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
As of April 19, 2026, Puget Sound stations range from 1342.9 to 1500.8 GDD₃₂. Japanese Snowbell typically reaches 'first bloom' at 1932 GDD₃₂, predicted around May 9.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 19, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,501 | Pre-season | 'First bloom' | 431 |
| Seattle / UW | 1,465 | Pre-season | 'First bloom' | 467 |
| Kent / Auburn | 1,441 | Pre-season | 'First bloom' | 491 |
| Olympia / Tumwater | 1,415 | Pre-season | 'First bloom' | 517 |
| Bellingham / Whatcom | 1,390 | Pre-season | 'First bloom' | 542 |
| Tacoma / Puyallup | 1,381 | Pre-season | 'First bloom' | 552 |
| Sequim / Rain Shadow | 1,343 | Pre-season | 'First bloom' | 589 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Leaf emergence' BBCH '11' | — | 'Early April' |
| ○ 'First bloom' BBCH '61' NEXT | 1932 | '' est. May 9 (avg) |
| 'Full bloom' BBCH '65' | 2336 | '' est. May 26 (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 Apr 19, 2026. Predicted dates use 16-day weather forecast through May 5, 2026, then climate normals.