Scotch Broom
Cytisus scoparius
Fabaceae · broadleaf deciduous shrub · introduced
Last updated
Quick Facts
Height
4–8 ft
Spread
4–8 ft
Growth Rate
Fast
Light
Full Sun
Soil
Moist
Water
Moderate
Hardiness
Zones 5–6
Bloom Time
May to June
Origin
central and southern Europe
Phenological Calendar
As of May 24, 2026, Puget Sound stations range from 2172.5 to 2394 GDD₃₂. Scotch Broom has passed 'first bloom' (1539 GDD₃₂).
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 | 'First bloom' | — | — |
| Kent / Auburn | 2,373 | 'First bloom' | — | — |
| Seattle / UW | 2,332 | 'First bloom' | — | — |
| Olympia / Tumwater | 2,295 | 'First bloom' | — | — |
| Tacoma / Puyallup | 2,259 | 'First bloom' | — | — |
| Bellingham / Whatcom | 2,256 | 'First bloom' | — | — |
| Sequim / Rain Shadow | 2,173 | 'First bloom' | — | — |
View full calendar (5 stages)
| Stage | GDD32 | Typical Window |
|---|---|---|
| 'Fall color / leaf senescence' BBCH '93' | 1018 | '' |
| 'Bud break' BBCH '07' | 1084 | '' |
| 'Flower buds visible' BBCH '51' | 1304 | '' |
| 'Leaf emergence' BBCH '11' | 1337 | '' |
| ● 'First bloom' BBCH '61' NOW | 1539 | '' |
Range: 1177–1952 GDD₃₂
(8yr) · 36 obs
Source: 'NPN citizen science observations (WA+OR), n=10, median. services.usanpn.org' 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.
Cultivars (1)
'Moonlight'
Common name: Moonlight Scotch Broom
Data Maturity Baseline Extension data. Expert review underway.