxin that has been isolated from Hemerocallis, Dianella, and Stypandra, and enquiry into other related genera may be merited (Zomlefer 1999). The ancestral species of Phormium, Luminidites phormioides, has appeared in south-eastern australia and New Zealand in the fossil record of the late eocene in the Tertiary period of the Cenozoic era (Wardle 1991; Macphail 1997), offering evidence of an ancient lineage that has since been extirpated in australia. long-distance dispersal has been strongly implicated in establishing trans-Tasman distributions between australia and New Zealand (e.g., Winkworth et al. 1999) and it is possible that this occurred in the Phormium lineage. it also seems most likely that the spread of Phormium to Norfolk Island occurred via long-distance dispersal after the break-up of Gondwanaland, as is the case with a number of other species (Pole 1994), although this dispersal method has recently been questioned by others (Macphail et al. 2001). They instead suggested Polynesian introduction of the species as an explanation for its absence in the fossil record there (in particular, to explain its absence in a core taken near abundant extant P. tenax) (Macphail et al. 2001). Recent Quaternary diversiication of the genus, based on genetic ITS results for several P. tenax cultivars and P. cookianum, has been suggested (McBreen et al. 2003). Further evidence for the evolution of the genus is provided by the incomplete sterility barrier and hybridisation when they are found together (Cross 1915; Cockayne 1923), although the species are generally found in distinct 525 environments. Hybrids have been produced from controlled crosses (allan & Zotov 1937) and recent molecular evidence conirms wild hybrids (Smissen & Heenan 2007). There is evidence that some traditional Maori cultivars are hybrids of the species, including Paoa, aohanga, and Mawaru (Newman et al. 2005). Work on the extent and origin of variation within Phormium is incomplete. Phormium tenax was irst described and then introduced to europe by labillardière in the late 18th century (labillardière 1803) and is now established in many other parts of the world, including australia, europe, Ireland, and the uSa. Phormium tenax is now recognised as an invasive plant in some parts of the world following its introduction as an economic crop, for example, in St Helena and Tristan da Cunha islands in the South atlantic and in Hawai’i (Harris 2002). INTRASPECIFIC AND INTERSPECIFIC VARIATION Phormium has signiicant morphological and genetic variability. Cross (1912) identiied 32 cultivars of P. tenax based on habit, leaves, inlorescences, lowers, and capsules, while Maori traditionally classiied at least 60 cultivars of P. tenax for weaving based primarily on the strength and quality of ibre (Cross 1912; Heenan 1991). Horticulturalists have developed a commercial range of cultivars for garden use, mostly distinguished by variation of leaf colour and variegation. Heenan’s (1991) checklist usefully outlined known cultivars at that time, including varieties used and developed by both Maori and horticulturalists. Traditional Maori weaving cultivars collected by Rene orchiston from sites around the country (but primarily the eastern North Island) are represented in a living collection maintained by landcare Research at lincoln and Havelock North. Descriptions and origins of these cultivars recorded by orchiston have been compiled by Scheele (2005). Genetic studies of traditional Maori cultivars and putative hybrids in the wild are currently under way (R. Smissen pers. comm.), and may clarify the provenance of some traditional cultivars. Because of the extreme variability of both species of Phormium, taxonomic distinctions between some variants are believed possible (Wardle 1979; de lange & Cameron 1999). Maori weavers have noted that the same cultivars grow differently in differing conditions (Wehi 2006). Certainly, wild P. tenax shows an array of morphological forms which appear to be related to 526 New Zealand Journal of Botany, 2007, Vol. 45 habitat features such as soil fertility. To investigate the contributions of genetic and phenotypic variability, 12 Maori cultivars were chosen for a replicated growth experiment using clones at 11 different sites from kaitaia to otago (Harris et al. 2005). The sites were chosen to cover a wide range of conditions relating to climate, latitude, soil fertility, and water availability, and clones of each cultivar were planted at each site. Measurements of variables such as mean leaf length, blade width, plant circumference, cold damage, and shoot number were taken over several years and examined in relation to seasonal effects, days from planting, and site. Climatic, edaphic, and biotic factors acted simultaneously to inluence plant performance at each site. Together these factors brought about marked differences of leaf length growth between sites and cultivars responded differently to them. For example, leaf length of the cultivars kohunga, Maeneene, and Ngaro increased rapidly compared with the cultivars ate and oue. Cultivars differed signiicantly in their rate of new shoot formation (which was also inluenced by site) so that Maeneene, for example, had a high rate of new shoot production. Cold damage also varied between cultivars, and sites. Mclean (2003) found signiicant variation among maternal families of P. tenax for germination and establishment characteristics, indicating heritable variation for some traits and local adaptation to microsites. That study was carried out using seed families selected from ive New Zealand populations germinated in three substrate types and two moisture regimes. Mclean’s (2003) study showed that the availability of water and substrate characteristics had effects on seedling emergence, size (mass and height), and survival. Germination and seedling survival were greatest in a sand substrate, but seedlings were smaller than those grown in other substrates. This indicates optimum microsite requirements may vary at different life cycle stages. Within P. tenax several variants have been suggested, some of which may warrant speciic status, for example, P. aff. tenax of Norfolk Island, Chatham Islands, and Three kings Islands. Here we treat P. tenax as a single species, i.e., as P. tenax sens. lat. Hexacosanol, 7-hydroxy-5-methoxy-6-methylphthalide, and 4-methoxycarbonyl-beta-orcinol are found only in P. tenax roots. Cucurbitacin D, cucurbitacin I, and farrerol occur in the leaves (Cambie 1996). Viscosity of the exudate from the leaf base is due to an acidic xylan polysaccharide, comprising a chain of linked xylosyl residues and side chains including xylosyl and glucuronic acid residues (Tauwhare et al. 2006). arabinosyl residues are also found in the exudate. The polysaccharides are very highly branched, placing the Phormium polysaccharides in a group with brea, sapote, and yabo gums (Sims & Newman 2006). The chemistry of the exudate differs considerably between cultivars, and it is possible that xylosyl in exudate could be a chemotaxonomic marker for distinguishing taxa within Phormium (Tauwhare et al. 2006). Xylose contents have been reported for all cultivars in the Rene orchiston Collection, with higher values for P. tenax (including cultivars such as Makaweroa, arawa, and Taeore) than in P. cookianum. The structural heterogeneity of fructans within excised leaves has been suggested as a chemotaxonomic aid within the order asparagales (Sims et al. 2001). Deterioration of black-dyed ibres in articles woven by Maori has instigated research on the chemical properties of Phormium leaves, and the pH and iron content of the black dye. Phormium leaves are cellulosic, with high hemi-cellulose content (Daniels 1999). To create a traditionally woven black article made from P. tenax, the article is irst immersed in a mordant and then placed in mud (an iron/plant polyphenol complex) (Daniels 1996). However, with time, the ibre becomes brittle and weak (Twose 1988; Daniels 1999). The hemi-cellulose content of the ibre (of which the main constituent sugar is xylan) results in an intrinsically more reactive ibre than if cellulose were the main component; xylosidic bonds are more easily hydrolysed than those of cellulose and, thus, more accessible to other chemicals and susceptible to degradation (Daniels 1999). as well, the negative effects of acid and iron on polysaccharides, including cellulose, act to degrade the Phormium ibres. CHEMISTRY REPRODUCTIVE BIOLOGY Cambie (1996) published a list of known phytochemical constituents in P. tenax. chrysophanol, musizin, stypandrone, and beta-sitosterol are found in the roots of both P. cookianum and P. tenax. Flowering Mast seeding for P. tenax has been reported (Webb & kelly 1993). However, overall control of lowering has not yet been determined. Phormium tenax Wehi & Clarkson—Biological lora of NZ: Phormium tenax lowers irregularly, and Brockie (1986) concluded from a 10 year study of lowering performance that intensity luctuates annually. He believed that the data supported a quasi-triennial cycle triggered by high air temperatures the previous late summer or autumn, as suggested by Connor (1966). Brockie (1986) suggested that summed april to June maximum air temperatures in excess of 54°C were required to stimulate heavy lowering, as correlations with environmental variables explained the data better than geographical synchrony or cyclic depletion of resources. Craig & Stewart (1988) also noted the seasonal development of inlorescences, and the relationship to mean temperature of the previous april, May, and June. This effect was not observed for P. tenax in a more recent study based on an 18 year time series, although the study provided strong evidence that high temperatures in the prior summer or autumn act as a trigger for mast lowering in many New Zealand genera (Schauber et al. 2002). It is possible that P. tenax masting may respond to more subtle temperature cues that were not identiied in the analysis. Flowering time in many species becomes more concentrated with increasing latitude and altitude, and peaks in late spring rather than the early spring of the northern lowlands (Godley 1979; Wardle 1991; Harris et al. 2006). on Rangatira Island, Chatham Islands, the length of the lax lowering period varied at different sites on the island, with exposed summit sites having a shorter and later lowering period, and more sheltered sites having an earlier and longer lowering period (Dilks et al. 1998). In some american experiments, lower opening appeared to be related to temperature, relative humidity, and diurnal periodicity (Puri 1960). Craig & Stewart (1988) observed that lowers are hermaphroditic and protandrous and sexual reproduction is by large inlorescences. During the female phase, the style curves forward and the stamens remain behind it (Becerra & lloyd 1992). Becerra & lloyd (1992) reported that lowers on peduncles located in the middle and bottom of an inlorescence generally open irst, and the uppermost lowers open last. as well, terminal lowers in the tertiaries and clusters open irst. Puri (1960) found that pollen matured in layers, and his initial data indicated that the rate of dehiscence of anthers appeared to be related to environmental conditions such as temperature and relative humidity. Puri (1960) also investigated characteristics of pollen storage with regard to possibilities of crossing early and late cultivars of P. tenax. Pollen longevity in storage depended on low humidity and low temperature: pollen collected 527 6 hours after the beginning of anther excision could be stored for 181 days with germination success of 45%. However, pollen collected at later stages of maturity germinated much less successfully. Premature lower fall occurs in this species, as in many other monocotyledons. This strategy appears primarily related to strong internal competition for resources with crossed fruits on the same plant (Becerra & lloyd 1992; Jesson et al. 2006). ethylene does not appear to regulate the abscission of plant parts in P. tenax (van Doorn 2002). Flowers produce abundant nectar with high standing crops. Honeyeaters such as tui (Prosthemadera novaeseelandiae) and bellbirds (Anthornis melanura) feed heavily on nectar before and during breeding (Stewart & Craig 1985) but high annual variability in lowering makes nectar an unreliable food source (Craig & Stewart 1988). over four years at Tiritiri-Matangi Island in the Hauraki Gulf, volumes per lower varied from 135.1 ± 6 to 166 ± 11.9 µl, and concentrations from 15.8 ± 0.2 to 20.3 ± 0.6 % w/w (Craig & Stewart 1988), with male phase lowers producing signiicantly higher volume and concentration of nectar. Newly opened, pollenladen lowers at four Wellington sites provided less nectar, with a mean of between 32 and 65 µl per lower (Brockie 1996). Thomson (1927) reported that lowers were often ruptured by birds such as bellbirds and tui. Pollination and seeding Phormium tenax is primarily bird pollinated (Cockayne 1919a; Craig & Stewart 1988), although wind, water, bees and other insects have also been suggested as agents (Cross 1912; atkinson 1921a; Thomson 1927; Puri 1960). Thomson (1927) observed tui, bellbirds, stitchbirds (Notiomystis cincta), kaka (Nestor meridionalis), kakariki (Cyanoramphus spp.), and white-eyes (Zosterops lateralis novae-seelandiae) collecting nectar, and noted that their feathers picked up pollen and carried it from lower to lower. Craig (1989a) examined the different contributions of resident and non-resident tui to pollination on Tiritiri-Matangi Island. Resident tui started and ended a foraging bout within the local area and advertised their presence by singing. They moved more frequently between the inlorescences of several plants than non-resident tui, who lew into the area from a distance, infrequently moved between the inlorescences of different plants, and overall were estimated to be responsible for only 15% of all viable seeds produced despite making similar 528 numbers of foraging visits to P. tenax plants (craig 1989a). Non-native birds seen to feed on Phormium nectar and believed to be pollinators are starlings (Sturnus vulgaris) and blackbirds (Turdus merula) (Sparrow 1965). Seven sources have reported the use of Phormium by honeybees (Apis mellifera) (Cockayne 1919b; Butz Huryn 1995). Puri (1960) described P. tenax as entomophilous, as bees appear to be attracted to orange but not the less mature yellow pollen. Phormium tenax naturally outcrosses (Cross 1912; Jesson et al. 2006), and the pollen in any individual lower is ripe before the stigma of the same lower is ready to receive it so that self pollination is reduced (Puri 1960). after fertilisation the ovules develop into seeds. Seed capsules open explosively, and water dispersal is the likely mechanism of seed dispersal (Jesson et al. 2006) although the seed is light and can be blown some distance. The seed loats, and can germinate while still loating (W. Harris pers. comm.). Hampton & Hill (2002) reported the dry weight of a P. tenax seed as 0.005 g. Phormium tenax has an orthodox seed that tolerates drying, remaining viable when desiccated to a moisture content of <20% (Mackay et al. 2002). Seed germination data are somewhat conlicting; one author reported that alternating low and high temperatures were required for high seed germination (Puri 1960), but other researchers have shown that chilling overcomes dormancy in most P. tenax seeds (Metcalf 1995; Mackay et al. 2002). Metcalf (1995) reported that seed stored in cool moist conditions for 5 months germinated within 12 days. Stratiication for 8–10 weeks has broken dormancy, and 12 weeks stratiication has resulted in 95% germination (Mackay et al. 2002). Thus, seed should optimally be stored with low seed moisture content at 5°C (Mackay et al. 2002). Craig & Stewart (1988) proposed that outcrossed seeds are preferentially retained by P. tenax plants. Craig (1989b) examined the differences in seeds between self-pollinating and cross-pollinating P. tenax plants. He detected differences between pollination of lowers from the same and different inlorescences on the same plant and concluded that the plant recognises different levels of self. although sample sizes were small, there were clear relationships between seed size, viability, and pollination source. Craig (1989b) further proposed that maternal nutrition in P. tenax plants may set the overall limit of annual investment in seed. He found that outcrossing lowers produced mainly large seeds with the greatest amount of endosperm. These lowers would also promote the greatest genetic diversity. Craig (1989a) New Zealand Journal of Botany, 2007, Vol. 45 concluded that P. tenax receives a greater proportion of self-pollen on its stigmas, but sets seed from only 20% of these. although these experiments showed P. tenax to be generally self-incompatible, the results were not repeated in later experiments of self and cross-pollination on separate inlorescences (Becerra & lloyd 1992). Nonetheless, selfed lowers had a signiicantly reduced ability to set fruit with mixed pollination, supporting a hypothesis of self-incompatibility. Further, the strength of incompatibility increased with proximity of the pairs of selfed and crossed lowers on an inlorescence (Becerra & lloyd 1992). Becerra & lloyd (1992) cautioned that these results indicate that the success of self-pollinated fruits can be overestimated in natural conditions. They also considered that competition between lowers for retention depends on the proximity of lowers to each other, describing the abscission of selfed lowers as competition dependent with the mechanism operating at the level of the whole lower. They suggested that the preferential abortion of selfed lowers may be an expression of self-incompatibility acting before fertilisation or, alternatively, caused by the abortion of selfed seeds after fertilisation. later experimental work by Jesson et al. (2006) found signiicantly less germination of selfed seeds than open pollinated seeds. They detected increased fruit set on peduncles in plants that also had bagged secondary peduncles elsewhere on the inlorescence (allowing only selfed fruit set on the bagged peduncles), suggesting that resources can be reallocated between peduncles to provision better quality offspring. Vegetative reproduction Phormium propagates vegetatively by the production of ramets (also known as offshoots or fans) from underground rhizomes, so that plants consist of varying numbers, up to several hundred, of fans of the same genetic stock. Poole (1940) reported bushes with up to 300 ramets. Ramet formation for plants raised from seed is slow, with estimations of up to 15 ramets after 3 years (Poole 1940). Harris et al. (2005) found that ramet number varied signiicantly with cultivar type: Maeneene, for example, produced ramets at a faster rate, with around 134 ramets likely after 3 years. Ramets mature in 3–6 years to produce inlorescences and then senesce after lowering (Poole 1940). eight to ten leaves are usually produced per ramet (Poole 1940). leaf growth is reduced at cooler sites, especially where drought, low soil fertility, and weed competition occur, and expansion of basal circumference also varied with Wehi & Clarkson—Biological lora of NZ: Phormium tenax cool seasons (Harris et al. 2005). The high relative growth rate, tall stature, consolidated growth form, vigorous lateral spread, and rhizatomous habit of P. tenax indicate it is a competitor according to Grimes’ dimensions of plant life history (Crawley 1997). 529 Geographic range Phormium tenax is endemic to New Zealand, Norfolk Island, and the Chatham Islands (Miller 1930; Critchield 1951; Johnson & Brooke 1989), although Polynesian introduction to Norfolk Island has been suggested (Macphail et al. 2001). It was most likely introduced by Maori and/or early european whalers to Raoul Island in the kermadec Islands, and to Campbell Island and auckland Islands in the subantarctic (Critchield 1951; Johnson & Brooke 1989). one of the earliest distribution overviews was provided by Sparrow (1965), who reported the presence of P. tenax in the North Island in Wellington, Northland, and South auckland especially, with small areas in Taranaki, Hawke’s Bay, and the east Coast in 1962–3. In the South Island, Sparrow (1965) identiied Marlborough, Canterbury, Westland, and Southland as areas of high abundance, although much of this pattern was attributed to the draining of Typha orientalis swamps with consequent lowering of the water table. Phormium tenax is widespread throughout the country. It has been recorded from northern offshore islands, such as the Three kings Islands, through open areas of the North Island, and as far south as Stewart Island, albeit frequently in stunted form (Wilson 1987). (Bidwill 1952) recorded P. tenax specimens at least 4 m tall covering many miles on the plains near Matamata in the Waikato, being found in all the moist places which were not actually bog. Critchield (1951) identiied an annual rainfall range for P. tenax of 508–3810 mm. More recent data based on the environmental analysis of point data provide evidence of presence in areas of higher rainfall (>4330 mm), although it does not appear to be present in areas of extreme rainfall (Wehi 2006). Drought kills the root hairs that absorb water near the surface, impairing water absorption (atkinson 1922). Drought stress may be critical when plants are establishing, and was observed via dieback of leaves present at planting (Harris et al. 2005). However, Mackay et al. (2002) considered P. tenax suitable for revegetation projects at exposed sites because of its high water-absorbing, deep rooting qualities once established. General regression analysis of distribution patterns in relation to environmental variables for P. tenax indicates a broad tolerance of water deicit in the root zone (Wehi 2006). although frost tolerance was investigated in some Phormium cultivars by Warrington & Stanley (1987), these were ornamental varieties of probable hybrid origin. Sparrow (1965) suggested that South Island plants have more rigid leaves and stronger ibres as a result of cold winters. experimental plantings at sites throughout New Zealand demonstrated that leaf length growth was reduced during the cooler winter months except in the far north (kaitaia) (Harris et al. 2005). The regeneration of P. tenax from the stem bases has been recorded after severe frost (Terry 1999 in Bannister 2003), but a comparison of the environmental proiles of P. tenax and P. cookianum suggests that P. cookianum is more tolerant of frost and lower average temperatures (Wehi 2006). Environmental range early records of P. tenax identify hills and valleys as suitable habitat. Critchield (1951) reported that P. tenax grows naturally in a wide range of soils and topography, from sea level up to approximately 1300 m. Features which may restrict distribution include drainage and water table (Duncan et al. 1990; Harris et al. 2005) and rainfall (Critchield 1951). although P. tenax responds well to lowing water and is not disturbed by periodic looding, both waterlogging and drought have negative effects (Harris et al. 2005). Drainage is important to its growth (Wardle 1991), but it is present, although stunted, in stagnant areas. observations from the early 19th century Edaphic range although P. tenax is recorded from infertile sites, experimentation suggests that rich, well-drained alluvial and peat soils encourage abundant growth (easterield et al. 1929; Rigg & Watson 1945). Wardle (1991) considered soil fertility an important factor in predicting P. tenax abundance throughout the country. P. tenax typically dominates fertile lowland swamps on mineral or peat soils (Duncan et al. 1990; Wardle 1991; Clarkson 2002). Soil composition affects P. tenax growth, so that although P. tenax may be scattered across many wetlands with low nutrient status, plants tend to be tall but narrow (as opposed to the usual dense clumps) (Johnson & Brooke 1989; Johnson 2001). Phormium tenax was DISTRIBUTION 530 most commonly found in estuarine areas in south Westland with a high organic content and conductivity, as well as high Na and k (Dickinson & Mark 1999). on Stewart Island, P. tenax (and other species that require moderate nutrients) is restricted in distribution although present in a range of habitats, from coastal and low altitude scrub margins, shrublands, dune hollows, and Chionochloa rubra tussockland, to swamps and marshes (Wilson 1987). Species such as raupo (Typha orientalis) that require more nutrient-rich soil are lacking completely there. The Stewart Island soil in these communities has poor drainage and is peaty, with a cloudy wet climate and low evaporation. experimental work has demonstrated the beneicial effects of phosphate on growth. In pakihi (low pH, wet herbaceous heathland) soil, the application of phosphate, and also potassium when applied with phosphate, at planting resulted in marked improvement in root and leaf development (Rigg & Watson 1945). a similar result was obtained when a dressing of lax refuse was applied, suggesting that the traditional Maori practice of returning unwanted leaf material and refuse to the base of the plant may indeed have beneicial effects. More recently, Harris et al. (2005) reported that phosphate deiciency limits P. tenax growth. However, despite its preference for fertile sites, P. tenax is not limited to these conditions. For example, P. tenax can tolerate an acid soil deicient in lime (Rigg & Watson 1945). Water depth is another determinant of P. tenax distribution. using three experimental depth treatments, Sorrell et al. (2001) showed that only 60% of P. tenax survived when the water was at substrate surface level, and none survived when water was 20 cm above the substrate surface. However, when water was 10 cm below substrate surface all plants survived. Deeper water also reduced new shoot growth and height in P. tenax. The low survival and reduced growth of P. tenax in deep water is consistent with poor aeration capacity related to a low root porosity of 11%, and absence of pressurised gas low in shoots resulting in low oxygen levels at the rootshoot junction (Sorrell et al. 2001). This decreases the tolerance of P. tenax to deep standing water and prolonged looding. PLANT COMMUNITIES Plant communities dominated by P. tenax relect topography, drainage, and substrate. Here, we consider P. tenax as a signiicant component of three main New Zealand Journal of Botany, 2007, Vol. 45 community classes: coastal cliffs, slopes, and dunelands; estuarine shrublands; and lake margin and freshwater communities. Coastal cliffs, slopes, and dunelands Phormium tenax is common in coastal cliff and coastal slope communities. at its northernmost location on Norfolk Island, it grows on grassy slopes and cliffs and dry bare hillsides (laing 1914). In Taranaki, P. tenax is dominant on steep coastal cliffs with taupata (Coprosma repens) and occasional kawakawa (Macropiper excelsum), hangehange (Geniostoma rupestre var. ligustrifolium), and mahoe (Melicytus ramilorus) from Waitara to opunake on lahar deposits (Bayfield & Benson 1986). In contrast, P. cookianum is found to the north and south, mainly on mudstones. at Te Maika headland in the Waikato (PMW pers. obs.) and on the east coast near Wairoa P. tenax occurs with Hebe spp. in a laxland-shrubland on an exposed limestone/cliff face (Whaley et al. 2001). other species on these east coast bluffs include rangiora (Brachyglottis repanda), Geniostoma ligustrifolium, tutu (Coriaria arborea), wineberry (Aristotelia serrata), and Jovellana sinclairii. Phormium tenax is prevalent on coastal sites on offshore islands, from north to south. These include cliff faces on islands in the Hauraki Gulf where Hebe stricta, H. pubescens, Poa anceps, Astelia banksii, and the renga lily (Arthropodium cirratum) are present (esler 1978a). likewise, P. tenax is an important canopy plant in Coprosma repens scrub (that also contains emergent karo (Pittosporum crassifolium) and ti kouka (Cordyline australis)) on small islands off the Taranaki coast (Bayield & Benson 1986). Phormium tenax thickets were also reported in conjunction with pukanui (Meryta sinclairii) wind-shorn coastal forest in the Three kings Islands (Brook 2002). although P. tenax and P. cookianum are both present in coastal cliff communities, they generally have distinct distributions and occur together infrequently. Phormium cookianum forms communities on, for example, steep eroded cliffs in eastern districts (Clarkson & Clarkson 1991; leathwick et al. 1995), Wellington (PMW pers. obs.), and on rock outcrops in the Herangi range in the western Waikato, where karamu (Coprosma robusta) and Hebe stricta are associates (Regnier et al. 2003). Near Wairoa, P. cookianum is also present on bluffs as part of a wharariki-tuhara (Machaerina sinclairii) laxland and Hebe stricta-Brachyglottis repanda shrubland (Whaley et al. 2001). The different requirements Wehi & Clarkson—Biological lora of NZ: Phormium tenax of P. tenax and P. cookianum may relate to speciic habitat requirements, including drainage and drought tolerance, but need further study. Phormium tenax is very tolerant of salt spray, especially beyond the seedling stage (Sykes & Wilson unpubl. obs. in Wilson & Cullen 1986). However, recolonising ability may be important, especially after major disturbance. Phormium tenax occurs in coastal grasslands. Cortaderia richardii and Chionochloa conspicua tussockland is prevalent on coastal slopes on Stewart Island sheltered from south and west winds where ire or coastal dieback has removed forest cover. These large tussocks are associated with either P. tenax or P. cookianum (Wilson 1987). Cockayne (1919a) recorded P. tenax in the Chionochloa rubra grasslands in Southland, with Astelia montana, Gaultheria spp., and Blechnum penna-marina also present. These tussocklands were almost at sea level, and he noted their drought tolerance and abilities to persist in challenging conditions. P. tenax wet grassland may succeed Sphagnum bogs in Southland (Cockayne 1919a). Phormium tenax is abundant on consolidated dunes and cliffs on kaipara Peninsula (BDC pers. obs.). Phormium tenax is also an important part of dry duneland communities in some areas. In Westland, P. tenax occurs on active dunes and beach ridges with species such as marram (Ammophila arenaria), Zoysia minima, gorse (Ulex europaeus), and Carex pumila (Wardle 1991). In coastal dune grassland P. tenax was found with Ulex europaeus, Carex lagellifera, C. testacea, and other species typical of drier conditions (Wardle 1991). Moreover, although P. tenax favours good drainage it does not require a lot of soil depth (Duncan et al. 1990), allowing colonisation of poorly drained sites such as dune hollows, and persistence within mixed P. tenax shrubland communities. Near Gisborne, a small brackish wetland that lies in a dune hollow includes Juncus maritimus var. australiensis, Leptocarpus similis, Baumea articulata, Cyperus ustulatus, P. tenax, and Cordyline australis along with adventives such as willows (Salix spp.), blackberry (Rubus fruticosus), and poplars (Populus spp.) (Whaley et al. 2001). P. tenax is part of a Typha orientalis-P. tenax reedland aggregation in dune hollows at Whangaparaoa Beach on the east coast of the North Island (Regnier et al. 1988). Wardle (1991) described dune vegetation at Waitangiroto in Westland that conforms to that of a freshwater wetland (probably in part because of the high rainfall), with P. tenax, Blechnum penna-marina, Polystichum 531 vestitum, Pteridium esculentum, Rubus schmidelioides, Acaena anserinifolia, Meuhlenbeckia australis, Carex coriacea, and Cordyline australis all components of the community. Cockayne’s (1919a) description of sand shrubland in the auckland region included P. tenax along with manuka (Leptospermum scoparium), Cordyline australis, Cortaderia fulvida, Pomaderris phylicifolia, Leucopogon fasciculatus, Kunzea ericoides, Carmichaelia australis, Ozothmanus leptophyllus, and other species. Phormium tenax is, thus, tolerant of a wide range of coastal conditions occupying sites including exposed cliffs, slopes, and dunelands. Nevertheless, many coastal habitats do not support Phormium, such as the Catlins, otago (Wilson & Cullen 1986). Further research is required to clarify the factors favouring P. tenax presence and abundance in coastal areas. Estuarine shrublands Phormium tenax occurs in estuarine shrublands in the high tide area. although estuarine communities are inluenced by tidal inundation, plant communities become progressively more herbaceous and lower in stature as tidal inundation increases in frequency (Dickinson & Mark 1999). In south Westland, P. tenax occurred towards the freshwater end of an estuarine gradient (Dickinson & Mark 1999) and associated most commonly with Cortaderia richardii and Bulbinella modesta. it is also associated with Leptocarpus and woody species such as Coprosma propinqua, Myrsine divaricata, saltmarsh ribbonwood (Plagianthus divaricatus), and Hebe elliptica as well as Lepidosperma australe, Festuca arundinacea, Carex coriacea, C. virgata, Cortaderia richardii, and some characteristic smaller herbs (e.g., Bulbinella modesta, Leptinella dioica, Apium prostratum, Isolepis habra, and Juncus planifolius). Robertson et al. (1991) described a Westland coastal lagoon with Leptospermum-Phormium shrubland, and Baumea tenax, Leptocarpus similis, and occasional tree seedlings. on Stewart Island, P. tenax occurs in two main types of shrubland on the fringes of the saltmarsh: Plagianthus divaricatus shrubland at the upper limit of high tide, and Coprosma propinqua coastal shrubland in the very narrow transition area between saltmarsh and forest, found in sheltered estuaries and the heads of bays (Wilson 1987). The saltmarsh ribbonwood community is very localised at four places on Stewart Island, in a banded sequence of communities with Leptocarpus similis sedgeland on the low tide side, and Coprosma propinqua shrubland further 532 inland (Wilson 1987). at Maungawhio lagoon near Gisborne, a saltmarsh ribbon community on the dry outer edges of the lagoon consists of low patchy shrubland with Plagianthus divaricatus, Muehlenbeckia australis, Rubus fruticosus, Pteridium esculentum, P. tenax, and Cordyline australis (Whaley et al. 2001). although present in estuarine settings, P. tenax is only abundant where the freshwater inluence dominates, either through high rainfall or in groundwater. Lake margins and freshwater wetlands lake margin vegetation with abundant P. tenax has mainly herbaceous associates. In Tiniroto inland from Wairoa, P. tenax occurs in Typha orientalis reedlands on lake margins with Carex spp. and Juncus spp. (Whaley et al. 2001). Typha orientalis reedland is the most common vegetation type on the margins of the Rotorua lakes, but lake margin swamp species include P. tenax (Beadel & Shaw 1991). Swamps are sparse on the margins of lake Taupo, except at the south-eastern shore around Stump Bay (elliott et al. 1999). Pure P. tenax laxland (one of 12 swamp types) covers around 134 ha with plants of up to 3–4 m tall (elliott et al. 1999). The plants are normally emergent above up to 0.8 m water depth, and often grow on pedestals with the roots above the water level. Scattered rare associates are Carex secta, Cortaderia toetoe, and Salix cinerea (elliott et al. 1999). Phormium tenax (with Carex secta) fringes lakelets such as those on the slopes of Mt Taranaki; e.g., lake Dive at 804 m a.s.l. luxuriant P. tenax was recorded along with Carex secta and Nasturtium aquaticum in water up to at least 2 m deep at kakapo mire in Southland (Burrows & Dobson 1972). lake margin vegetation frequently forms distinct vegetation bands, with woody species appearing on drier ground. at lady lake, north Westland, Drake & Burrows (1980) reported the gradation of rushes and sedges nearest the open water through periodically looded tall herb and shrub stands into tall forest on dry land. Eleocharis sphacelata and some Baumea rubiginosa occupied the zone nearest to the open water, giving way to Typha orientalis, followed by a band of P. tenax with Carex secta and Leptocarpus similis as associates. Coprosma tenuicaulis, C. propinqua, Rubus schmidelioides, Astelia grandis, and Uncinia uncinata all occurred in the driest vegetation zone. at another small lake, Typha orientalis reedland grades into a Leptospermum scoparium sedgeland with swamp kiokio (Blechnum minus), Pteridium esculentum, and patches of P. tenax. Near New Zealand Journal of Botany, 2007, Vol. 45 Wairoa, Typha orientalis reedland also occurs, with clumps of Carex secta, P. tenax, willows (Salix spp.), common water milfoil (Myriophyllum propinquum), and various Juncus spp. (Whaley et al. 2001). In Moutoa swamp, Manawatu, free water dominated by Carex secta changed sequentially to swamp edges with Typha orientalis, P. tenax, swamp scrub of Cordyline australis and Coprosma spp., and then to semi-swamp kahikatea (Dacrycarpus dacrydioides) and pukatea (Laurelia novae-zelandiae) forest, with drainage and water depth important drivers of this ecological gradient (Poole & Boyce 1949). Similarly, esler (1978b) indicated zonation patterns at Pukepuke lagoon in the Manawatu, with P. tenax present in the more open and possibly drier stands of Typha orientalis. Phormium tenax occurs widely in freshwater communities. In the western Waikato, freshwater wetlands are dominated by alluvial lats with Dacrycarpus dacrydioides, waiwaka (Syzygium maire), Cordyline australis, and Laurelia novae-zelandiae. These are interspersed with areas of sedges, rushes, P. tenax, and reeds (Regnier et al. 2003). on the east coast of the North Island, P. tenax occurs in association with Carex and Juncus spp. in lake margin sites and as a main component within the coastal zone in swamp vegetation at low altitude, on poorly drained sites (Clarkson et al. 1986). The swamp vegetation dominated by P. tenax is one of four freshwater swamp communities recorded in this area. Phormium tenax occurs on the east coast of the North Island. unusually, however, P. tenax does not feature in any of the major vegetation types around Gisborne, although it is recorded as present. It appears to be largely absent from freshwater vegetation and Typha orientalis reedland, perhaps because there are few remaining freshwater wetlands in the district (Clarkson & Clarkson 1991). In contrast, near east cape, P. tenax occurs as a main component within the coastal zone in swamp vegetation at low altitude, on poorly drained sites (Clarkson et al. 1986). in Taranaki, P. tenax has been recorded in egmont National Park in lowland mires (Clarkson 1986). Phormium tenax is abundant on the west coast of the South Island, especially in lowland fertile swamps. In south Westland, P. tenax laxland is found, with P. tenax up to 3 m tall, and Leptospermum scoparium, Coprosma spp., Astelia grandis, and Carex spp. being some of the associates (Duncan et al. 1990). Water low and fertility are important to the abundance and growth of P. tenax, as demonstrated on Mt Taranaki. In a large lowland mire (Potaema bog) on Mt Taranaki, scattered P. tenax co-exists with Wehi & Clarkson—Biological lora of NZ: Phormium tenax a sparse cover of Leptospermum scoparium and a mixture of rushes and sedges (Clarkson 1986). However, the Denbeigh Road bog on Mt Taranaki is more fertile, with a substantial water low, and is dominated by P. tenax, Gahnia xanthocarpa, and Astelia grandis. Similarly, moderately fertile mires in the Rotorua district are characterised by P. tenax, Carex secta, C. virgata, Baumea rubiginosa, and shrubs such as Leptospermum scoparium and Coprosma tenuicaulis, but, as fertility increases, Typha orientalis often becomes more prevalent. Hence, highly fertile mires near Rotorua tend to be dominated by Typha orientalis but may also contain P. tenax, Coprosma tenuicaulis, C. robusta, and Dacrycarpus dacrydioides (clarkson & clarkson 1991). Some lowland swamps may be dominated by P. tenax, Carex spp., and Astelia grandis but lack woody species (Miller 1930; Wardle 1991). at south-eastern lake Taupo, P. tenax was a conspicuous element of Baumea rubiginosa reedland, but also present in introduced treeland dominated by Salix fragilis or Rubus fruticosus scrub, lining the levees along the channels of the Tongariro delta and other rivers. Shrub species characteristic of a less acidic and more eutrophic system, including three Coprosma species and Hebe paludosa, were dominant in a riverine back swamp in Westland (Markey & de lange 2003). Riverine delta back swamps adjacent to lake Te anau have extensive areas of P. tenax along with Carex secta and C. virgata, scattered shrubs such as Leptospermum scoparium and Coprosma propinqua, and isolated trees (Mark et al. 1972). at lake Manapouri, P. tenax occurs in shoreline bog communities formed in large ice-gouged hollows (Johnson 1972). other characteristic species of these bog communities include Leptospermum scoparium, Dracophyllum, sedges, rushes, Gentiana grisebachii, Centella uniflora, Drosera, and Haloragis micrantha. Swamps may develop in former stream courses. Inland from Gisborne, for example, P. tenax and Hebe stricta are abundant in Typha orientalis reedland (Clarkson et al. 1986). Phormium tenax also occurs in Typha orientalis-Coprosma tenuicaulis reedlands on poorly drained alluvial lats, for example at Rereauira on the east coast of the North Island (Regnier et al. 1988). Dacrycarpus dacrydioides forest occurs on better drained sites. Similarly, in the Manawatu, P. tenax and Typha orientalis illed large depressions between narrow levees on the lower Manawatu River, with Dacrycarpus dacrydioides on the higher ground (Poole 1946; Poole & Boyce 533 1949). The east Cape Pukeamaru wetlands are loristically diverse, with species such as Epilobium pallidilorum and Sparganium subglosum which are uncommon in the district (Regnier et al. 1988). Thus, in non-swamp areas, P. tenax remains strongly associated with herbaceous sedges and grasses, but some woody species also establish. Cordyline australis is a common associate of P. tenax in some lowland wetlands. Duguid (1990) described a characteristic “relict swamp” type in the Horowhenua, with P. tenax, Carex secta, Cortaderia toetoe, Cordyline australis, Astelia grandis, and a notable woody component consisting of Hebe stricta, Leptospermum, Coprosma spp., and Olearia spp. In Taranaki, Bayield & Benson (1986) described a lax tussockland-swamp on the edge of stream channels, swamps, and ponds, with Coprosma robusta, Cordyline australis, Carex virgata, Baumea rubiginosa, and Blechnum minus around the edges, and a ground cover of lax litter. on Tiritiri Island, P. tenax and Cordyline australis were conspicuous in a few alluvial creek beds, although they were generally a more scattered part of the lora (esler 1978c). Cockayne (1919a) described swamp on shingle river beds with a similar composition. Fens are mature wetlands with lower fertility than those described above. In the Waikato, these fens may be dominated by a mixture of woody and herbaceous species. Common fen species include sedges such as Baumea spp., Gleichenia dicarpa, Leptospermum scoparium, Coprosma tenuicaulis, and Cordyline australis (Clarkson 2002). Phormium tenax may also be present, but less luxuriant in growth than in high fertility wetlands. Phormium tenax has also been recorded as a signiicant component of one of ive types of swamprestiad bog on a gradient in the Chatham Islands (Clarkson et al. 2004), forming 21% of the cover, in association with Leptocarpus similis and Sporandanthus traversii. This group had relatively high pH and nutrient and moisture contents but lower total C levels and lower bulk density than other groups. Phormium tenax was rare in all other association groups (Clarkson et al. 2004). Phormium tenax is, thus, a well recognised element of freshwater wetlands and, in particular, freshwater swamps. Freshwater wetland habitats with periodic looding or stream channels for nutrient and water supply are more suitable for the establishment and growth of P. tenax. Freshwater swamps are primarily herbaceous, with sedges a common element to many, and woody species an important component in some. 534 SUCCESSION Succession after ire Phormium tenax is one of a few New Zealand plants that recover well after ire. Regeneration of P. tenax has been recorded within four months of fire at ocean Mail, Chatham Island (Clarkson et al. 2004). after a ire in awarua Bog, Southland, almost all P. tenax appeared to survive in both sphagnum bog and Chionochloa tussockland, regenerating from basal stubble to achieve nearly 30 cm of new leaf growth after 4 months. However, maximum foliage height increased only gradually to a maximum height of 180 cm after 10 years and maximum cover of 2% in the sphagnum bog (Johnson 2001). although sprouting was the main strategy, further recolonisation also occurred from windblown and soil sources of seed. Dobson (1979) reported that where lowland forest mires (such as Dacrycarpus dacrydioides forest which had P. tenax as part of an understorey) were burned, P. tenax was able to colonise through both rhizatomous and seed growth and become dominant. These successional processes have been used to advantage by Maori. Vegetation records from 19th century european settlers in Taranaki describe a modiied coastal strip 4–5 m wide mostly covered in Pteridium esculentum fernland and P. tenax as well as mixed canopy scrub that included Corynocarpus laevigatus, P. tenax, Cordyline australis, and other species (Bayield & Benson 1986), providing access to staple food and ibre plants. Succession after drainage and clearance Phormium tenax distribution has changed dramatically from the time of widespread european arrival in the 19th century. Manipulation of the environment, often with economic motives, has resulted in increased populations of P. tenax. although hill stands generally remained in their “natural state”, swamp areas were often drained in the late 19th and early 20th centuries in particular, encouraging pure dense stands of P. tenax suitable for commercial harvesting (Miller 1930; esler 1978b; Ravine 1995). For example, human disturbance increased P. tenax dominance in wetlands on the Manawatu Plains (Ravine 1995). These stands of P. tenax induced by drainage of Typha orientalis dominated areas could be maintained by regulation of the water table. Drainage has however also allowed the invasion of adventive species such as Festuca arundinacea, Rubus fruticosus, and Salix fragilis (atkinson 1922; Poole & Boyce 1949; esler 1978b). The densely tufted New Zealand Journal of Botany, 2007, Vol. 45 habit of P. tenax seems associated with longevity, and probably confers a competitive advantage so that P. tenax is not readily invaded and displaced (Wardle 1991; Jesson et al. 2006). Pure P. tenax stands are rare now through much of the country, with most having been converted into farmland. Smith (1957) reported that felling swamp forest in many places also resulted in stands of P. tenax on the undrained land, and believed that many of the vast P. tenax swamps of the late 19th and early 20th centuries resulted from the felling of these forests; for example, Dacrycarpus dacrydioides communities were probably extensive in the western Waikato prior to milling in the 19th century (Regnier et al. 2003). It seems likely that human disturbance, causing increases in sedimentation and nutrient input, has increased the relative abundance of Typha orientalis in the east Cape region (leathwick et al. 1995). Heginbotham & esler (1985) recorded P. tenax in scattered wet patches mainly near the coast in the eastern Bay of Plenty from opotiki to east Cape. Here, wetlands were probably never extensive. It is thought that many wetlands would have supported forest with tree species such as Dacrycarpus dacrydioides and Laurelia novae-zelandiae that are tolerant of wet soils, although P. tenax and Typha orientalis would have covered the wetter, more fertile sites (leathwick et al. 1995). Long-term succession as wetland conditions become more acidic and less fertile over time, fertile swamps tend to be succeeded by peat domes and bogs where P. tenax is rarely found, and it is replaced by less nutrient-demanding species (Clarkson 2002). Peat forms wherever the substrate is more or less permanently waterlogged and may be under water or built up as bogs or fens (Davoren 1978). Such swamp peatlands are widely distributed throughout New Zealand. In the Waikato, some P. tenax has been recorded at Whangamarino and Hauraki swamps where the mineral content of the swamps is higher; elsewhere it is not recorded as surface vegetation or in plant fragments in the peat layers. Maintenance of P. tenax therefore requires maintaining fertility, and the burning of peat vegetation in bogs is one method of returning these less fertile wetlands to a previous stage of succession. Development of successional phases from a Phormium-Leptospermum shrubland to forest is apparent in a coastal lagoon to forest sequence in Westland. Pedestals of turf built up around the bases of Leptospermum scoparium and P. tenax and Wehi & Clarkson—Biological lora of NZ: Phormium tenax provided sites for seedling establishment of trees species such as Lagarostrobos colensoi, Dacrycarpus dacrydioides, and Phyllocladus alpinus (Robertson et al. 1991). PESTS, DISEASES, AND ANIMAL DAMAGE Because of the export market for P. tenax ibre, studies of pests and diseases have also been important (Miller 1930; Cumber 1952; Boyce et al. 1953; Boyce 1958; liefting et al. 1997; andersen et al. 1998). For example, an outbreak of yellow-leaf disease devastated the ibre industry in the 1950s. Much of this earlier research on pests has been collated by Scheele (1997), which is useful to current resource managers of P. tenax. Miller (1930) separated the insects living in P. tenax plants into four groups. These were species which attack the leaf, the crown, and the seed, and predators and parasites. From economic and weaving points of view, however, the irst group is probably the most important as it not only has the greatest number of species, but also the species with the most damaging effects. Insect damage from the larvae of the “windower” or lax looper moth (Orthoclydon praefectata) and the lax notcher moth (Tmeolphota steropastis) is noticeable on many Phormium plants, and both can devastate large areas of laxland (Miller 1930). Scale, including Poliapsis and Pseudaulacapsis spp., and the lax mealy bug (Balanococcus diminutus) may also occur. Miller (1930) identiied two major factors which affect insect numbers. First, P. tenax which is flooded beneits from reduced insect numbers as prolonged immersion in water destroys O. praefectata larvae. Second, leaf tubes formed by dying and dead leaves act as an important shelter for the moth larvae, and were more often present in P. tenax growing in drained swamps. Miller (1930) identiied all of the insect pests as endemic. This suggests that Maori would have contended with an identical array of pests. although Miller did not mention control of pests by Maori, he considered that prior to the development of the export industry P. tenax did not seriously suffer from insect depredation, a view shared by atkinson (1921b) and others. This change appears to be linked to the changed drainage and cultivation regimes introduced with industry growth. Published records of fungi are far from comprehensive. a search of the New Zealand Fungal Herbarium database revealed 212 records of fungi on 535 Phormium tenax, from ascomycetes, Basidiomycetes, Myxomycetes, and urediniomycetes. Common fungal diseases on P. tenax include Phormium leaf mould (Periconiella phormii) and Phormium leaf spot (Glomerella phacidiomorpha and Kirramyces phormii) (Scheele 1997). Yellow-leaf disease, a major problem for the P. tenax ibre industry, was identiied as the result of a phytoplasma detected in the phloem tissue (ushiyama et al. 1969), and not a virus as previously thought. Work has continued on phytoplasmas; andersen et al. (1998) developed a method for detecting phytoplasmas that they regarded as suitable for large-scale testing of P. tenax. Phormium tenax habitat changed markedly at the start of the 20th century from wetlands to drier “induced swamps”. Commercial millers had exhausted natural stands of P. tenax and drained Typha orientalis freshwater wetlands to increase the presence of P. tenax (Cockayne 1919a; Poole 1946; Poole & Boyce 1949). Widespread commercial planting of P. tenax was required to maintain the industry, and it was believed that P. tenax growing on dry ground had better ibre (Hector 1889; Cross 1912). These monotypic stands, with resulting biodiversity loss, may have caused a change in pest abundance and distribution (e.g., Poole & Boyce 1949). Periodic looding of P. tenax stands has been recommended to reduce pests and disease (Boyce et al. 1953; Smith 1957; esler 1978b). Boyce et al. (1953) observed that rapid increase in yellow-leaf incidence frequently followed drainage of P. tenax areas. They considered that P. tenax could stand water inundation to a depth of 1 m for periods of up to four weeks in winter and would beneit from the resulting suppression of much weed and insect infestation. Smith (1957) determined that the vector insect of yellow-leaf disease in its ground-living nymph form was killed by immersion for longer than 48 hours. atkinson (1921b) also suggested that yellow-leaf is aggravated by the presence of stagnant water around plants. Furthermore, Matheson (1963) observed that although Moutoa swamp in the Manawatu used to be looded approximately four times a year, looding was, at that time, negligible, something that led to dificulties in the growing of P. tenax. The lowered water table led to the death of the natural swamp P. tenax and planting of another cultivar that tolerated the drier conditions. Phormium tenax is susceptible to browse by a range of introduced animals including sambar deer (Stafford 1997) and cattle (Hector 1889). 536 Cattle trampling on the roots may also result in stunted plants (esler 1978b). OTHER BIOTIC RELATIONSHIPS Phormium tenax provides food for a number of native animals. Geckos have been encountered among Phormium lowers (Towns 1994), and lax nectar was recorded as the most important food for breeding tui in the Chatham Islands (Dilks et al. 1998). similarly, P. tenax seed is also an important food for birds such as red-crowned kakariki (Cyanomorphus novaezelandiae), consisting of up to 17% of food eaten in late summer and autumn on Tiritiri-Matangi Island (Dawe 1979). Instances of birds ripping ripe seed pods to access seeds have been reported (Dawe 1979 and references therein). Phormium tenax acts as valuable habitat for native fauna. The salticid jumping spider Trite planiceps builds nests in the dark cavities formed by desiccating rolled-up leaves (Forster & Forster 1973). It has adapted its hunting and mating behaviours to the lax leaf environment and hunts and interacts with conspeciics on the surface of lax leaves (Taylor & Jackson 1999). Brook (2002) recorded the only remaining habitat of the endangered giant land snail Rhytidarex buddlei on South West Island in the Three kings Islands as Phormium thickets and mixed laxbroadleaved shrubland. Thickets of large plants were noted as growing on boulder talus beneath light gaps and on the seaward edge of this forest. TRADITIONAL AND HISTORIC USES AND CULTIVATION Phormium tenax is the most common weaving plant currently used by Maori, and was in widespread use at the time of european contact in the late 18th century (Buck 1926). It is widely known to Maori as harakeke, or korari in the northern part of New Zealand, although other names have also been recorded (Beever 1991). korari is also the most common term for the lower stalk, while the seed capsule is called the kurawaka (Beever 1991). entire leaves and extracted leaf ibre are used for traditional weaving (Best 1898; Buck 1911, 1923). Historically, the leaf was plaited into many different items such as mats, receptacles, and bags, many of which continue to be made today (e.g., Pendergrast 1975; PuketapuHetet 1989). The ibre (muka or whitau) was woven into traditional clothing and nets, and this art has New Zealand Journal of Botany, 2007, Vol. 45 undergone a recent revival (Te kanawa 1992). The sclerenchyma ibre is stripped from the leaf with either a knife or mussel shell, separating the epidermis from the sclerenchyma. Maori distinguish between harakeke and wharariki, generally thought to correspond to P. tenax and P. cookianum, respectively. However, the origins and use of the name wharariki prior to the 20th century are less clear (Wehi & Clarkson unpubl. data). Maori developed a classiication system of Phormium cultivars, thought to be based primarily on the strength and quality of ibre (Cross 1912; Heenan 1991). Maori have identified particular cultivars of Phormium for different uses based on these qualities (Hector 1889; Buck undated; Cross 1912; Harris & Woodcock-Sharp 2000; Scheele 2005). Some 19th century writers such as kelly (1866) provided examples of cultivars which represented Tihore or other classes of P. tenax. around 80 Phormium cultivars valued by Maori have been collectively identiied. These have been listed by the Flax Commissioners (anon. 1871), Selwyn (1847), Moore (1849), kelly (1866), Hector (1889), Best (1908, 1942), and others. unfortunately, the vast majority of cultivars listed are mentioned only once or twice with very little additional information. The problems of identifying cultivars precisely were remarked upon by Best (1952), who noted that names from one region may be completely different from those in another. Despite these dificulties, many traditional cultivars can be accessed from the Rene orchiston Collection at landcare Research, lincoln, and have been well described by Scheele (2005). There is general agreement amongst writers in the 19th century that the “iner” varieties of Phormium were cultivated (e.g., kelly 1866; Colenso 1880). Vegetative propagation was reported in numerous sources from different areas through much of the country (king 1793; Selwyn 1847; kelly 1866; Williams undated; Best 1908; Buck 1911; elder 1932). Moreover, Maori cultivators dispersed ramets around the country to provide high quality genetic material for cultivation (Wehi 2006). Preliminary studies of the genetic relationships of valued cultivars have been inconclusive (McBreen et al. 2003) but it seems likely that future research will determine their provenance (R. Smissen pers. comm.). Maori germination of Phormium seed and soil enrichment to encourage germination by burning brushwood above the soil have been observed but are not well known (Murray 1836). This method is similar to other seed propagation methods reported for kumara (Best 1925; Mcallum 2005). Wehi & Clarkson—Biological lora of NZ: Phormium tenax after initial european contact in the late 18th century, P. tenax was quickly identiied as a potentially valuable plant for commercial enterprise (Hector 1889; elder 1932; Best 1952). early european immigrants built upon Maori knowledge of P. tenax, particularly knowledge of the ibre, to develop an economically important export industry based on ibre extraction to make cordage (e.g., Critchield 1951). The invention of a mechanical lax stripper in the 1860s greatly increased production, although the quality was regarded as inferior (Hector 1889). exports peaked at 28 000 tonnes in 1907 and then declined as natural stands became depleted. In spite of a number of highs and lows, the industry endured for most of the 19th and 20th centuries (Poole & Boyce 1949; Critchield 1951; McCay 1952; Cooper & Cambie 1991) and swamp management and cultivation techniques were developed to improve production, especially in the Manawatu district of the North Island (Poole & Boyce 1949; Matheson 1963). although P. tenax is primarily known as a weaving plant, a number of medicinal remedies rely on its properties. use of P. tenax was an essential part of Maori daily life prior to european colonisation, with common uses including decoctions of the exudate at the leaf base (pia harakeke) applied to severe wounds, burns, old sores, and rheumatic or sciatic regions; blanched leaf bases that are sometimes pulped and then roasted to relieve tumours and abscesses; and juices from the roots drunk as purgatives (Brooker et al. 1987). other external uses include the application of warm roots to fresh cuts and ringworm, while the dressed ibre makes an excellent ibre for dressing wounds (Brooker et al. 1987). Further non-medicinal uses of harakeke include lower stalk harvesting to make rafts. The plant remains highly valued by Maori. ECONOMIC IMPORTANCE Interest in a commercial fibre industry remains strong despite previous failure to compete globally with artiicial and natural ibres. as well, the role of quality ibre in the current revival of traditional Maori weaving techniques and associated markets should not be underestimated. Phormium tenax cultivars have been extensively developed as ornamental garden plants by nurseries and growers (Heenan 1991; Metcalf 1995), with some cultivar selections protected under the New Zealand Plant Variety Rights act 1987. The seed oil is rich in the 537 essential fatty acid linoleic acid, and may be eaten as a condiment. Medicinal possibilities also continue to be pursued, and the exudate from the leaf base shows promise as a shear-thinning thickener for cosmetics (Newman et al. 2005). It may prove possible to develop seed oils for a “total utilisation” concept (Newman et al. 2005). CONSERVATION AND RESTORATION although P. tenax is well represented in protected areas such as scenic reserves and national parks throughout the country, P. aff tenax in the chatham Islands has been listed as range restricted (de lange et al. 2004). Biological invasion of freshwater wetlands by exotics is a recognised threat, with the potential for adventive species to drive succession in these communities. adventive woody invaders such as Salix spp. and Populus spp. demonstrate tolerance for wet conditions, for example, at emirau wetland north of Gisborne. located in a lat, silted valley bottom, P. tenax is present in this wetland with Coprosma robusta, Blechnum minus and B. novae-zelandiae but also Salix spp. and Populus spp. (leathwick et al. 1995). Rubus fruticosus and Ulex europaeus are other common adventives in wetland habitats. Weed invasion is common throughout much of the country, with Salix spp. of particular concern. Many of these exotic species are dificult to control or remove, and many freshwater communities will retain little native character without ongoing pest maintenance. Phormium tenax ramets are frequently used in revegetation plantings, especially along stream edges and roadsides (McGruddy 2006), and on urban restoration sites. It is widely recommended for restoration planting, partly because of its value as nesting habitat and as a food source for native birds (e.g., http://gullyguide.co.nz/iles/Gully.pdf). Plantings of P. tenax can increase survival for endangered species such as the yellow-eyed penguin, providing good nest sites for breeding (http://www.yellow-eyedpenguin.org.nz/work/habitat/index.html). Phormium tenax has potential as a nurse plant for other species (Reay & Norton 1999). CONCLUSIONS Phormium tenax is an iconic New Zealand monocotyledon that thrives in a wide range of habitats. although most commonly associated with 538 freshwater wetlands, it is present in a diverse range of habitats. These include the coastal zone, on drier sites such as cliffs, hill slopes, and dunelands, and at the freshwater end of estuarine ecosystems. It is also present in dune hollows and lakelets where the vegetation is that of freshwater wetland systems. It grows on a range of substrates from riverine alluvial lats to peaty soils. P. tenax is present in freshwater wetland communities which vary from lake margins to woody shrubland communities. although growth is best in relatively fertile sites, it is also present in less fertile sites and even relatively infertile bogs, albeit with stunted growth. Collectively its presence in these communities demonstrates the broad environmental range of P. tenax. Recent research has demonstrated the potential for scientists to work with Maori knowledge. This work, as well as the use of modern scientiic techniques, has led to new perceptions of P. tenax and advances in chemistry, taxonomic classiication, and other disciplines. However, experimental manipulation of ecological variables and further work on the environmental range of P. tenax is likely to provide new insight into this plant. Similar work on P. cookianum would allow useful comparison between the two species. Continuing interest in the cultural heritage of our native biota, new commercial developments, and its use in ecological restoration and urban planting programmes make further examination of the species necessary and timely. ACKNOWLEDGMENTS We would like to thank Carol West and Warwick Harris for valuable comments on an earlier draft of the manuscript. Max oulton kindly prepared the igure. 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