Japanese Tree Lilac
'Full bloom'Syringa reticulata
Oleaceae · broadleaf deciduous tree · introduced
Last updated
Japanese tree lilac, also called giant tree lilac, is a deciduous tree native to Japan, reaching 30-50 feet tall with a single stem or multi-stemmed form. The tree produces white, slightly fragrant flowers in large, pyramidal panicles in early to midsummer and has glossy, dark green leaves with fine bronze-red fall color.
Japanese tree lilac is hardy to zones 3-7 and thrives in full sun to light shade with well-drained soil. It blooms later than common lilac (June-July) and is less susceptible to mildew and scale. The tree is long-lived and low-maintenance once established; multiple cultivars are available.
Plant Profile
Size & Form
Site Requirements
Ornamental Interest
Active Conidial Spread
Crawler Emergence
Adult Emergence & Foliar Feeding
Diseases: Regionally Documented (7)
Pests: Regionally Documented (4)
Phenological Calendar
As of June 3, 2026, Puget Sound stations range from 2435.5 to 2672.8 GDD₃₂. Japanese Tree Lilac has passed 'full bloom' (2573 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Jun 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,673 | 'Full bloom' | — | — |
| Kent / Auburn | 2,665 | 'Full bloom' | — | — |
| Seattle / UW | 2,610 | 'Full bloom' | — | — |
| Olympia / Tumwater | 2,570 | 'First bloom' | 'Full bloom' | 4 |
| Tacoma / Puyallup | 2,535 | 'First bloom' | 'Full bloom' | 38 |
| Bellingham / Whatcom | 2,533 | 'First bloom' | 'Full bloom' | 40 |
| Sequim / Rain Shadow | 2,436 | 'First bloom' | 'Full bloom' | 138 |
View full calendar (2 stages)
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'First bloom' BBCH '61' | 2167 | '' |
| ● 'Full bloom' BBCH '65' NOW | 2573 | '' |
Source: 'Master catalog (OSU), converted GDD50->GDD32 via Kent bloom-date mapping' About GDD₃₂ →
Season tracker for Kent / Auburn as of Jun 3, 2026. Predicted dates use 16-day weather forecast through Jun 19, 2026, then climate normals.