Cutleaf Red Alder
'Fall color / leaf senescence'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
Spore Release (Fall & Spring Rains)
Aecial Stage (Alternate Host)
Larval Feeding
Active Below-ground Growth
+ 4 more — see full disease and pest lists below
Phenological Calendar
As of May 13, 2026, Puget Sound stations range from 1906.2 to 2098.2 GDD₃₂. Cutleaf Red Alder has passed 'fall color / leaf senescence' (2063 GDD₃₂).
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 | 'Fall color / leaf senescence' | — | — |
| Kent / Auburn | 2,089 | 'Fall color / leaf senescence' | — | — |
| Seattle / UW | 2,063 | 'Leaf emergence' | 'Fall color / leaf senescence' | 0 |
| Olympia / Tumwater | 2,025 | 'Leaf emergence' | 'Fall color / leaf senescence' | 38 |
| Tacoma / Puyallup | 1,993 | 'Leaf emergence' | 'Fall color / leaf senescence' | 70 |
| Bellingham / Whatcom | 1,972 | 'Leaf emergence' | 'Fall color / leaf senescence' | 91 |
| Sequim / Rain Shadow | 1,906 | 'Leaf emergence' | 'Fall color / leaf senescence' | 157 |
| 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' | 1049 | '' |
| ● 'Fall color / leaf senescence' BBCH '93' NOW | 2063 | '' |
Source: 'NPN citizen science observations (WA+OR), n=106, median. services.usanpn.org' 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.