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 3, 2026, Puget Sound stations range from 1070 to 1180.6 GDD₃₂. Quaking Aspen has reached 'flower buds visible' (902 GDD₃₂) and is approaching 'bud break', predicted around Apr 4.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,181 | 'Bud break' | 'Leaf emergence' | 236 |
| Seattle / UW | 1,171 | 'Bud break' | 'Leaf emergence' | 246 |
| Kent / Auburn | 1,111 | 'Flower buds visible' | 'Bud break' | 18 |
| Olympia / Tumwater | 1,106 | 'Flower buds visible' | 'Bud break' | 23 |
| Bellingham / Whatcom | 1,101 | 'Flower buds visible' | 'Bud break' | 28 |
| Tacoma / Puyallup | 1,075 | 'Flower buds visible' | 'Bud break' | 54 |
| Sequim / Rain Shadow | 1,070 | 'Flower buds visible' | 'Bud break' | 59 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'First bloom' BBCH '61' | 902 | '' |
| ● 'Flower buds visible' BBCH '51' NOW | 902 | '' |
| ○ 'Bud break' BBCH '07' NEXT | 1129 | '' est. Apr 4 (forecast) |
| 'Leaf emergence' BBCH '11' | 1417 | '' est. Apr 18 (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 3, 2026. Predicted dates use 16-day weather forecast through Apr 19, 2026, then climate normals.