Quaking Aspen
Populus tremuloides
Salicaceae · broadleaf deciduous tree · native
Last updated
Populus tremuloides (Salicaceae) is a deciduous tree native across North America from Alaska to Newfoundland and south to Mexico, making it the most widely distributed tree species on the continent. It grows 40 to 50 feet tall with smooth, white to greenish-white bark and nearly circular leaves on flattened petioles that flutter ("quake") in the slightest breeze. Fall color is brilliant gold to yellow.
Quaking aspen is a pioneer species that colonizes disturbed sites after fire, logging, or avalanche. It spreads aggressively by root suckers, forming clonal colonies that can cover many acres and persist for thousands of years. It requires full sun and cool summer conditions; it struggles in lowland heat. Growth is rapid. Hardy in Zones 2a to 8b.
Quick Facts
Phenological Calendar
As of April 12, 2026, Puget Sound stations range from 1235.8 to 1375.3 GDD₃₂. Quaking Aspen has reached 'bud break' (1129 GDD₃₂) and is approaching 'leaf emergence', predicted around Apr 20.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 12, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,375 | 'Bud break' | 'Leaf emergence' | 42 |
| Seattle / UW | 1,348 | 'Bud break' | 'Leaf emergence' | 69 |
| Kent / Auburn | 1,308 | 'Bud break' | 'Leaf emergence' | 109 |
| Olympia / Tumwater | 1,292 | 'Bud break' | 'Leaf emergence' | 125 |
| Bellingham / Whatcom | 1,270 | 'Bud break' | 'Leaf emergence' | 147 |
| Tacoma / Puyallup | 1,258 | 'Bud break' | 'Leaf emergence' | 159 |
| Sequim / Rain Shadow | 1,236 | 'Bud break' | 'Leaf emergence' | 181 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'First bloom' BBCH '61' | 902 | '' |
| 'Flower buds visible' BBCH '51' | 902 | '' |
| ● 'Bud break' BBCH '07' NOW | 1129 | '' |
| ○ 'Leaf emergence' BBCH '11' NEXT | 1417 | '' est. Apr 20 (forecast) |
| 'Fall color / leaf senescence' BBCH '93' | 2294 | '' est. May 28 (avg) |
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 12, 2026. Predicted dates use 16-day weather forecast through Apr 28, 2026, then climate normals.