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.
Plant Profile
Size & Form
Site Requirements
Ornamental Interest
Active Conidial Spread
Peak Population & Dispersal
Diseases: Regionally Documented (2)
Pests: Regionally Documented (3)
Phenological Calendar
As of June 3, 2026, Puget Sound stations range from 2435.5 to 2672.8 GDD₃₂. Nippon Spirea has passed 'full bloom' (1815 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 | 'Full bloom' | — | — |
| Tacoma / Puyallup | 2,535 | 'Full bloom' | — | — |
| Bellingham / Whatcom | 2,533 | 'Full bloom' | — | — |
| Sequim / Rain Shadow | 2,436 | 'Full bloom' | — | — |
View full calendar (2 stages)
| 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 Jun 3, 2026. Predicted dates use 16-day weather forecast through Jun 19, 2026, then climate normals.