Snowball viburnum is a flowering shrub that produces clusters of white blooms. These clusters, which can reach 8 inches (20 cm) in diameter, contribute to the plant’s name. Multiple balls of blooms begin to appear on the shrub in early spring and can continue to display throughout the summer months, depending on the variety. Once established, snowball viburnum shrubs are able to tolerate an array of conditions. For optimal blooms, viburnums require a minimum of six hours of sunlight. Pruning should be done after the blooms have fallen.
There are various types of snowball viburnum including the European, or Viburnum opulus ‘Roseum’; the Japanese, or Viburnum plicatum; and Chinese viburnum, or Viburnum macrocephalum. Viburnum opulus ‘Sterile’ is another European variety that is sometimes called the Eastern snowball and old-fashioned snowball bush. The ‘Roseum’ and ‘Sterile’ varieties are often referred to as the same type of snowball viburnum, but are distinct from one another, and the blooms on the ‘Roseum’ variety turn a faint shade of pink near the end of the season. There are other members included in the Viburnum genus, most of which have inherited the name “snowball bush.”
The European cranberry bush or Guelder-rose — Viburnum opulus — is highly popular throughout Europe and will produce red drupes toward the end of the summer months. The berries, which have low toxic levels, are acidic, but edible in small amounts when cooked, but should never be eaten raw. The name of the Guelder-rose, predominantly spelled gelder-rose in the United States, is derived from the Netherlands’ province of Guelderland. The shrubs were introduced into Colonial America during the latter part of the 18th century. The northeastern section of the United States, where it was introduced, is known for long, cold winters, conditions that the shrub is able to withstand, though in the 21st century, the snowball viburnum can be found in various regions throughout the world.
Viburnums are low-maintenance deciduous shrubs with small florets that emerge light green and then turn white. The balls of florets can last from several weeks to a couple of months, depending on the variety and climate. After the florets drop, the shrub continues to display its green foliage which will also drop when the weather turns cold. Caring for a snowball viburnum generally only requires regular pruning, and newly-planted viburnums should be placed in a well-draining location that allows space for the shrub to spread as it grows. They can reach large sizes, up to 20 feet (6 m) in height and nearly 15 feet (4.5 m) in width.
Although uncommon, several diseases may affect the snowball viburnum including powdery mildew and wood rot. The more encountered problem with the shrub is the Ceruraphis viburnicola, or snowball aphid. The aphids feed on the plant’s foliage causing deformity of the leaves.