Over 150 types of viburnum exist. The choices range from deciduous and evergreen shrubs to small trees. Viburnums are native to North America and Asia. They grow 2 to 30 feet tall and produce white and pink flowers in clusters at the end of the branches. The foliage consists of glossy green to dull, dark green leaves that turn to red or purple in the autumn. Small berries are yellow, orange, red, pink, blue or black. With the proper care, viburnums will grow at least 2 feet per year.
Viburnums are fast growing plants that create quick hedges and privacy screens. They are also used as foundation and background shrubs in landscapes. They are showy and make an attractive single shrub showcased in your garden or front yard.
The ideal time to plant a viburnum is in the fall, but most varieties are ready for purchase from nurseries during the spring when they are beginning to bloom. Container grown viburnum shrubs will survive planting in the spring. Give spring planted viburnums extra water throughout the summer to counteract the heat.
Prepare your planting site in an area of full sun to partial shade. Pick a site that has moist, rich soil with a pH of 5.5 to 6.5. Mix 10 percent organic matter into the soil. For example, if your are planting your viburnum in 10 inches of soil spread 1 inch of peat moss over the soil. Dig and mix the organic material and soil together. Space your viburnum shrubs 4 to 10 feet apart.
Viburnums can tolerate some cold weather, but it is best to give it a little help to ensure winter survival. Spread 2 to 3 inches of bark mulch around the shrubs before the ground freezes in the fall. This will help keep the soil from drying out, will regulate the soil temperature and protect the roots from freezing.
Established viburnum shrubs are low maintenance bushes. During long dry spells during the summer, soak them deeply to ensure they have enough water. Remove old and weak branches to keep the shrubs healthy. Prune them in early spring to control the height and width of the viburnum.
Viburnum shrubs are susceptible to fungal leaf spots which are black, sunken scabs that appear on older leaves during warm, moist summer months. Algal leaf spot will attack viburnums during cool, moist conditions and produce small, pale green circles that change to reddish-brown as the spots age. Powdery mildew and downy mildew is also a problem with viburnums.
Most diseases that infect viburnums are prevented by keeping the leaves dry. Avoid overhead watering by applying water directly to the soil around the shrubs. Hand remove any infected leaves and rake up any fallen leaves. Destroy the infected foliage in order to reduce chances of infection of next year's leaves. Do not compost any leaves that may be infected by plant diseases.