Identifying characteristics: This genus contains over 150 species, 15 of which are native to North America. Viburnums are upright, deciduous or evergreen shrubs or occasionally small trees. The leaves are opposite, simple and toothed or 3-lobed. Often wart-like glands occur on the leaf stalk just below the blade. Most species have small, white or occasionally pink flowers produced in tight, terminal clusters or flattened heads. Some produce large, sterile outer flowers along with the fertile, inconspicuous blooms. Different species may have either fragrant or unpleasant-smelling flowers. The fruit is a persistent drupe (similar to a tiny plum) produced in yellow, orange, pink, red, blue or black clusters. For good fruit crops, plants may be planted in groups to ensure cross-pollination. The fruit contains a single seed which is dispersed by birds.
Similar species:
- The 3-lobed varieties may be mistaken for maples (for example red maple, Acer rubrum) in the absence of fruit.
Ecology:
Distribution: Viburnums are native to the temperate regions of
Europe, Asia and North America and prefer moist, humus-rich, well-drained
soils.
Habitat: Most species grow well in sun or shade, but evergreen
species prefer some shade. Viburnums are sensitive to liquid sprays and
dusts containing sulfur, which are used to combat leaf diseases. Viburnums
are relatively free of major problems, although they may be attacked by
leafspot, crown gall, powdery mildew, aphid, thrips and twig borer.
Uses:
Wildlife: Most viburnums hold their fruit into the late fall
or winter months, making them important to birds and other wildlife. The
nannyberry (V. lentago), a small tree or tall shrub to 20 feet, is
especially attractive to wildlife. This species is native to Iowa, growing
in moist uplands and thickets. It has small, white flowers and is an excellent
plant for hedges and windbreaks. The blackhaw viburnum (V. prunifolium),
a native of the eastern US, is a large shrub or small tree commonly planted
in Iowa and on campus. The lustrous, bright green leaves turn reddish-purple
in the fall. It bears attractive white flowers in spring, followed by sweet,
edible, bluish-black fruits that may be used in preserves.
Horticulture: The arrowhead viburnum (V. dentatum) is a tough plant, withstands high pH, and is ideal for hedges, groupings or as a parking lot screen. Maple-leaved viburnums produce showy clusters of red fruit. Viburnums present the landscape designer with a variety of choices from specimens and tub plants, to border accents and screens.
