Rosebay Rhododendron
Rhododendron maximum
Ericaceae · [VERIFY] · introduced
Last updated
A broadleaf evergreen shrub reaching 5 to 15 ft tall and 5 to 12 ft wide, native to eastern North America from Nova Scotia south to Georgia and west to Ohio, concentrated in the Appalachians. Known as the rosebay rhododendron, it is the most widely distributed native rhododendron in the eastern United States. Flowers are white to pale pink, often with greenish-yellow spotting.
Notable for exceptional shade tolerance; one of the few rhododendrons that performs well in deep shade. Growth rate is slow. All parts are poisonous to humans, cats, dogs, and horses.
Quick Facts
Phenological Calendar
As of May 24, 2026, Puget Sound stations range from 2172.5 to 2394 GDD₃₂. Rosebay Rhododendron typically reaches beginning of flowering at 2828 GDD₃₂, predicted around Jun 9.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of May 24, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,394 | Pre-season | Beginning of flowering | 434 |
| Kent / Auburn | 2,373 | Pre-season | Beginning of flowering | 455 |
| Seattle / UW | 2,332 | Pre-season | Beginning of flowering | 496 |
| Olympia / Tumwater | 2,295 | Pre-season | Beginning of flowering | 533 |
| Tacoma / Puyallup | 2,259 | Pre-season | Beginning of flowering | 569 |
| Bellingham / Whatcom | 2,256 | Pre-season | Beginning of flowering | 573 |
| Sequim / Rain Shadow | 2,173 | Pre-season | Beginning of flowering | 656 |
View full calendar (1 stages)
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ Beginning of flowering BBCH 61 NEXT | 2828 | — est. Jun 9 (forecast) |
Source: OSU phenology catalog (OSU: weather.cfaes.osu.edu) About GDD₃₂ →
Season tracker for Kent / Auburn as of May 24, 2026. Predicted dates use 16-day weather forecast through Jun 9, 2026, then climate normals.