Unsurpassed for bringing winter visual interest to the garden with bright red berries, common winterberry or black alder (Ilex verticillata) looks particularly attractive after a snowfall. The tiny flowers go unnoticed in spring, but the fruits ripen by autumn and become a food source for songbirds in early winter. Grow this deciduous shrub in USDA Hardiness Zones 4 through 9.
Common winterberry's native range extends across southeastern North America. It grows in moist soils along streams and lakes from Canada's Nova Scotia westward to the American states of Minnesota, Missouri and Texas, and eastward to the Florida Panhandle and Atlantic Ocean.
Growing as a multi-stemmed, upright shrub, it attains a mature height of 6 to 10 feet and equal width. The small oval leaves are leathery and light to medium green, blushing yellow and purple in autumn. The tiny white flowers hide under the foliage, but once pollinated by bees, develop into small round berries that ripen bright red in late summer. After the foliage turns yellow and fully drops away in mid-autumn, these berries highlight the beauty of the species, lining the gray-brown twigs. The fruits persist into mid- or late winter depending on severity of cold and appetites of birds.
All holly species (Ilex) are dioecious, a term to describe plants that are fully male or female in gender, based on their flowers. Common winterberry requires the presence of both gendered plants in the landscape to ensure female plants produce fruits each year. One male plant's flowers supplies enough pollen to fertilize three to seven nearby female plants' flowers, especially if within a distance of 50 to 100 feet.
Grow common winterberry in full or partial sun exposures, where it receives no less than 6 hours of direct sunlight daily. It prospers in a moist acidic soil with lots of organic matter incorporated. In the garden setting, any fertile, non-alkaline soil with good drainage suffices, although it will tolerate soggy soil spots. Both male and female plants must grow in proximity to ensure berries form on females.
Common winterberry becomes a large shrub, which is unsurpassed for use in a mixed shrub border or woodland garden. It may be grown as a singular specimen or in an informal cluster where male plants grow surreptitiously among the berry-producing female plants. People wishing to attract wildlife, especially songbirds, to their property find winterberry a "must-have" plant, as do those wishing to add visual excitement to landscapes during fall and winter months. Florists cut sprigs of the berry-lined branches in winter for embellishing Christmas wreaths, garlands and swags.
Several cultivated varieties, or cultivars, exist for use by gardeners, each with varying mature size, specific berry color, or gender. Male-flowering selections include 'Southern Gentleman' and 'Jim Dandy'. Only female cultivars bear fruits. A few producing red fruits are 'Cacapon', 'Winter Red', 'Red Sprite' and 'Sunsplash'. Orange to orange-red fruits develop on 'Shaver' and 'Afterglow'. Yellow berries grow on 'Winter Gold' and 'Chrysocarpa,' while more golden-orange berries occur on 'Aurantiaca'.