Family: Salicaceae

Origin, Description & Uses
Salix cinerea (common sallow, gray sallow, gray willow, pussy willow) is a deciduous shrub or small tree native to a wide region spanning Europe, southwestern Siberia, the Caucasus, and parts of North Africa (Morocco). It typically grows in wet or seasonally flooded habitats such as stream banks, marshes, and damp woodlands. The plant is well known for its soft, fuzzy “pussy willow” catkins that appear in early spring before the leaves emerge. It has been widely used in ornamental plantings for its attractive catkins and fast growth, and in some regions has also been used for erosion control, habitat restoration in wetlands, and traditional uses such as basket weaving and small-scale woodcraft.

Risks & Threats
Although Salix cinerea is currently not known to be naturalized in the Hawaiian Islands, it possesses traits that are cause for concern in tropical island ecosystems. It grows rapidly, reproduces prolifically through both seeds and vegetative fragments, and thrives in wet habitats where it can form dense thickets. In other parts of the world, similar willow species have demonstrated invasive behavior, outcompeting native wetland plants, altering stream flow and sediment patterns, and reducing habitat quality for native species. Given Hawaii’s vulnerable freshwater and riparian ecosystems, the introduction of this species could pose a risk of ecological disruption if it were to establish. Choosing a low-risk or native alternative is strongly recommended when suitable options are available, to help protect Hawaii’s watersheds and native biodiversity.

High Risk Traits:

• Broad climate suitability
  
• Naturalized in Australia, New Zealand and possibly North America
  
• An environmental weed in Australia and New Zealand, reducing native biodiversity
  
• Other Salix species are invasive
  
• Tolerates many soil types
  
• Forms dense stands
  
• Reproduces by seeds and vegetatively by suckers
  
• Hybridizes with other species
  
• Reaches maturity in 2-3 years
  
• Seeds dispersed by wind, water, internally by horses and possibly other browsing animals, and intentionally by people
  
• Stem fragments dispersed by water
  
• Prolific seed production
  
• Able to resprout after cutting

Low Risk Traits:

• Native to temperate regions, may limit ability to invade to higher elevations in tropical island ecosystems
  
• Unarmed (no spines, thorns, or burrs)
  
• Palatable to deer, moose and potentially other browsing animals
  
• Non-toxic
  
• Dioecious
  
• Recalcitrant seeds lose viability rapidly (within 6 weeks)
  
• Herbicides provide effective control