Winterberrry Winterberry Holly

Ilex verticillata

Aquifoliaceae · broadleaf deciduous shrub · native

Last updated

Data Maturity Structured

This profile synthesizes data from multiple published sources. Expert field review is in progress.

Quick Facts

Height
10 ft
Spread
5 ft
Growth Rate
Moderate
Light
Sun to Part Shade
Soil
Wet Tolerant
Water
High
Hardiness
Zone Zones 3a–8b
Bloom Time
June to July
Origin
extends over much of eastern and central North America

Phenological Calendar

As of April 24, 2026, Puget Sound stations range from 1455.1 to 1613.4 GDD₃₂. Winterberrry Winterberry Holly typically reaches bloom start at 2700 GDD₃₂, predicted around Jun 10.

Regional Season Tracker

GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 24, 2026
Station GDD₃₂ Current Stage Next To Go
Issaquah / East King 1,613 Pre-season Bloom start 1,087
Seattle / UW 1,574 Pre-season Bloom start 1,126
Kent / Auburn 1,559 Pre-season Bloom start 1,141
Olympia / Tumwater 1,524 Pre-season Bloom start 1,177
Bellingham / Whatcom 1,504 Pre-season Bloom start 1,196
Tacoma / Puyallup 1,492 Pre-season Bloom start 1,208
Sequim / Rain Shadow 1,455 Pre-season Bloom start 1,245
Stage GDD32 Typical Window
Bloom start BBCH 61 NEXT 2700 May 1-May 31 est. Jun 10 (avg)
Full bloom BBCH 65 3050 est. Jun 23 (avg)
Bud break BBCH 07 Feb 15-Mar 15
Leaf emergence BBCH 11 Mar 1-Apr 1
Bloom end / petal fall BBCH 69 May 15-Jun 15
Fruit/seed development BBCH 71 Jun 1-Aug 31
Fruit/seed maturity BBCH 85 Sep 1-Nov 30
Fall color / leaf senescence BBCH 93 Oct 1-Nov 15
Dormancy BBCH 97 Nov 15-Feb 28
Range: 2128–2462 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 24, 2026. Predicted dates use 16-day weather forecast through May 10, 2026, then climate normals.

Diseases (8)

Pests (11)

Cultivars (3)

'Red Sprite'
Common name: Red Sprite Winterberry Red Sprite Winterberry Holly; Mature height: 3–5 ft
Hardy to USDA Zone 3
'Sunsplash'
Common name: Sunsplash Winterberry Sunsplash Winterberry Holly
Hardy to USDA Zone 3
'Winter Red'
Common name: Winter Red Winterberry Winter Red Winterberry Holly; Mature height: 8 ft
Hardy to USDA Zone 3