Showy Forsythia
Forsythia ×intermedia
Oleaceae · broadleaf deciduous shrub · introduced
Last updated
Showy forsythia (Forsythia × intermedia, Oleaceae) is a fast-growing deciduous shrub of hybrid origin (eastern Asian parentage), reaching 8 to 10 feet tall and 10 to 12 feet wide with upright, arching branches. Pale to deep yellow, four-lobed flowers (3 to 4 centimeters) cover the bare branches in early spring before leaves emerge. It is a key phenological indicator plant: bloom timing correlates with crabgrass pre-emergent application windows and pest emergence thresholds.
Showy forsythia grows in full sun on adaptable soils with moderate water needs, hardy in Zones 4a to 8b. It blooms on old wood; prune immediately after flowering. Documented diseases include bacterial blight, stem gall, and virus; root weevil is an occasional pest. OSU notes cultivars including 'Lynwood Gold,' 'Spectabilis,' and 'Spring Glory.'
Quick Facts
Field Observations
Phenological Calendar
As of May 18, 2026, Puget Sound stations range from 2022.7 to 2224.5 GDD₃₂. Showy Forsythia has passed 'full bloom' (686 GDD₃₂).
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of May 18, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 2,225 | 'Full bloom' | — | — |
| Kent / Auburn | 2,194 | 'Full bloom' | — | — |
| Seattle / UW | 2,164 | 'Full bloom' | — | — |
| Olympia / Tumwater | 2,128 | 'Full bloom' | — | — |
| Bellingham / Whatcom | 2,098 | 'Full bloom' | — | — |
| Tacoma / Puyallup | 2,092 | 'Full bloom' | — | — |
| Sequim / Rain Shadow | 2,023 | 'Full bloom' | — | — |
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'First bloom' BBCH '61' | 423 | '' |
| ● 'Full bloom' BBCH '65' NOW | 686 | '' |
Source: 'Master catalog (OSU, UMD), GDD50 base' About GDD₃₂ →
Season tracker for Kent / Auburn as of May 18, 2026. Predicted dates use 16-day weather forecast through Jun 3, 2026, then climate normals.