Salix caprea
L.
Common Name:
Goat willow
Synonyms and Other Names:
pussy willow
Identification:
Branches of Salix caprea are hairless to sparsely pubescent and light brown in color. Branchlets differ and are chestnut brown and can range from soft and velvety to covered in long soft hairs. Leaf blades are alternate and range from narrowly to broadly elliptical in shape, they range from 15-20 centimeters in length (Argus 1986). The upper side of Salix caprea leaves are green and glossy, and the underside is covered with soft white hairs (Eversham 2006). Catkins, elongated cluster of single-sex flowers, appear in early spring before leaves. Female catkins are greenish with approximately 100-200 flowers and male catkins have yellow stamens with approximately 200-300 flowers, 5-10 catkins can be found on the majority of terminal twigs (Kay 1985). Commonly confused with Salix cinera, Salix caprea can be identified by the lack of prominent ridges on barkless wood (Argus 1986). Further causing difficulty with identification is hybridization with other members of the Salix genus resulting in descendants with intermediate traits. Morphological differences are subtle and molecular techniques are frequently needed for proper identification in the field (Palme´ et al. 2003).
Size:
Trees 12-15 m tall, Shrubs up to 8 m tall (Argus 1986)
Native Range:
Found throughout cool temperate and boreal regions in Europe and Asia (Enescu et al. 2016)
Great Lakes Nonindigenous Occurrences:
Widespread in Midwestern and Eastern USA and Canada - AL, BC, CT, DE, IL, MD, MI, NC, NS, NY, ON, OH, PA, RI, VA, WV (USDA 2017)
Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Salix caprea are found here.
Full list of USGS occurrences
Table last updated 4/27/2024
† Populations may not be currently present.
Ecology:
Salix caprea tolerates a wide variety of climates and soil conditions making it suitable for the harsh climates of northern or subalpine regions in its native range but it is intolerant of shade and requires full sun (Enescu et al. 2016). Preferred soil is calcareous but tolerant of many soils (Lowe et. al 2012). Salix caprea grows quickly in mesic to moist stands and prefers moist depressions, mire edges and spring-sides (Kuusinen 1995). However, growth is harmed by complete waterlogging of the soil (Talbot et al. 1986) and are intolerant of floodplains (Karrenberg et al. 2002). Salix caprea is also highly tolerant of fluorine (Kisser and Lehnert 1960). Reproduction takes place through pollination carried out by a wide variety of insects that includes bumblebees and solitary bees (Kay 1985). Salix caprea releases a large amount of pollen in the air when shaken and wind pollination largely influences fruit set (Peeters and Totland 1999). Contrasting other Salix species Salix caprea is not commonly propagated by fragmentation. It is a pioneer species, meaning it is among the first to colonize a damaged or disrupted ecosystem (Enescu et al. 2016). It suppresses biomass of other plants in the understory through allelopathic effects of the aqueous leachate released from leaves (Scühtt and Blaschke 1980). In addition to suppressing the growth of other species in the understory it also suppresses below-ground competition (Mudrák et al. 2016). Salix caprea is short lived and as the species declines it promotes soil formation and activity of soil fauna through organic matter additions to soil surface (Frouz et al. 2001).
The nectar and pollen of the tree are important sources of food for bumblebees and insects. In its native range Salix caprea serves as a source of nectar for Blue Tits (Parus caeruleus) (Kay 1985). Roe deer and red deer feed on the leaves and twigs of the plant (Gebczynska 1980). White-tailed deer found in the Great Lakes Region (Odocoileus virginianus) will feed on Salix caprea in low frequency (Hygnstrom et al. 2009)
Means of Introduction:
Escaped cultivation
Status:
Established
Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...
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Salix caprea has a moderate environmental impact effect in the Great Lakes.
Salix caprea is one of many native and invasive willows found in the Great Lakes Basin, all of which have similar impacts. Salix caprea is a relatively short lived willow which is easily replaced in natural succession, thus its impacts are likely minimal in undisturbed areas.
Of note Salix invasions in Australia have had negative effects on water quality and altered the physical ecosystem suggesting similar effects in the Great Lakes Basin. Dense shade created by Salix spp. negatively impacted water quality by decreasing temperature and oxygen content of water. Salix spp. also significantly altered hydrology and riparian system, underwater roots modify banks (Cremer 2003). There is little or no evidence to support that Salix caprea has significant socio-economic impact in the Great Lakes.
It has not been reported that S. caprea poses a threat to human health or water quality. There is no evidence that this species negatively impacts infrastructure, economic sectors, recreational activities and associated tourism, or the aesthetic appeal of the areas it inhabits.
Salix caprea has a moderate beneficial impact in the Great Lakes.
Salix caprea can be found for sale and is a moderately popular ornamental species.
Salix caprea contains potent antioxidants including luteolin, dihydrokaemferol and quercetin and catechin and isorhamnetin as minor constituents. Flavonoids have anti-fungal properties, includes dihydrokaempferide, naringenin, aromadendrin, taxifolin, pruning and catechin. Overall contains important constituents which have potential to treat various diseases, further review of Salix caprea could be valuable (Ahmed et al. 2011).
Salix caprea has been shown to tolerate high levels of accumulated metals suggesting high tolerance to heavy metal pollution making it suitable for phytoremediation efforts (Regvar, Likar, et al. 2010). S. caprea’s ability to accumulate heavy metals is further discussed in Unterbrunner et. al 2007 and Kuffner, De maria, et al. 2010. Heavy metals including Ni, Cu, Zn, Cd, and Pb have the potential to leach from soil to water to vary degrees (Dijkstra, Meeussen et al. 2004).
Management:
Regulations
There are no known regulations for this species Note: Illinois regulates aquatic plants that are not explicitly approved. Therefore, S. caprea is restricted in Illinois.
Note: Check federal, state, and local regulations for the most up-to-date information.
Control
Biological
Biological controls for Salix spp. are still being studied, and thus are still uncertain and need to be studied with more rigor for confident results. Application of the fungal infection Chondrostereum purpureum to Salix caprea showed little success on sprouting but formation of fruitbodies indicates possibility for enhanced sprout control. Application of 15 g of C. purpureum culture per 15 mL of media was used and applied to stumps with a paintbrush (Lygis et al. 2012).
Salix caprea is a pioneer species with a short life span and is likely to disappear in later successional stages.
Physical
Salix spp. can be cut and mowed. Trees may re-sprout from cut stumps or propagate from fragments, but this can be prevented with the application of herbicide. Mowing and weed-whackers could remove seedlings in addition to hand pulling (GLIFWC 2013).
Chemical
Nonselective glyphosate can be used on woody invasives. Tryclopyr (Garlon 3A or equivalent amine formulation) is effective for broadleaf and woody plants and will not select for grasses or sedges (GLIFWC 2013).
Apply herbicide to cut or girdled parts of trunks with brush or sponge in early fall when trees are translocating nutrients into roots. Check stumps until the stump is dead. Monitor progress over several years to remove missed seedlings (GLIFWC 2013).
Herbicides potentially have unknown toxic effects to the environment and should be used sparingly and precisely to avoid unintended damage. In aquatic habitats use herbicides formulated for use over water. Permits are required for application in Wisconsin, Michigan, and Minnesota. Check with local agencies for information on herbicide application. Follow label directions and wear proper protective clothing (GLIFWC 2013).
Note: Check state and local regulations for the most up-to-date information regarding permits for pesticide/herbicide/piscicide/insecticide use.
References
(click for full reference list)
Author:
Hopper, K. and R. Sturtevant
Contributing Agencies:
Revision Date:
10/4/2019
Citation for this information:
Hopper, K. and R. Sturtevant, 2024, Salix caprea L.: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/GreatLakes/FactSheet.aspx?Species_ID=3246, Revision Date: 10/4/2019, Access Date: 4/27/2024
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.