White Ash
Fraxinus americana
Oleaceae · broadleaf deciduous tree · native
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
White ash (Fraxinus americana, Oleaceae) is a moderate-growing deciduous tree native to eastern North America from Nova Scotia to Minnesota and south to Florida and Texas, reaching 50 to 80 feet with a spread of about 49 feet. Opposite, pinnate compound leaves (20 to 38 centimeters) bear 5 to 9 leaflets (usually 7) that are dark green above with distinctive glaucous undersides. Fall color ranges from yellow to maroon to deep purple. Dioecious flowers lack petals and appear before leaves in April to May.
White ash grows in full sun on wet-tolerant soils (pH 4.7 to 7.5) with high water needs and low drought tolerance, hardy in Zones 4a to 8b. It reaches about 40 feet at 20 years. Documented diseases (8 total) include Nectria canker, anthracnose, and verticillium wilt. Pest associations (9 total) include ash borer, carpenterworm, and lecanium scale. The emerald ash borer, present in Oregon and devastating to all Fraxinus species, is the dominant threat. The cultivar 'Autumn Purple' (seedless male clone, deep purple-red fall color) is the primary selection.
Quick Facts
Phenological Calendar
As of April 23, 2026, Puget Sound stations range from 1434.4 to 1592.7 GDD₃₂. White Ash has reached bloom start (1102 GDD₃₂) and is approaching leaf emergence, predicted around Apr 25.
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 | Bloom start | Leaf emergence | 2 |
| Olympia / Tumwater | 1,505 | Bloom start | Leaf emergence | 35 |
| Bellingham / Whatcom | 1,483 | Bloom start | Leaf emergence | 56 |
| Tacoma / Puyallup | 1,472 | Bloom start | Leaf emergence | 67 |
| Sequim / Rain Shadow | 1,434 | Bloom start | Leaf emergence | 105 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ● Bloom start BBCH 61 NOW | 1102 | Apr 1-Apr 30 |
| Full bloom BBCH 65 | 1080 | — |
| Bud break BBCH 07 | — | Feb 15-Mar 15 |
| ○ Leaf emergence BBCH 11 NEXT | 1539 | Mar 1-Apr 1 est. Apr 25 (forecast) |
| Bloom end / petal fall BBCH 69 | — | Apr 15-May 15 |
| Fruit/seed development BBCH 71 | — | Jun 1-Aug 31 |
| Fruit/seed maturity BBCH 85 | — | Sep 1-Nov 30 |
| Fall color / leaf senescence BBCH 93 | — | Oct 1-Nov 15 |
| Dormancy BBCH 97 | — | Nov 15-Feb 28 |
GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? Source GDD₅₀ thresholds from Herms 2004 (OSU, Secrest Arboretum, Ohio) and UMD IPMnet (Gill & Klick, mid-Atlantic), converted to GDD₃₂ via Kent bloom-date mapping. Season tracker for Kent / Auburn as of Apr 23, 2026. Predicted dates use 16-day weather forecast through May 10, 2026, then climate normals.