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Winterberry Holly, Black Alder 'Skipjack'

Ilex verticillata

Family: Aquifoliaceae (a-kwee-foh-lee-AY-see-ee) (Info)
Genus: Ilex (EYE-leks) (Info)
Species: verticillata (ver-ti-si-LAH-tuh) (Info)
Cultivar: Skipjack
Hybridized by William N. Kuhl, McLean Nurseries
Registered or introduced: 2006



Foliage Color:

Unknown - Tell us

Bloom Characteristics:

This plant is attractive to bees, butterflies and/or birds

Water Requirements:

Average Water Needs; Water regularly; do not overwater

Requires consistently moist soil; do not let dry out between waterings

Very high moisture needs; suitable for bogs and water gardens

Where to Grow:

Unknown - Tell us


4-6 ft. (1.2-1.8 m)

6-8 ft. (1.8-2.4 m)

8-10 ft. (2.4-3 m)

10-12 ft. (3-3.6 m)


4-6 ft. (1.2-1.8 m)

6-8 ft. (1.8-2.4 m)

8-10 ft. (2.4-3 m)


USDA Zone 3a: to -39.9 C (-40 F)

USDA Zone 3b: to -37.2 C (-35 F)

USDA Zone 4a: to -34.4 C (-30 F)

USDA Zone 4b: to -31.6 C (-25 F)

USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

USDA Zone 9b: to -3.8 C (25 F)

Sun Exposure:

Full Sun

Sun to Partial Shade

Light Shade



Bloom Color:

White/Near White

Bloom Time:

Late Spring/Early Summer




Other details:

Unknown - Tell us

Soil pH requirements:

4.6 to 5.0 (highly acidic)

5.1 to 5.5 (strongly acidic)

5.6 to 6.0 (acidic)

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

Patent Information:


Propagation Methods:

From softwood cuttings

From semi-hardwood cuttings

By simple layering

Seed Collecting:

N/A: plant does not set seed, flowers are sterile, or plants will not come true from seed


This plant has been said to grow in the following regions:

Georgetown, Kentucky

Parkville, Maryland

Gardeners' Notes:


On Jan 25, 2012, ViburnumValley from Scott County, KY (Zone 5b) wrote:

'Skipjack' Winterberry Holly is a male plant necessary for pollination of all the wonderful fruiting female plants that have overlapping bloom time. These include the earlier blooming group of female clones like 'Afterglow', 'Aurantiaca', 'Chrysocarpa', 'Red Sprite', and 'Stoplight' among many others. This early and heavy blooming plant was selected and introduced by Bill Kuhl, the extraordinary nurseryman and holly enthusiast from the Baltimore MD area.

One can determine the sex of a Winterberry Holly when it is in bloom (if it is not known whether the plant fruits or not) by examining the small flowers. If the flowers have projecting stamens, it is a male plant. If the flowers only have a rounded bump in the center, then it is a female plant.

'Skipjack' r... read more