Speckled Alder
'Full bloom'Alnus incana subsp. rugosa
Betulaceae · broadleaf deciduous shrub · native
Last updated
Plant Profile
Size & Form
Height
20 ft
Growth Rate
Fast
Size at 20 yr
20 ft
Lifespan
Moderate
Site Requirements
Light
Sun to Part Shade
Soil Drainage
Wet Tolerant
Soil pH
5.5-7.0
Water
High
Drought Tolerance
Low
Hardiness
Zones 2a–8b
Ornamental Interest
Bloom Time
March
Origin
is eastern North America, it is most common in the Great
Watch for this season
Powdery MildewHigh
Active Conidial Spread
RustHigh
Uredinial Stage (Summer)
AphidHigh
Peak Population & Dispersal
Fall webwormHigh
Larval Feeding & Web Building
+ 3 more — see full disease and pest lists below
Diseases: Regionally Documented (11)
Armillaria spp. — primarily A Armillaria Root Rot Brown Leaf Blotch [VERIFY] Canker and Stem Diseases Viral agents Catkin Hypertrophy and Leaf Curl Collar Rot Lonsdalea quercina subsp Drippy Dieback Symptom category — not a single disease Leaf Spot Neonectria ditissima Nectria Canker Phytophthora spp. (P Phytophthora Root Rot Multiple obligate biotrophic fungi (Erysiphales: Erysipha... Powdery Mildew Multiple genera (Melampsoridium, Thekopsora, Naohidemyces... Rust
Pests: Regionally Documented (7)
Phenological Calendar
As of June 3, 2026, Puget Sound stations range from 2435.5 to 2672.8 GDD₃₂. Speckled Alder has passed 'full bloom' (1863 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Jun 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,673 | 'Full bloom' | — | — |
| Kent / Auburn | 2,665 | 'Full bloom' | — | — |
| Seattle / UW | 2,610 | 'Full bloom' | — | — |
| Olympia / Tumwater | 2,570 | 'Full bloom' | — | — |
| Tacoma / Puyallup | 2,535 | 'Full bloom' | — | — |
| Bellingham / Whatcom | 2,533 | 'Full bloom' | — | — |
| Sequim / Rain Shadow | 2,436 | 'Full bloom' | — | — |
View full calendar (5 stages)
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Bud break' BBCH '07' | 1353 | '' |
| 'Leaf emergence' BBCH '11' | 1353 | '' |
| 'First bloom' BBCH '61' | 1863 | '' |
| 'Flower buds visible' BBCH '51' | 1863 | '' |
| ● 'Full bloom' BBCH '65' NOW | 1863 | '' |
Source: 'NPN citizen science observations (WA+OR), n=36, median. services.usanpn.org' About GDD₃₂ →
Season tracker for Kent / Auburn as of Jun 3, 2026. Predicted dates use 16-day weather forecast through Jun 19, 2026, then climate normals.
Data Maturity Structured Multiple sources. Expert review underway.