American Hazel
Corylus americana
Betulaceae · broadleaf deciduous shrub · native
Last updated
Data Maturity Structured
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Quick Facts
Height
8–15 ft
Growth Rate
Moderate
Light
Sun to Part Shade
Soil
Moist
Water
Moderate
Hardiness
Zone Zones 4a–8b
Bloom Time
March to April
Origin
from Newfoundland to Saskatchewan and south to eastern
Phenological Calendar
As of April 23, 2026, Puget Sound stations range from 1434.4 to 1592.7 GDD₃₂. American Hazel has passed 'leaf emergence' (886 GDD₃₂).
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 | 'Leaf emergence' | — | — |
| Olympia / Tumwater | 1,505 | 'Leaf emergence' | — | — |
| Bellingham / Whatcom | 1,483 | 'Leaf emergence' | — | — |
| Tacoma / Puyallup | 1,472 | 'Leaf emergence' | — | — |
| Sequim / Rain Shadow | 1,434 | 'Leaf emergence' | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Full bloom' BBCH '65' | 394 | '' |
| 'First bloom' BBCH '61' | 461 | '' |
| 'Bud break' BBCH '07' | 879 | '' |
| ● 'Leaf emergence' BBCH '11' NOW | 886 | '' |
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 23, 2026. Predicted dates use 16-day weather forecast through May 10, 2026, then climate normals.
Diseases (19)
Multiple obligate biotrophic fungi (Erysiphales: Erysipha... Powdery Mildew Anisogramma anomala Eastern Filbert Blight Pseudomonas syringae pv. syringae Bacterial Blight Armillaria ostoyae Armillaria Root Rot [VERIFY] Blanks Cryptosporella umbrina Brown Stain Symptom category — not a single disease Canker Catkin Blast Candidatus Phytoplasma pyri Decline/Collapse Syndrome Fungal agents (multiple) Kernel Molds Symptom category — not a single disease Leaf Spot Apple mosaic virus (ApMV) Mosaic Mosses and Lichens Fumago vagans Sooty Mold Daffodil yellow stripe virus (DYVV) Stunt (Dilly) Sunburn Wet Feet Taphrina wiesneri Witches' Broom Limb and Wood Decay
Pests (9)
Malacosoma spp. Tent caterpillar Cnephasia longana Omnivorous leaftier Parthenolecanium spp. Lecanium scale Cydia latiferreana Filbertworm Archips rosanus Filbert Leafroller Phytoptus avellanae Filbert Bud Mite Myzocallis coryli Filbert Aphid Phenacoccus aceris Apple Mealybug Halyomorpha halys Brown marmorated stink bug