Winterberrry Winterberry Holly

Near Bloom start

Ilex verticillata

Aquifoliaceae · broadleaf deciduous shrub · introduced

Last updated May 11, 2026

Plant Profile

Size & Form

Height

10 ft

Spread

5 ft

Growth Rate

Moderate

Size at 20 yr

6 ft

Lifespan

Moderate

Site Requirements

Light

Sun to Part Shade

Soil Drainage

Wet Tolerant

Soil pH

4.5-7.5

Water

High

Drought Tolerance

Low

Hardiness

Zones 3a–8b

Ornamental Interest

Bloom Time

June to July

Fall Color

Yellow

Origin

extends over much of eastern and central North America

AphidHigh

Peak Population & Dispersal

Phytophthora Root RotModerate

Growing Season Stress Expression

Sooty MoldModerate

Heavy Mold Colonization

Holly leafminerModerate

Adult Emergence & Egg Laying

+ 2 more — see full disease and pest lists below

Diseases: Regionally Documented (8)

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 spp. (P Phytophthora Root Rot Venturia spp. — multiple host-specific species: V Scab Fumago vagans Sooty Mold

Pests: Regionally Documented (10)

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 Otiorhynchus spp. Root weevil Tetranychidae Spider mite Tortricidae Leafroller

Phenological Calendar

As of June 3, 2026, Puget Sound stations range from 2435.5 to 2672.8 GDD₃₂. Winterberrry Winterberry Holly typically reaches bloom start at 2700 GDD₃₂, predicted around Jun 5.

Regional Season Tracker

GDD₃₂ accumulation across 7 Puget Sound stations · as of Jun 3, 2026

Station	GDD₃₂	Current Stage	Next	To Go
Issaquah / East King	2,673	Pre-season	Bloom start	27
Kent / Auburn	2,665	Pre-season	Bloom start	35
Seattle / UW	2,610	Pre-season	Bloom start	90
Olympia / Tumwater	2,570	Pre-season	Bloom start	131
Tacoma / Puyallup	2,535	Pre-season	Bloom start	165
Bellingham / Whatcom	2,533	Pre-season	Bloom start	167
Sequim / Rain Shadow	2,436	Pre-season	Bloom start	265

View full calendar (9 stages)

Stage	GDD₃₂	Typical Window	What to Look For
○ Bloom start BBCH 61 NEXT	2700	May 1-May 31 est. Jun 5 (forecast)	First open flowers visible; flowers white
Full bloom BBCH 65	3050	— est. Jun 18 (forecast)	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)

Sources: USDA Plants Database (seasonal estimate) ; OSU phenology catalog (OSU: weather.cfaes.osu.edu) About GDD₃₂ →

Season tracker for Kent / Auburn as of Jun 3, 2026. Predicted dates use 16-day weather forecast through Jun 19, 2026, then climate normals.

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

Data Maturity

Structured Multiple sources. Expert review underway.