Quaking Aspen
Near 'Fall color / leaf senescence'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
Spring Infection Period
Spring Canker Activation
Spring Spore Germination and Infection
Crawler Emergence
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Field Observations
Phenological Calendar
As of May 13, 2026, Puget Sound stations range from 1906.2 to 2098.2 GDD₃₂. Quaking Aspen has reached 'leaf emergence' (1417 GDD₃₂) and is approaching 'fall color / leaf senescence', predicted around May 22.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of May 13, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,098 | 'Leaf emergence' | 'Fall color / leaf senescence' | 196 |
| Kent / Auburn | 2,089 | 'Leaf emergence' | 'Fall color / leaf senescence' | 205 |
| Seattle / UW | 2,063 | 'Leaf emergence' | 'Fall color / leaf senescence' | 231 |
| Olympia / Tumwater | 2,025 | 'Leaf emergence' | 'Fall color / leaf senescence' | 269 |
| Tacoma / Puyallup | 1,993 | 'Leaf emergence' | 'Fall color / leaf senescence' | 301 |
| Bellingham / Whatcom | 1,972 | 'Leaf emergence' | 'Fall color / leaf senescence' | 322 |
| Sequim / Rain Shadow | 1,906 | 'Leaf emergence' | 'Fall color / leaf senescence' | 388 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'First bloom' BBCH '61' | 902 | '' |
| 'Flower buds visible' BBCH '51' | 902 | '' |
| 'Bud break' BBCH '07' | 1129 | '' |
| ● 'Leaf emergence' BBCH '11' NOW | 1417 | '' |
| ○ 'Fall color / leaf senescence' BBCH '93' NEXT | 2294 | '' est. May 22 (forecast) |
Sources: 'NPN citizen science observations (WA+OR), n=24, median. services.usanpn.org' ; observation Kent 2026-04-09' About GDD₃₂ →
Season tracker for Kent / Auburn as of May 13, 2026. Predicted dates use 16-day weather forecast through May 29, 2026, then climate normals.