Bottlebrush Buckeye
Aesculus parviflora
Sapindaceae, Hippocastanaceae · broadleaf deciduous shrub · native
Last updated
Data Coverage 4 of 6 dimensions
Quick Facts
Height
8–12 ft
Spread
13 ft
Growth Rate
Slow
Light
Full Sun to Shade
Soil
Moist
Water
Moderate
Hardiness
Zone Zones 4a–8b
Bloom Time
June to July
Origin
extends from South Carolina, Georgia to Alabama and Florida
Phenological Calendar
As of April 3, 2026, Puget Sound stations range from 1070 to 1180.6 GDD₃₂. Bottlebrush Buckeye typically reaches 'first bloom' at 3024 GDD₃₂, predicted around Jun 23.
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' | 1,843 |
| Seattle / UW | 1,171 | Pre-season | 'First bloom' | 1,853 |
| Kent / Auburn | 1,111 | Pre-season | 'First bloom' | 1,913 |
| Olympia / Tumwater | 1,106 | Pre-season | 'First bloom' | 1,918 |
| Bellingham / Whatcom | 1,101 | Pre-season | 'First bloom' | 1,923 |
| Tacoma / Puyallup | 1,075 | Pre-season | 'First bloom' | 1,949 |
| Sequim / Rain Shadow | 1,070 | Pre-season | 'First bloom' | 1,954 |
| Stage | GDD32 | Typical Window |
|---|---|---|
| ○ 'First bloom' BBCH '61' NEXT | 3024 | '' est. Jun 23 (avg) |
| 'Full bloom' BBCH '65' | 3330 | '' est. Jul 4 (avg) |
Range: 2515–2896 GDD₃₂
(6yr)
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.