Viburnum is a genus of about 150–175 species of shrubs or small trees in the moschatel family, Adoxaceae. The leaves are opposite, simple, and entire, toothed or lobed; cool temperate species are deciduous, while most of the warm temperate species are evergreen.
Some species are densely hairy on the shoots and leaves, with star-shaped hairs. Viburnum shrubs are one of the many ornamental shrubs that blooms on old wood, so waiting until after blooming to prune is recommended.
Trimming them during dormancy will result in the loss of all or many of the flower-producing buds. At the end of each bloom season, it’s a good idea to give your viburnum a quick clip to encourage new growth and thin out the interior, removing any old canes that are no longer producing leaves.
The Koreanspice viburnum, Viburnum carlesii, offers a glorious, sweet and fresh scent in late April from its pinkish and whitish flowers.
The City Garden in our Kemper Demonstration Gardens contains several shrubs of the species, while the April-blooming cultivar ‘Compactum,’ at just 2 ½ to 4 feet tall and wide, can be found in the Fragrance Garden, the Rhododendron Garden and the Woodland Garden. Let your nose follow the heavenly scent.
The fragrant snowball, Viburnum x carlcephalum, yields striking mounds of snow-white flowers that look as if they could be plucked off the bush and thrown at someone. This medium-tall viburnum can be found blooming in the Woodland Garden in mid- to late April.
Some viburnums provide visual interest to the winter garden, whether through evergreen leaves or colorful fruit drupes.
The hybrid lantanaphyllum, Viburnum x rhytidophylloides ‘Alleghany’ (a cross between V. rhytidophyllum and V. lantana ‘Mohican’), is an evergreen shrub that blooms in April, sometimes producing flowers on and off through the summer, and can be found in the Carver Garden in beds 2 and 3.
Another evergreen that is winter hardy in our area is the Prague viburnum, Viburnum ‘Pragense’, which also blooms in late April and can be found along the main trail in the Woodland Garden.
The arrowwood viburnum, Viburnum dentatum, is among the hardiest viburnums. This species can be found blooming during the second week of May or showing its nice red fall color in the Bird Garden and the Woodland Garden.
The nannyberry, Viburnum lentago, is a tall shrub, up to 16 feet, that blooms the last week of April through the first week of May and can be found in the Kemper Bird Garden.
The blackhaw, Viburnum prunifolium, uniquely places it flowers up above its leaves (while the flowers on many viburnums are nestled); you can see this species in the Bird Garden and Woodland Garden.
Our last Missouri native is the rusty blackhaw viburnum, Viburnum rufidulum, named for the rust-colored hairs on the leaf undersides and the stems.