Northern Lights Forsythia
Forsythia x intermedia
Oleaceae · [VERIFY] · introduced
Last updated
Deciduous shrub growing 6 to 8 feet tall with bright yellow four-lobed flowers covering arching stems in early spring before leaf emergence. Foliage is medium green; form is loose and spreading.
Hardy, low-maintenance spring accent shrub thriving in full sun to light shade and adaptable soils. Prune after flowering to shape; old canes can be removed at the base. No significant pests or diseases; tends toward leggy growth without selective pruning.
Quick Facts
Phenological Calendar
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Mar 30, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,116 | Full bloom | — | — |
| Seattle / UW | 1,112 | Full bloom | — | — |
| Olympia / Tumwater | 1,049 | Full bloom | — | — |
| Kent / Auburn | 1,048 | Full bloom | — | — |
| Bellingham / Whatcom | 1,041 | Full bloom | — | — |
| Tacoma / Puyallup | 1,017 | Full bloom | — | — |
| Sequim / Rain Shadow | 1,012 | Full bloom | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| Beginning of flowering BBCH 61 | 423 | — |
| ● Full bloom BBCH 65 NOW | 686 | — |
GDD = Growing Degree Days (base 32°F, Jan 1 start). Why base 32? Source GDD₅₀ thresholds from Herms 2004 (OSU, Secrest Arboretum, Ohio) and UMD IPMnet (Gill & Klick, mid-Atlantic), converted to GDD₃₂ via Kent bloom-date mapping. Season tracker for Kent / Auburn as of Mar 30, 2026. Predicted dates use 16-day weather forecast through Apr 15, 2026, then climate normals.