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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.

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Common name: goat willow

Synonyms and Other Names: pussy willow

Taxonomy: available through www.itis.gov

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)

Alaska	Hawaii	Puerto Rico & Virgin Islands	Guam Saipan

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

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

References: (click for full references)

Ahmed, A., W.A. Shah, S. Akbar, M. Younis, and D. Kumar. 2011. A short chemical review on Salix caprea commonly known as goat willow. International Journal of Research in Phytochemistry & Pharmacology 1(1):17-20.

Argus, G.W. 1986. The Genus Salix ( Salicaceae ) in the Southeastern United States. Volume 9. American Society of Plant Taxonomists.

Cremer, K.W. 2003. Introduced willows can become invasive pests in Australia. Biodiversity 4(4):17-24.

Fogelqvist, J., A.V. Verkhozina, A.I. Katyshev, P. Pucholt, C. Dixellus, A.C. Rönnberg-Wästljung, M. Lascoux,  and S. Berlin. 2015. Genetic and morphological evidence for introgression between three species of willows. BMC Evolutionary Biology 15:193.

Dijkstra, J.J., J.C.L. Meeussen, and R.N.J. Comans. 2004. Leaching of Heavy Metals from Contaminated Soils:  An Experimental and Modeling Study. Environmental Science & Technology 38(16):4390-4395.

Enescu, C.M., T.H. Durrant, D. Rigo, and G. Caudullo. 2016. Salix caprea in Europe: distribution, habitat, usage and threats in San-Miguel-Ayanz, J., D. Rigo, G. Caudullo, H.T. Durrant, and A. Mauri, eds. European Atlas of Forest Tree Species. European Commission.

Eversham, B. 2006. A Key to Lowland Willows, Sallows and Osiers v. 1.6.

Frouz, J., B. Keplin, V. Pizl, K. Tajovsky, J. Stary, A. Lukesova, A. Novakova, V. Balik, L. Hanel, J. Materna, C. Duker, J. Chaluspky, J. Rusek, and T. Heinkele. 2001. Soil biota and upper soil layer development in two contrasting post-mining chronosequences. Ecological Engineering 17:275-284.

Giesy, J.P., S.A. Mabury, J.W. Martin, K. Kannan, P.D. jones, J.L. Newsted, and K. Coady. 2006. Perfluorinated Compounds in the Great Lakes. Hdb Env Chem 5:391-438.

Great Lakes Indian Fish & Wildlife Commission, (GLIFWC). Salix spp. Control. http://invasives.glifwc.org/Salix_spp/control.html. Accessed on 06/27/2017.

Hygnstrom, S.E., P.D. Skelton, S.J. Josiah, J.M. Gilsdorf, D.R. Virchow, J.A. Brandle, A.K. Jayaprakash, K.M. Eskridge, and K.C. VerCauteren. 2009. White-tailed deer browsing and rubbing preferences for trees and shrubs that produce nontimber forest products. HortTechnology 19(1):204-211.

Karrenberg, S., P.J. Edwards, and J. Kollmann. 2002. The life history of Saliacaceae living in the active zone of floodplains. Freshwater Biology 447(4):733-748.

Kay, Q.O.N. 1985. Nectar from willow catkins as a food source for Blue Tits. Bird Study 32(1):40-44.

Kuffner, M., S.D. Maria, M. Puschenreiter, K. Fallmann, G. Wieshammer, M. Gorfer, J. Strauss, A.R. Rivelli, and A. Sessitsch. 2010. Culturable bacteria from Zn- and Cd-accumulating Salix caprea with differential effects on plant growth and heavy metal availability. Journal of Applied Microbiology 108(4):1471-1484.

Kuusinen, M. 1995. Epiphytic lichen diversity on Salix caprea and Populus tremula in old-growth forests of Finland. Mitt. Eidgenoss. Forsch. anst. Wald. Schnee. Landsch 70(1):125-132.

Lowe, S., N. Repper, L. Miles, and S.G. Wallace. 2012. Notes on tree planting and the use of native species in North East England. The Wildlife Trusts, Northumberland.

Lygis, V., R. Bakys, D. Burokiene, and I. Vasilliaukaite. 2012. Chondrostereum purpureum-bosed control of stump sprouting of seven Hardwood species in Lithuania. Baltic Forestry 18(1):41-55.

Mudrák, O., M. Hermová, C. Tesnerová, J. Rydlová, and J. Frouz. 2016. Above-ground and below-ground competition between the willow Salix caprea and its understorey. Journal of Vegetation Science 27:156-164.

Palme, A.E., V. Sermerikov, and M. Lascoux. 2003. Absence of geographical structure of chloroplast DNA variation in sallow, Salix caprea L. Heredity 2003(91):5. 465-474.

Peeters, L., and Ø. Totland. 1999. Wind to insect pollination ratios and floral traits in five alpine Salix species. Canadian Journal of Botany 77(4):556-563.

Regvar, M., M. Likar, A. Piltaver, N. Kugonic, and J.E. Smith. 2010. Fungal community structure under goat willows (Salix caprea L.) growing at metal polluted site: the potential of screening in a model phytostabilisation study. Plant and Soil 330(2):345-356.

Relyea, R. 2005. The lethal impacts of Roundup on aquatic and terrestrial amphibians. Ecological Applications 15(4):118-1124.

Schutt, V.P., and H. Blaschke. 1980. Seasonal Changes in the Allelopathic Effect of Salix caprea Foliage. Flora(169):316-328.

Talbot, R.J., J.R. Etherington and J.A. Bryant. 1986. Comparative Studies of Plant Growth and Distribution in Relation to Waterlogging . New Phytologist 105:563-574.

Unterbrunner, R., M. Puschenreiter, P. Sommer, G. Wieshammer, P. Tlustos, M. Zupan, and W.W. Wenzel. 2007. Heavy metal accumulation in trees growing on contaminated sites in Central Europe. Environmental Pollution 148(1):107-114.

USDA. 2017. Plant profile for Salix Caprea (goat willow). https://plants.usda.gov/core/profile?symbol=SACA22. Accessed on 06/27/2017.

Author: Hopper, K. and R. Sturtevant

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.