Lewis' Mock Orange
'Flower buds visible'Philadelphus lewisii
Hydrangeaceae · broadleaf deciduous shrub · native
Last updated
Philadelphus lewisii (Hydrangeaceae) is a deciduous shrub native to western North America from British Columbia to California and east to Montana. It grows 6 to 10 feet tall with arching branches. Clusters of pure white, four-petaled flowers (1 to 1.5 inches across) appear in late spring to early summer and are intensely fragrant. The species was named for Meriwether Lewis, who collected it during the Lewis and Clark expedition.
Lewis's mockorange grows in full sun to part shade on well-drained soil with moderate moisture. It tolerates dry conditions once established. It blooms on old wood, so pruning should follow flowering. The species is the state flower of Idaho. No significant pest or disease problems are documented. Hardy in Zones 4a to 8b.
Quick Facts
Spring Infection Period
Phenological Calendar
As of May 13, 2026, Puget Sound stations range from 1906.2 to 2098.2 GDD₃₂. Lewis' Mock Orange has reached 'flower buds visible' (1585 GDD₃₂) and is approaching 'first bloom', predicted around May 29.
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 | 'Flower buds visible' | 'First bloom' | 376 |
| Kent / Auburn | 2,089 | 'Flower buds visible' | 'First bloom' | 385 |
| Seattle / UW | 2,063 | 'Flower buds visible' | 'First bloom' | 411 |
| Olympia / Tumwater | 2,025 | 'Flower buds visible' | 'First bloom' | 449 |
| Tacoma / Puyallup | 1,993 | 'Flower buds visible' | 'First bloom' | 481 |
| Bellingham / Whatcom | 1,972 | 'Flower buds visible' | 'First bloom' | 502 |
| Sequim / Rain Shadow | 1,906 | 'Flower buds visible' | 'First bloom' | 568 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Bud break' BBCH '07' | 778 | '' |
| 'Leaf emergence' BBCH '11' | 983 | '' |
| ● 'Flower buds visible' BBCH '51' NOW | 1585 | '' |
| ○ 'First bloom' BBCH '61' NEXT | 2474 | '' est. May 29 (forecast) |
Source: 'NPN citizen science observations (WA+OR), n=39, median. services.usanpn.org' 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.