The Genus Amorphophallus - Bjorn Malkmus Rare Seed Nursery

The Genus Amorphophallus (Titan Arums) 

Origin, Habit and General Information 

The genus Amorphophallus is 

well known for the famous 

Amorphophallus titanum, 

commonly known as "Titan 

Arum". The Titan Arum holds the 

plant world record for an 

unbranched single 

inflorescence. The infloresence 

eventually may reach up to three 

meters and more in height. 

Besides this 

oustanding species more than 200 Amorphophallus species have been 

described - and each year some more new findings are published. A 

more or less complete list of all validly described Amorphophallus 

species and many photos are available from the website of the 

International Aroid Society (http://www.aroid.org). If you are 

interested in this fascinating genus, think about becoming a member of 

the International Aroid Society! The International Aroid Society is the 

worldwide leading society in aroids and offers a membership at a very 

low price and with many benefits! 

A different website for those interested in Amorphophallus hybrids is: 

www.amorphophallus-network.org This page features some awe-inspiring new hybrids, 

e.g. Amorphophallus 'John Tan' - an unique and first time ever cross between 

Amorphophallus variabilis X Amorphophallus titanum! 

The majority of 

Amorphophallus species is 

native to subtropical and 

tropical lowlands of forest 

margins and open, disturbed 

spots in woods throughout 

Asia. Few species are found in 

Africa (e.g. Amorphophallus 

abyssinicus, from West to 

East Africa), Australia 

(represented by a single 

species only, namely Amorphophallus galbra, occuring in Queensland, North Australia 

and Papua New Guinea), and Polynesia respectively. Few species, such as 

Amorphophallus paeoniifolius (Madagascar to Polynesia), serve as a food source 

throughout the Asian region. 

As in other related genera within the broad Aroid family (Araceae), such as Arisaema, 

Dracontium, and Typhonium, most species develop a large, subterranean round to vertical 

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elongated tuber or fleshy rhizome, which serves as a storage organ and may gain up to 

60kg and more in the tallest species, such as 

Amorphophallus hewitii (Sarawak, East 

Malaysia), Amorphophallus titanum (Sumatra, 

Indonesia), and Amorphophallus gigas 

(Sumatra, Indonesia). In most species a single, 

long-stemmed, umbrella-like, dissected leaf is 

developed during each growing cycle. This single 

leaf resembles almost a small tree in the above 

mentioned giant members within the genus. In 

certain species, such as Amorphophallus 

bulbifer (widespread throughout India), a 

secondary leaf may develop under favorable growing conditions. Seedlings and young 

plants received via in-vitro propagation or by means of leaf cuttings tend to make several 

subsequent leaves before they will enter their true first dormancy period. 

On maturity, plants usually produce a single inflorescence before the leaf unfolds. Few 

species may develop several inflorescences per tuber (e.g. Amorphophallus 

polyanthus) and/or make their inflorescence after laf development. Some 

Amorphophallus species will rest for an entire year after flowering, i.e. they will skip one 

growing cycle. The inflorescence is composed of a sometimes very colorful outer spathe (a 

pseudo petal) and an inner spadix. The spadix may be shorter or protruding the spathe, 

and usually has a different color. The spadix hosts quite small male and female flowers at 

its base. The upper part (e.g. the spadix appendix) is usually the only visible part of the 

spadix. On the day of opening the female flowers are receptive and the spaidx releases a 

sometimes very unpleasant strong scent, which is very attractive for its main pollinators, 

such as flies, and certain beetles. On the second day (or later) the female flowers are not 

receptive anymore, whereas the male flowers release their pollen. Thus one would usually 

need two inflorescence at more or less the same time in order to successfully transmit 

polen from a first inflorescence to a second flowering plant. Few species are apomictic and 

may set viable seeds without pollination (e.g. Amorphophallus bulbifer, 

Amorphophallus henryi, Amorphophallus kiusianus, and Amorphophallus muelleri). 

After successful pollination the female flowers develop into some colorful berries, which 

may contain one to rarely two or three seeds each. In most species berries are bright 

orange to scarlet, whereas some may be bluish-lilac (e.g. Amorphophallus kiusianus 

from South Japan, East China, and Taiwan) or rarely whitish-green to yellowish-green. 

The ovate to elliptic berries are somewhat fleshy and are mostly dispersed by birds. 

Cultivation 

In cultivation, most species are easily grown in any humus-rich, organic, very well drained 

and well aerated soil. The majority of Amorphophallus species can be grown at some 20°C 

(optimal 25°C) during summer in a semi-moist soil in a partially shaded spot with 

protection from direct sunlight, especially during hours at midday. Few tropical species, 

such as the famous Amorphophallus titanum from Sumatra, require an overall higher 

average temperature of some 25°C throughout their entire growing cycle and during 

dormancy as well. Few species (mostly the beforehand mentioned tropical species) have a 

prolonged growing cycle which exceeds 12 months, or they may be even evergreen (e.g. 

Amorphophallus coaetaneus). However most species will follow seasons and their 



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single leaf will yellow from late 

summer to early winter. At this 

point, plants should be kept 

drier at a minimum of some 

15°C. Tropical species require a 

higher temperature and very 

careful watering during 

dormancy. It is not essential, 

that dormant tubers are kept 

completely dry, but soil should 

not be soaked wet at any time 

during dormancy. As a matter of fact, a dry storage will inevitably lead to losses in most 

tropical species. However, most African species from seasonally dry areas (e.g. 

Amorphophallus andranogydroensis, Amorphophallus consimilis, and 

Amorphophallus dracontioides) are best kept completely dry during dormancy. 

Formerly, Amorphophallus species had been separated into two distinct cultivation groups 

with different cultivation requirements concerning soil composition, minimum temperatures 

and water suppply during dormancy. On grounds of some more recent and more detailed 

cultivation experiences, most species can be successfully grown in one and the same soil 

mixture (see above). Different temperatures are not necessary during dormancy either. 

However, several highland species will come into growth earlier, probably in mid winter 

already, and hence they will require artificial light. It is not necessary either to keep soil 

completely dry during dormancy. Several species will show less vigor and minor growth, if 

the tuber is kept completey dry during dormancy. In most species, a slightly moist soil will 

be suitable (with exception for a couple of more delicate African species). As a general 

rule: the moister the soil, the higher temperatures have to be during dormancy. Tropical 

species require a temperature optimum of not below 25°C throughout the year, whereas 

some 15°C to 20°C are sufficient for all other species. 

Most tubers stay dormant for some 3 to 7 months. Increasing temperatures during daytime 

stimulate new growth in most Amorphophallus species from spring to mid summer. 

Tropical species are less predictable concerning their growth cycle and may well come into 

growth at any time of the year. Thus artificial light during winter months and heat are 

essential factors to successfully cultivate these species. As soon as the new leaf appears 

from the center of the tuber, plants shall be watered carefully on a more regular basis and 

feeded weekly till mid summer with any common fertilizer. Roots are developped primarily 

from the upper part of the tuber in most species, thus the tuber shall be planted deep 

enough, so that the roots may develop freely. Three times the size of the tuber is a 

suitable depth for most species.The tuber in immature specimens may increase its weight 

threefold or even more in a single season, hence the growing pot has to be of an adequate 

size to fit the newly developping tuber. 

Propagation by Seeds 

Most Amorphophallus are extremely easily raised from preferably fresh seeds. If seeds 

cannot be sowed immediately, they may be stored for some weeks or months. Seeds from 

Amorphophallus kiusianus and Amorphophallus konjac showed still good germination 

rates after more than 12 months storage at 7°C in semi-moist peat moss. However it is 



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essential that seeds are constantly kept slightly moist (e.g. in slightly moist peat moss) and 

at lower temperatures of some 10°C in order to delay the germination process. Once 

completely desiccated or frozen, Amorphophallus seeds will have lost their viability and 

they will not germinate anymore. Prior to sowing the outer flesh has to be removed by 

thoroughly rinsing it away with water. Wear some protective hand gloves, for the flesh 

contains some very irritant substances. The flesh also contains some chemical which act 

as germination inhibitors. These susbtances will siginificantly delay germination, if the 

entire berry is sowed. Seeds are potted some 1 cm deep in the same soil mix as one 

would use for ault tubers. Soil should be kept slightly moist at all times. The optimal 

temperature is some 25°C at day 

and some 20°C at night. One should 

add a couple of degrees for all 

tropical species. Most seedlings will 

occur within some 2 to 6 weeks 

(examples from the left: 6 weeks old 

Amorphophallus gomboczianus 

seedlings and 6 months old 

Amorphophallus laoticus seedlings). Some may take a couple of weeks more. Seeds of 

Amorphophallus kiusianus may well need some 6 months and more to germinate. Most 

seedlings show a prolonged growing cycle in comparison to older and mature specimens 

within the same species. Thus pots should kept warm in partial shade throughout the year 

as long as seedlings are “in green”, i.e. as long as they have a leaf. Several seedlings may 

make not only one, but two or more subsequent leaves before they enter dormancy for the 

first time. As a general rule, young dormant seedling tubers, as well as any other small 

offset tubers or leaf bulbils, shall not be kept completely dry during dormancy, as they may 

desiccate more easily. 

Propagation by Offsets & Leaf Bulbils 

Apart from seeds, most species vegetatively propagate as well. They either propagate by 

stoloniferous offsets (e.g. Amorphophallus albus, Amorphophallus antsingyensis, 

Amorphophallus bangkokensis, Amorphophallus impressus, Amorphophallus 

krausei, and Amorphophallus konjac), by small adjacent tubers (e.g. Amorphophallus 

thaiensis, Amorphophallus odoratus, Amorphophallus 

paeoniifolius, and Amorphophallus yunnanensis) or rarely 

by leaf bulbils (e.g. Amorphophallus beccarii, 

Amorphophallus bufo, Amorphophallus bulbifer [see foto 

with large central leaf bulbil and three developping adjecent 

bulbils], Amorphophallus muelleri, Amorphophallus 

yuloensis, and Amorphophallus xiei). These offsets and 

small tubers shall stay attached to the main tuber until they can 

be separated easily. Leaf bulbils can be easily separated from the leaf after the leaf will 

have withered. 



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Propagation by Leaf Cuttings 

Leaf cuttings and in-vitro cultivation are some more dedicated advanced methods of 

vegetative propagation. Whereas in-vitro propagation requires some rather expensive 

material and special techniques and experience, it is quite easy and rather inexpensive to 

take leaf cuttings, even for not that experienced private cultivators. It has to be noted, that 

not all species can be successfully propagated from leaf cuttings. For example, so far this 

method has failed in Amorphophallus konjac and in Amorphophallus paeoniifolius. 

And in those species, which can be grown from leaf cuttings, not all cuttings will eventually 

make a tuber. But for the rarer species it is quite worth the effort, especially for those, 

which do not make any offsets or leaf bulbils (e.g. Amorphophallus borneensis, 

Amorphophallus decus-silvae, Amorphophallus gigas, and Amorphophallus 

titanum). From the latter four species, Amorphophallus titanum is easily propagated via 

leaf cuttings, provided that leaflets are mature and of an adequate size. 

The following material will be necessary to take leaf 

cuttings: 

- a transparent plastic box with cover, large enough to host 

the cuttings 

- small pots with a bottom hole, pereferably transparent to 

easily control root growth 

- a sharp and clean knife and some alcohol solution for 

desinfection 

- some lables and a pencil 

- preferably some rooting hormone, especially formulated 

for leaf cuttings 

- finely granulated, clean washed pumice or any other 

inorganic small grained substrate 

A healthy leaf shall be chosen for taking cuttings. The cutting 

should be preferably made in the early morning hours, as 

long as the leaf is turgescent. The cut should be directly 

made above a branching point (see dotted red line). 

Under optimal conditions, the leaf is some 1 to 3 months old. 

Younger leaves may be too imature, whereas older leaves 

may be programmed to enter dormancy already. 

As an exception to the above rules, leaf cuttings can be 

taken at any time in a rescue try for a rare species with signs 

of a rotting tuber. It may prove easier to rescue a species by 

taking leaf cuttings instead of trying to rescue the infested 

tuber. 



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A typical cutting is some 10cm to 20cm (or more) long, 

depending on species and its size of leaflets. The cutting 

consists of at least one to three leaflets, maybe even some 

more in very small species to have a sufficiently large 

surface for photosynthesis. 

The cut should be made straight with a very sharp knife and 

without squeezing the tissue. 

As a general rule, from well grown plants 1/3 of a leaf can be 

taken. This way, the mother plant has a still sufficiently large 

leaf surface for photosynthesis and to increase its own tuber 

in size or to maintain its size. In very large mature 

specimens up to 1/2 of the leaf may be taken for leaf 

cuttings. 

In the left example of Amorphophallus macrorhizus, some 

1/4 was taken from the total leaf surface. 

In between cuttings, the knife blade should be desinfected, 

e.g. by dipping it into alcohol. Let the knife blade dry up 

before taking the next cutting. 

Preferably use a rooting hormone as directed on the 

package. Some species may be successfully propagated 

without using any rooting hormone. However, in general the 

success rate will be much lower and it may take longer for 

the cutting to make a new basal tuber. 

Do not forget to write a label for each pot in order to not get 

lost with identifications, especially if cuttings from more than 

one species are going to be taken! 

After taking the cutting, immediately dip it into the powder, 

shake off any excessive powder and plant the leaf cut 

vertically into a small pot. Depending on pot size, one or 

more cuttings will fit into a single pot (in the left example, two 

cuttings were planted). Pumice or any other inorganic 

substrate will work best. Organic substrates (such as peat 

based soils and the like) are less recommended, for these 

will usually promote bacterial and fungal growth. 



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Pests and Diseases 

Carefully place the small pot in a transparent plastic box and 

put on the cover to raise air humidity. The box should be 

large and tall enough, so that the leaflet tip will not touch the 

cover (possible rotting). Store the plastic box in a shaded 

place with some indirect sunlight at some 25°C to 30°C. 

Control humidity every other day and if necessary, mist the 

cuttings. 

Cuttings will start to produce some callus tissue after some 4 

to 12 weeks and a couple of weeks later some roots will 

form. A first small new leaf will eventually appear from the 

base of the cutting and/or the cutting will make a small 

dormant tuber before it will wither. If the leaf cutting withers 

and no new leaf has been created, carefully check its base. 

In most cases it will have made a small dormant tuber. 

Cultivation for these newly formed tubers is the same as 

mentioned above for growing seedlings. 

In general, Amorphophallus species are rather trouble-free and easy-going in cultivation, 

provided that some basic cultivation guidelines are complied. 

However, dormant tubers are sometimes prone to fungal or bacterial infections and rotting, 

especially in very moist soils and at rather low temperatures at the same time. If an 

infection is detected (parts of the tuber start to get slimy or mashy), an effort of rescue may 

be started by generously cutting away all infected parts. The rest of the tuber shall hence 

be dusted with some power fungicide and kept absolutely dry for several days before 

being repotted in a rather dry soil. In general and as a prevention measure against fungal 

infections, older plants should be kept rather dry during dormancy - with the exception of 

several tropical species, which have to be kept slightly moist throughout the year to 

prevent the tuber from dessication. If dormant tubers are stored unpotted and completely 

dry, they are more easily infested by mealy bugs. Thus a slightly moistened soil should be 

maintained in all species except for African members, which prefer a dry soil during 

dormancy. Leaves may be infested rarely with aphis and more often with spider mites. 

This especially occurs in winter months and if plants are kept at rather low air humidity 

inside the house. Any available insecticide spray respectively systemic solution fomulated 

against aphids, spider mites and/or mealy bugs will work fine. Always refer to the 

directions of use as stated on the package. And before treating an entire collection with 

some new insectide, a first trial should be made on a single plant in order to check for any 

unwanted side-effects. 

Another, and much more serious pest are nematodes. These are very small and almost 

transparent worms with some 2mm to 4 mm in length. All dormant tubers shall be repotted 

every other year and inspected for these insects. An infestation can be detected for small 

bumby warts on the outside of the tuber. These warts will eventually implode and leave 

behind a small mashy crater. This wound may be the entry site for a secondary bacterial 

and/or fungal infection. Unfortunately there is no reliable nematocide available for an use 

in a private collection. If such an infestation is detected, the best thing would be to throw 



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the entire pot (including the plant and the soil) away. For the rarer and hence pricier 

species, you may want to try to rescue the plant. However, an infested plant has to be kept 

in quarantine at all times and its pot should never get into contact with the open ground or 

a growing bench with other pots. Thoroughly wash the tuber removing any adherent soil. It 

may help to soak the tuber in some undiluted hypochlorite solution (standard bleach, wear 

some protective hand gloves for handling!) for some three minutes in order to remove 

some bacteria, fungal spores and nematodes from the tuber surface. Afterwards rinse the 

tuber thoroughly again with water to remove any remaining solution and let it dry a couple 

of days. After that repot the tuber using a new pot and fresh soil. Do not try to sterilize the 

old pot, but throw it away under all circumstances. Tuber offsets will inevitably be infested 

as well and these do not serve to regain a nematode-free stock. However, seeds, leaf 

bulbils and leaf cuttings are usually nematode-free, and this is the second-best option to 

rescue an infested plant. After successful propagation the mother plant shall be discarted 

as soon as possible. 

Plant & Seed Source 

An extensive list of Amorphophallus and other aroid species is available here: 

http://www.rareplants.de/shop 

http://www.plantdelights.com 

At present we are propagating a very good 

selection of tuber-forming aroid species within 

the following genera: Amorphophallus, 

Anchomanes, Ariopsis, Arisaema, Arum, 

Biarum, Colletogyne, Dracontium, 

Dracunculus, Gorgonidium, Helicodiceros, 

Pinellia, Pseudodracontium, 

Pseudohydrosme, Spathantheum, 

Taccarum, and Typhonium. 

Plant Delights Nursery is the best source of 

aroids and other exotic garden perennials in 

America. We have a large selection of 

Amorphophallus for sale, shipped as potted 

plants or dormant bulbs depending on season. 

You can buy a wide variety of aroids such as 

Arisaema, Arum, Dracunculus, Elephant 

Ears, Pinellia, Philodendron, Sauromatum 

and others. Visit our online plant catalog today 

to see all our new plants! 



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The Genus Amorphophallus - Bjorn Malkmus Rare Seed Nursery

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