Scouler's Willow
'Leaf emergence'Salix scouleriana
Salicaceae · broadleaf deciduous tree · native
Last updated
Scouler's willow is a deciduous tree native to western North America from British Columbia to California and Montana. It grows to 30 feet tall and occurs in both moist lowland and dry upland habitats, from sea level to 3000 meters, in bogs, riversides, meadows, and forest clearings. The species features yellow male catkins and brown fruit.
Hardy to zones 2a-8b, this tree tolerates sun to part shade and prefers moist soil with high moisture levels, though it adapts to a pH range of 5.0-7.0. It is fast-growing with high water needs and tolerates medium drought. Multiple diseases and pests affect this species; monitoring is important in managed landscapes.
Plant Profile
Size & Form
Site Requirements
Ornamental Interest
Uredinial Stage (Summer)
Wound Infection Window
Peak Population & Dispersal
Larval Feeding & Web Building
+ 4 more — see full disease and pest lists below
Diseases: Regionally Documented (10)
Pests: Regionally Documented (12)
Phenological Calendar
As of June 3, 2026, Puget Sound stations range from 2435.5 to 2672.8 GDD₃₂. Scouler's Willow has passed 'leaf emergence' (1221 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Jun 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,673 | 'Leaf emergence' | — | — |
| Kent / Auburn | 2,665 | 'Leaf emergence' | — | — |
| Seattle / UW | 2,610 | 'Leaf emergence' | — | — |
| Olympia / Tumwater | 2,570 | 'Leaf emergence' | — | — |
| Tacoma / Puyallup | 2,535 | 'Leaf emergence' | — | — |
| Bellingham / Whatcom | 2,533 | 'Leaf emergence' | — | — |
| Sequim / Rain Shadow | 2,436 | 'Leaf emergence' | — | — |
View full calendar (3 stages)
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Flower buds visible' BBCH '51' | 757 | '' |
| 'Bud break' BBCH '07' | 894 | '' |
| ● 'Leaf emergence' BBCH '11' NOW | 1221 | '' |
Source: 'NPN citizen science observations (WA+OR), n=5, median. services.usanpn.org' About GDD₃₂ →
Season tracker for Kent / Auburn as of Jun 3, 2026. Predicted dates use 16-day weather forecast through Jun 19, 2026, then climate normals.