The most ornamental feature of the winterberry holly (Ilex verticillata) centres on the plump and numerous berries that cling onto the leafless branches in fall and winter. All hollies are either male or female, based on the flower structure; only female shrubs produce fruits, and only if their late springtime flowers get pollinated. Grow winterberry holly across U.S. Department of Agriculture hardiness zones 4b through 8.
Nurseries grow and sell many varieties of winterberry shrubs. Match a female shrub with a male shrub that blooms at roughly the same time in spring. Bees are the primary pollinator of hollies, so with both male and female winterberry shrubs blooming at the same time, you increase the chances the insect carries pollen as it visits blossoms. Typically, winterberry shrubs are either early-, mid-, or late-season bloomers.
Two of the most common male winterberry cultivars grown and sold in North America are Jim Dandy and Southern Gentleman. Jim Dandy blooms in early-season and, therefore, pollinates early-flowering female selections, such as Red Sprite/Nana, Afterglow and Aurantiaca, according to the University of Connecticut. Late-flowering female shrubs, including Winter Red, Winter Gold or Cacapon, need the male Southern Gentleman winterberry shrub nearby. Hybrid winterberries (the result of crossing winterberry with fine-tooth holly, Ilex serrata) also involve male cultivars. Male hybrid shrubs include Apollo, and make good pollinators for female cultivars Sparkleberry or Winter Red. Raritan Chief, also a male shrub, blooms over a long time frame and pollinates a wide array of early-, mid- and late-season female winterberry shrubs.
Because male-flowering winterberry shrubs do not yield any fruits, they have little ornamental value; so relegate them to a background location in the garden. Plant the male shrub in the back of the planting bed or nestled in the centre of a cluster of female plants that mask and overshadow the mundane male plant in fall and winter. For the best chance of pollination, site male plants no more than 50 to 100 feet away from the female winterberry shrubs.
How Many Male Shrubs Do I Need?
One healthy male winterberry shrub produces enough flowers and pollen to effectively pollinate one to five nearby female winterberry plants according to Learn2Grow. If the female shrubs grow in separate parts of the landscape, 150 or more feet apart, plan on one male shrub in each distant cluster of up to five female plants. Both distance and number of female shrubs determines how many male shrubs to plant in the landscape.