Red Flowering Horsechestnut
Aesculus carnea
Sapindaceae, Hippocastanaceae · broadleaf deciduous tree · introduced
Last updated
Data Coverage 4 of 6 dimensions
Quick Facts
Height
35–50 ft
Light
Full Sun to Shade
Hardiness
Zone Zones 4–5
Phenological Calendar
As of April 3, 2026, Puget Sound stations range from 1070 to 1180.6 GDD₃₂. Red Flowering Horsechestnut typically reaches 'first bloom' at 1368 GDD₃₂, predicted around Apr 16.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 3, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,181 | Pre-season | 'First bloom' | 187 |
| Seattle / UW | 1,171 | Pre-season | 'First bloom' | 197 |
| Kent / Auburn | 1,111 | Pre-season | 'First bloom' | 257 |
| Olympia / Tumwater | 1,106 | Pre-season | 'First bloom' | 262 |
| Bellingham / Whatcom | 1,101 | Pre-season | 'First bloom' | 267 |
| Tacoma / Puyallup | 1,075 | Pre-season | 'First bloom' | 293 |
| Sequim / Rain Shadow | 1,070 | Pre-season | 'First bloom' | 298 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ 'First bloom' BBCH '61' NEXT | 1368 | '' est. Apr 16 (forecast) |
| 'Full bloom' BBCH '65' | 1672 | '' est. May 2 (avg) |
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 3, 2026. Predicted dates use 16-day weather forecast through Apr 19, 2026, then climate normals.
Cultivars (1)
'Oneill Red'
Common name: O'Neill Red Horsechestnut O'Neil Horsechestnut; Mature height: 35 ft