By Sonoma County Master Gardener Barbara Kirbach
Viburnums are a genus of more than 150 evergreen, semi-evergreen and deciduous woody plants from the Adoxaceae family. They are native primarily to Northern temperate regions although some hail from Southeast Asia and South America. Many of the hardiest are native to North America and are best grown in USDA Zones 3-8, with some variance by species. The shrub is prevalent in Mediterranean areas but is not drought tolerant and will need adequate moisture during our hot, dry summers. I tend to have viburnums on my mind at this time of year, because their brilliant foliage is one of the highlights of the autumn landscape.
Viburnums are upright shrubs usually 6 to 10 feet in height with about a 4-foot spread. However, some varieties such as v. sieboldii can reach 20 feet or the height of a small tree. A few dwarf varieties such viburnum opulus ‘Nanum’ are less than 3 feet. The shrub’s leathery leaves, which are usually dark green on top and lighter in color underneath, are a perfect contrast to its creamy white to pink blossoms and dark red, blue or black berries. They can have either lacecap, domed or snowball-shaped clusters of flowers. Some varieties need a pollinator close by to produce a good showing of berries. The pollinator should be another viburnum of the same species, but a different variety.
Viburnums are not fussy. They can be grown in just about any location be it sun or part shade. However, sun is preferable for flower and seed production. Give them moderately fertile (about 1/3 organic material) and moist, well-drained soil with a
Some Favorite Varieties
Viburnum tinus (laurustinus) ‘Spring Bouquet’ is aptly named, as its blooms are most abundant in late winter and early spring. They begin as pale pink buds, which open into tight, 2 to 4 inch clusters of tiny, fragrant white flowers. Small lavender to deep purple berries accompany the flowers which bloom periodically throughout the year. It is this succession of buds, blooms and berries that is so attractive to birds, bees and butterflies. Thus, if the viburnums are threatened by an infestation of aphids, to which they are often prone, the birds can be of help in removing them. However, if all does not go accordingly to Nature’s plan, spray the pests with a strong stream of water or give them a dose of Neem oil. It also bears mentioning that this variety of viburnum is deer resistant.
Because of its dense foliage compared to other viburnums, laurustinus, as it is commonly called, makes an excellent hedge, foundation planting or even a single specimen. Four years ago, we needed a screen along one edge of our property, so we opted to plant six, gallon-sized viburnum tinus ‘Spring Bouquets’ about six feet apart from their centers. Following instructions from the California Growers’ Guide, we created a long watering basin two feet from the hedge line, built two parallel 6-inch high berms, mulched the surface with two inches of compost and kept them well-watered until established. We fed the shrubs in the spring and fall with a complete 15-15-15 fertilizer. Today, we have an informal, evergreen hedge standing about 8-feet tall. (Note: there are some varieties of ‘Spring Bouquets’ that are more compact.) Viburnums do not require regular pruning. However, it is wise to cut back vigorous shoots for preferred balance and shape in early to mid summer. Do not deadhead or the plant will not produce its charming berries.
To delineate another border in our garden, we wanted a viburnum that was showy, but not as profuse as the laurustinus. Thus, we installed six viburnum plicatum var. tomentosum ‘Summer Snowflakes’ or doublefile viburnums, with an approximate mature height and width of 8 x 6 feet. Their 1 ½ to 2- inch, lacecap clusters of white flowers are perched along the shrub’s horizontally tiered branches from June through September. Their berries age from red to black and their foliage changes from deep orange to burgundy red in autumn.
Other cultivars of doublefile v. plicatum var. tomentosum that are truly show-stoppers with their graceful, outstretched spread of horizontal branches include Viburnum plicatum ‘Mariesii’, a deciduous shrub with a moderate growth rate, green oval leaves that turn red in the fall and large flat-headed white flowers; ‘Kern’s Pink’, with its densely rounded shape, bronze- tinged oval leaves that turn dark red in fall and large pale pink, domed shaped blooms and ‘Shasta’, with its abundant, large, white, lacecap flowers, bright red fruit and maroon foliage in the fall. Many of these varieties can be found locally at Urban Tree Farm, Emerisa Gardens, Sonoma Mission Gardens and Digging Dog Nursery (located in Mendocino, but with an established mail-order business).
Like garden designer Ken Twombly, whenever I’ve needed a shrub for a problem area, be it dry, wet, sunny or shady, a viburnum has always come to my rescue.
References: Sunset Western Garden Book, Pruner’s Bible, California Grower’s Guide, Bay Area Gardening, Fine Gardening.
©Sonoma County Master Gardeners