Nippon Spirea
'Full bloom'Spiraea nipponica
Rosaceae · broadleaf deciduous shrub · introduced
Last updated
Nippon spirea is a deciduous shrub native to Japan, reaching 4-6 feet tall and wide with small, obovate leaves. The plant produces abundant white flowers in large, flat clusters along arching branches in late spring to early summer.
Nippon spirea is hardy to zones 4-8 and thrives in full sun to light shade with well-drained soil and moderate moisture. It is fast-growing and responds well to pruning immediately after flowering. The cultivar 'Snowmound' is more compact and is widely available.
Quick Facts
Spring Emergence / Primary Infection
Spring Colonization
Phenological Calendar
As of May 13, 2026, Puget Sound stations range from 1906.2 to 2098.2 GDD₃₂. Nippon Spirea has passed 'full bloom' (1815 GDD₃₂).
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 | 'Full bloom' | — | — |
| Kent / Auburn | 2,089 | 'Full bloom' | — | — |
| Seattle / UW | 2,063 | 'Full bloom' | — | — |
| Olympia / Tumwater | 2,025 | 'Full bloom' | — | — |
| Tacoma / Puyallup | 1,993 | 'Full bloom' | — | — |
| Bellingham / Whatcom | 1,972 | 'Full bloom' | — | — |
| Sequim / Rain Shadow | 1,906 | 'Full bloom' | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'First bloom' BBCH '61' | 1490 | '' |
| ● 'Full bloom' BBCH '65' NOW | 1815 | '' |
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.