Japanese Snowbell
Styrax japonicus
Styracaceae · broadleaf deciduous tree · introduced
Last updated
Japanese snowbell is a deciduous tree native to Japan, reaching 20-30 feet tall with a pyramidal form and smooth gray bark. The tree produces white, slightly fragrant bell-shaped flowers hanging from branch undersides in early summer and opposite, ovate leaves with fine fall color.
Japanese snowbell thrives in partial shade to full sun with well-drained, slightly acidic to neutral soil and moderate moisture. Hardy to zones 5-8, it is slow to medium in growth. The distinctive downward-facing flowers are a major ornamental asset, and the plant is excellent for specimen plantings. It requires consistent moisture and does not tolerate drought.
Quick Facts
Phenological Calendar
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Mar 30, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,116 | Pre-season | Beginning of flowering | 697 |
| Seattle / UW | 1,112 | Pre-season | Beginning of flowering | 701 |
| Olympia / Tumwater | 1,049 | Pre-season | Beginning of flowering | 765 |
| Kent / Auburn | 1,048 | Pre-season | Beginning of flowering | 765 |
| Bellingham / Whatcom | 1,041 | Pre-season | Beginning of flowering | 772 |
| Tacoma / Puyallup | 1,017 | Pre-season | Beginning of flowering | 796 |
| Sequim / Rain Shadow | 1,012 | Pre-season | Beginning of flowering | 801 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ Beginning of flowering BBCH 61 NEXT | 1813 | — est. May 8 (avg) |
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 30, 2026. Predicted dates use 16-day weather forecast through Apr 15, 2026, then climate normals.