Japanese Tree Lilac
Near 'First 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.
Quick Facts
Spring Infection Period
Crawler Emergence
Spring Emergence / Primary Infection
Adult Emergence & Foliar Feeding
Phenological Calendar
As of May 13, 2026, Puget Sound stations range from 1906.2 to 2098.2 GDD₃₂. Japanese Tree Lilac typically reaches 'first bloom' at 2167 GDD₃₂, predicted around May 17.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of May 13, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,098 | Pre-season | 'First bloom' | 69 |
| Kent / Auburn | 2,089 | Pre-season | 'First bloom' | 78 |
| Seattle / UW | 2,063 | Pre-season | 'First bloom' | 104 |
| Olympia / Tumwater | 2,025 | Pre-season | 'First bloom' | 142 |
| Tacoma / Puyallup | 1,993 | Pre-season | 'First bloom' | 174 |
| Bellingham / Whatcom | 1,972 | Pre-season | 'First bloom' | 195 |
| Sequim / Rain Shadow | 1,906 | Pre-season | 'First bloom' | 261 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ 'First bloom' BBCH '61' NEXT | 2167 | '' est. May 17 (forecast) |
| 'Full bloom' BBCH '65' | 2573 | '' est. Jun 2 (avg) |
Source: 'Master catalog (OSU), converted GDD50->GDD32 via Kent bloom-date mapping' About GDD₃₂ →
Season tracker for Kent / Auburn as of May 13, 2026. Predicted dates use 16-day weather forecast through May 29, 2026, then climate normals.