Carolina Silverbell Mountain Silverbell

Halesia carolina

Styracacaceae · broadleaf deciduous tree · introduced

Last updated March 9, 2026

Data Coverage 3 of 6 dimensions

Site Data

Threats

Cultivars

Phenology

GDD Thresholds

Puget Sound

Quick Facts

Height

30–40 ft

Spread

32 ft

Growth Rate

Moderate

Light

Part Shade

Soil

Wet Tolerant

Water

Moderate

Hardiness

Zone Zones 4a–8b

Bloom Time

April

Origin

the Appalachians Mountains of North Carolina to Tennessee

Phenological Calendar

Regional Season Tracker

GDD₃₂ accumulation across 7 Puget Sound stations · as of Mar 22, 2026

Station	GDD₃₂	Current Stage	Next	To Go
Seattle / UW	1,013	Bloom start	Full bloom	184
Issaquah / East King	1,006	Bloom start	Full bloom	191
Olympia / Tumwater	952	Pre-season	Bloom start	7
Bellingham / Whatcom	948	Pre-season	Bloom start	11
Kent / Auburn	942	Pre-season	Bloom start	17
Sequim / Rain Shadow	924	Pre-season	Bloom start	35
Tacoma / Puyallup	921	Pre-season	Bloom start	38

Stage	GDD₃₂	Typical Window	What to Look For
Bud break BBCH 07	—	Feb 15-Mar 15	Buds swelling and beginning to open; first green tissue visible
Leaf emergence BBCH 11	—	Mar 1-Apr 1	First leaves fully unfurled on new growth
○ Bloom start BBCH 61 NEXT	959	Apr 1-Apr 30 est. Mar 24 (forecast)	First open flowers visible; flowers white
Bloom end / petal fall BBCH 69	—	Apr 15-May 15	Last petals falling; flower structures fading
Fruit/seed development BBCH 71	—	Jun 1-Aug 31	Fruit or seed structures forming; fruit color: red
Fruit/seed maturity BBCH 85	—	Sep 1-Nov 30	Fruit fully colored and ripened; seed dispersal may begin
Fall color / leaf senescence BBCH 93	—	Oct 1-Nov 15	Leaves changing color; fall display beginning
Dormancy BBCH 97	—	Nov 15-Feb 28	Leafless; no active growth; dormant buds set
Full bloom BBCH 65	1197	— est. Apr 8 (avg)	Crown in full flower; heavy pollinator activity

Regional estimate

Range: 635–790 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 Mar 22, 2026. Predicted dates use 16-day weather forecast through Apr 7, 2026, then climate normals.