The term “snowball tree” is a popular, non-botanical name used to describe several species of large shrubs or small trees recognized for their spectacular, globe-shaped flower clusters. This common name is derived from the appearance of the blossoms, which resemble dense, white spheres of snow. These ornamental plants are highly valued in landscaping for their abundant, showy flowers that appear in spring or summer, though they belong to different genera and have distinct growth habits and care requirements.
The Primary Varieties Known as “Snowball Tree”
The plants most frequently referred to as a snowball tree fall into two main groups: the Viburnum and the Hydrangea genera. One classic example is the European Snowball (Viburnum opulus ‘Roseum’), which is typically a large, deciduous shrub or small tree. This variety is notable for its late spring bloom time, providing a burst of white color early in the growing season. Another variety, the Chinese Snowball (Viburnum macrocephalum), can grow much taller, reaching up to 25 feet, and produces some of the largest flower heads among the Viburnums.
A separate group includes certain cultivars of Hydrangea, such as Hydrangea arborescens ‘Annabelle’. Unlike the Viburnums, ‘Annabelle’ is a much smaller deciduous shrub, typically reaching heights of three to five feet. This plant blooms later, starting in late spring or early summer and often continuing its display into the fall. The distinction between these two groups is important because it determines when and how they should be pruned.
Distinctive Physical Traits
The shared feature that unites these plants under the “snowball” name is the morphology of their inflorescences, or flower clusters. These clusters are dense, rounded, and pom-pom-like, composed entirely of sterile florets that give them their impressive, full shape. The blooms on both the Viburnum and Hydrangea varieties generally begin as a soft lime green color before maturing into pure, brilliant white. As the flowers age, some cultivars, particularly Viburnum opulus ‘Roseum’, may acquire a subtle blush of pink before they fade.
Beyond the flowers, the foliage and overall size offer clear differences. Viburnum opulus ‘Roseum’ features three-lobed leaves that resemble those of a maple tree and can provide attractive fall color in shades of orange and red. By contrast, Hydrangea arborescens ‘Annabelle’ displays broader, egg-shaped, dark green leaves that are sharply toothed. While the European Snowball Viburnum can reach twelve feet tall, the ‘Annabelle’ Hydrangea remains a compact shrub of four to five feet.
Cultivation and Maintenance Guidelines
Successful growth of a snowball tree depends on providing conditions that suit its specific genus, though both prefer moist, well-drained soil. Most varieties thrive when planted in a location that receives full sun to part shade, though afternoon shade is recommended in warmer climates to prevent stress. Hydrangea arborescens ‘Annabelle’ is particularly intolerant of drought conditions, requiring consistently moist soil throughout the growing season. Applying a layer of mulch helps to conserve soil moisture and regulate ground temperature.
Pruning Requirements
Pruning requirements differ significantly based on whether the plant blooms on old wood or new wood. Viburnum opulus ‘Roseum’ flowers on growth from the previous year, meaning pruning for shaping or size control must be done immediately after the spring flowering period. Pruning later in the year would remove the buds for the following season. Conversely, ‘Annabelle’ Hydrangea blooms on new wood grown in the current season, allowing for aggressive pruning in late winter or early spring before new growth emerges.
Pest and Support Issues
Regular maintenance should include monitoring for common issues specific to the variety. Viburnum varieties can be susceptible to pests such as aphids and the viburnum leaf beetle. For ‘Annabelle’ Hydrangea, the immense size of the flowers, which can reach up to twelve inches across, often causes the stems to bend and droop, especially after heavy rain. This requires planting in a protected area or providing support for the large flower heads.