Japanese Tree Lilac
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
Phenological Calendar
As of April 12, 2026, Puget Sound stations range from 1235.8 to 1375.3 GDD₃₂. Japanese Tree Lilac typically reaches 'first bloom' at 2167 GDD₃₂, predicted around May 22.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 12, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,375 | Pre-season | 'First bloom' | 792 |
| Seattle / UW | 1,348 | Pre-season | 'First bloom' | 819 |
| Kent / Auburn | 1,308 | Pre-season | 'First bloom' | 859 |
| Olympia / Tumwater | 1,292 | Pre-season | 'First bloom' | 875 |
| Bellingham / Whatcom | 1,270 | Pre-season | 'First bloom' | 897 |
| Tacoma / Puyallup | 1,258 | Pre-season | 'First bloom' | 909 |
| Sequim / Rain Shadow | 1,236 | Pre-season | 'First bloom' | 931 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ 'First bloom' BBCH '61' NEXT | 2167 | '' est. May 22 (avg) |
| 'Full bloom' BBCH '65' | 2573 | '' est. Jun 7 (avg) |
GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? Hover over GDD values for source details. Season tracker for Kent / Auburn as of Apr 12, 2026. Predicted dates use 16-day weather forecast through Apr 28, 2026, then climate normals.