Japanese Stewartia
Stewartia pseudocamellia
Theaceae · broadleaf deciduous tree · introduced
Last updated
Japanese stewartia is a deciduous tree native to Japan, reaching 30-50 feet tall with exfoliating, mottled gray and tan bark. The tree produces white flowers with crinkled petals and orange stamens in midsummer and oblong leaves that turn striking purple-red to orange in fall.
Japanese stewartia thrives in partial shade to full sun with well-drained, acidic, humus-rich soil and consistent moisture. Hardy to zones 5-8, it is slow to medium in growth rate with exceptional ornamental value from flowers, fall foliage, and winter bark. The tree does not tolerate drought stress.
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 | 1,971 |
| Seattle / UW | 1,112 | Pre-season | Beginning of flowering | 1,975 |
| Olympia / Tumwater | 1,049 | Pre-season | Beginning of flowering | 2,039 |
| Kent / Auburn | 1,048 | Pre-season | Beginning of flowering | 2,039 |
| Bellingham / Whatcom | 1,041 | Pre-season | Beginning of flowering | 2,046 |
| Tacoma / Puyallup | 1,017 | Pre-season | Beginning of flowering | 2,070 |
| Sequim / Rain Shadow | 1,012 | Pre-season | Beginning of flowering | 2,075 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ Beginning of flowering BBCH 61 NEXT | 3087 | — est. Jun 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 Mar 30, 2026. Predicted dates use 16-day weather forecast through Apr 15, 2026, then climate normals.