Silk Tree
Albizia julibrissin
Fabaceae · broadleaf deciduous tree · introduced
Last updated
Data Coverage 4 of 6 dimensions
Quick Facts
Height
20–30 ft
Spread
32 ft
Growth Rate
Fast
Light
Full Sun
Soil
Wet Tolerant
Water
Moderate
Hardiness
Zone Zones 6a–8b
Bloom Time
June to July
Origin
from Iran to central China
Phenological Calendar
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Mar 22, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Seattle / UW | 1,013 | Pre-season | Bloom start | 2,389 |
| Issaquah / East King | 1,006 | Pre-season | Bloom start | 2,396 |
| Olympia / Tumwater | 952 | Pre-season | Bloom start | 2,450 |
| Bellingham / Whatcom | 948 | Pre-season | Bloom start | 2,454 |
| Kent / Auburn | 942 | Pre-season | Bloom start | 2,460 |
| Sequim / Rain Shadow | 924 | Pre-season | Bloom start | 2,478 |
| Tacoma / Puyallup | 921 | Pre-season | Bloom start | 2,481 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| Bud break BBCH 07 | — | Feb 15-Mar 15 |
| Leaf emergence BBCH 11 | — | Mar 1-Apr 1 |
| ○ Bloom start BBCH 61 NEXT | 3402 | Jul 1-Jul 31 est. Jul 7 (avg) |
| Full bloom BBCH 65 | 3724 | — est. Jul 17 (avg) |
| Bloom end / petal fall BBCH 69 | — | Jul 15-Aug 15 |
| Fruit/seed development BBCH 71 | — | Jun 1-Aug 31 |
| Fruit/seed maturity BBCH 85 | — | Sep 1-Nov 30 |
| Leaf drop BBCH 93 | — | Oct 15-Nov 30 |
| Dormancy BBCH 97 | — | Nov 15-Feb 28 |
Range: 2711–3098 GDD₃₂
(6yr)
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 Mar 22, 2026. Predicted dates use 16-day weather forecast through Apr 7, 2026, then climate normals.
Cultivars (1)
'Summer Chocolate' Summer Chocolate®
Common name: Summer Chocolate Silk Tree; Mature height: 20 ft
Hardy to USDA Zone 6