Red Horsechestnut
Aesculus x carnea
Sapindaceae · [VERIFY] · introduced
Last updated
Hybrid horsechestnut reaching 35 to 50 feet tall with glossy, palmately compound foliage and showy pink to red flower spikes that appear in mid to late spring. Distinctive large candles of blossoms precede round, warty brown fruit.
Moderate maintenance ornamental shade tree preferring full sun and well-drained soil. Susceptible to Japanese beetle and scale insects. Excellent specimen tree for large landscapes; early leaf scorch can occur in hot, dry seasons.
Quick Facts
Phenological Calendar
As of April 19, 2026, Puget Sound stations range from 1342.9 to 1500.8 GDD₃₂. Red Horsechestnut typically reaches beginning of flowering at 1562 GDD₃₂, predicted around Apr 25.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 19, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,501 | Pre-season | Beginning of flowering | 61 |
| Seattle / UW | 1,465 | Pre-season | Beginning of flowering | 97 |
| Kent / Auburn | 1,441 | Pre-season | Beginning of flowering | 121 |
| Olympia / Tumwater | 1,415 | Pre-season | Beginning of flowering | 147 |
| Bellingham / Whatcom | 1,390 | Pre-season | Beginning of flowering | 172 |
| Tacoma / Puyallup | 1,381 | Pre-season | Beginning of flowering | 182 |
| Sequim / Rain Shadow | 1,343 | Pre-season | Beginning of flowering | 219 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ Beginning of flowering BBCH 61 NEXT | 1562 | — est. Apr 25 (forecast) |
| Full bloom BBCH 65 | 1809 | — est. May 4 (forecast) |
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 Apr 19, 2026. Predicted dates use 16-day weather forecast through May 5, 2026, then climate normals.