Scouler's Willow
Salix scouleriana
Salicaceae · broadleaf deciduous tree · native
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
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.
Quick Facts
Phenological Calendar
As of April 23, 2026, Puget Sound stations range from 1434.4 to 1592.7 GDD₃₂. Scouler's Willow has passed 'leaf emergence' (1221 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 23, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,593 | 'Leaf emergence' | — | — |
| Seattle / UW | 1,554 | 'Leaf emergence' | — | — |
| Kent / Auburn | 1,537 | 'Leaf emergence' | — | — |
| Olympia / Tumwater | 1,505 | 'Leaf emergence' | — | — |
| Bellingham / Whatcom | 1,483 | 'Leaf emergence' | — | — |
| Tacoma / Puyallup | 1,472 | 'Leaf emergence' | — | — |
| Sequim / Rain Shadow | 1,434 | 'Leaf emergence' | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Flower buds visible' BBCH '51' | 757 | '' |
| 'Bud break' BBCH '07' | 894 | '' |
| ● 'Leaf emergence' BBCH '11' NOW | 1221 | '' |
GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? GDD₃₂ thresholds from USA National Phenology Network citizen science observations (WA+OR). Season tracker for Kent / Auburn as of Apr 23, 2026. Predicted dates use 16-day weather forecast through May 10, 2026, then climate normals.