Cutleaf Red Alder
Alnus rubra f. pinnatisecta
Betulaceae · broadleaf deciduous tree · native
Last updated
This cutleaf form of red alder features deeply lobed leaves resembling delicate oak foliage, offering textural interest beyond the species' solid contribution to pioneer recovery. Like the straight species, it colonizes disturbed ground rapidly, reaching 90 feet at maturity and achieving 50 feet in just 20 years. Native to the Pacific coast from Alaska to California.
Red alder's greatest gift is nitrogen fixation through symbiotic root nodules that enrich impoverished soils, making it invaluable for erosion control and forest restoration. Plant it on wet ground, along streambanks, or in disturbed areas where its explosive growth accelerates recovery. Expect a short lifespan (60 to 80 years maximum) and watch for root rot, collar rot, and canker diseases; this tree is a temporary but essential component of forest succession, not a permanent specimen tree.
Quick Facts
Phenological Calendar
As of April 3, 2026, Puget Sound stations range from 1070 to 1180.6 GDD₃₂. Cutleaf Red Alder has reached 'leaf emergence' (1049 GDD₃₂) and is approaching 'fall color / leaf senescence', predicted around May 18.
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 | 'Leaf emergence' | 'Fall color / leaf senescence' | 882 |
| Seattle / UW | 1,171 | 'Leaf emergence' | 'Fall color / leaf senescence' | 892 |
| Kent / Auburn | 1,111 | 'Leaf emergence' | 'Fall color / leaf senescence' | 952 |
| Olympia / Tumwater | 1,106 | 'Leaf emergence' | 'Fall color / leaf senescence' | 957 |
| Bellingham / Whatcom | 1,101 | 'Leaf emergence' | 'Fall color / leaf senescence' | 962 |
| Tacoma / Puyallup | 1,075 | 'Leaf emergence' | 'Fall color / leaf senescence' | 988 |
| Sequim / Rain Shadow | 1,070 | 'Leaf emergence' | 'Fall color / leaf senescence' | 993 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'First bloom' BBCH '61' | 844 | '' |
| 'Bud break' BBCH '07' | 854 | '' |
| 'Full bloom' BBCH '65' | 886 | '' |
| 'Flower buds visible' BBCH '51' | 1031 | '' |
| ● 'Leaf emergence' BBCH '11' NOW | 1049 | '' |
| ○ 'Fall color / leaf senescence' BBCH '93' NEXT | 2063 | '' est. May 18 (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.