Winterberrry Winterberry Holly

Ilex verticillata

Aquifoliaceae · broadleaf deciduous shrub · native

Last updated March 9, 2026

Data Coverage 5 of 6 dimensions

Site Data

Threats

Cultivars

Phenology

GDD Thresholds

Puget Sound

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 12, 2026, Puget Sound stations range from 1235.8 to 1375.3 GDD₃₂. Winterberrry Winterberry Holly typically reaches bloom start at 2700 GDD₃₂, predicted around Jun 12.

Regional Season Tracker

GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 12, 2026

Station	GDD₃₂	Current Stage	Next	To Go
Issaquah / East King	1,375	Pre-season	Bloom start	1,325
Seattle / UW	1,348	Pre-season	Bloom start	1,352
Kent / Auburn	1,308	Pre-season	Bloom start	1,392
Olympia / Tumwater	1,292	Pre-season	Bloom start	1,408
Bellingham / Whatcom	1,270	Pre-season	Bloom start	1,430
Tacoma / Puyallup	1,258	Pre-season	Bloom start	1,442
Sequim / Rain Shadow	1,236	Pre-season	Bloom start	1,464

Stage	GDD₃₂	Typical Window	What to Look For
○ Bloom start BBCH 61 NEXT	2700	May 1-May 31 est. Jun 12 (avg)	First open flowers visible; flowers white
Full bloom BBCH 65	3050	— est. Jun 24 (avg)	Crown in full flower; heavy pollinator activity
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 end / petal fall BBCH 69	—	May 15-Jun 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

Regional estimate

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 12, 2026. Predicted dates use 16-day weather forecast through Apr 28, 2026, then climate normals.

Diseases (9)

Several factors Red Leaf Spotting Phytophthora leaf & twig blight Green algae Green Algae Many commercial Boron Deficiency Symptom category — not a single disease Leaf Spot Phytophthora ilicis Phytophthora Leaf and Twig Blight Phytophthora spp. (P Phytophthora Root Rot Venturia inaequalis Scab Fumago vagans Sooty Mold

Pests (11)

Parthenolecanium spp. Lecanium scale Pulvinaria floccifera Cottony camellia scale Coccus hesperidum Brown soft scale Argyrotaenia franciscana Orange tortrix Phytomyza ilicis Holly leafminer Rhopobota naevana Holly bud moth Aphidoidea Aphid Leafroller (Orange tortrix) Otiorhynchus spp. Root weevil Tetranychidae Spider mite Tortricidae Leafroller

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