Viburnum tested for W.Pa. gardens
Viburnum is one of my favorite ornamental shrubs. It has it all: sweet smelling spring flowers, beautiful fall foliage, and berries that add late summer and fall interest as well as provide food for fall migrating birds.
Viburnums also are tough and able to handle the weather extremes and clay soil of our area.
Over the past few years, I've experimented with growing several varieties of viburnum and have come up with a list of the best-performing viburnum.
To make this list, the plant had to be winter hardy for zone 5 gardens, drought tolerant, mildew resistant and preferably resistant to the viburnum leaf beetle Pyrrhalta viburni.
My favorite is V. plicatum rosacea, sometimes called Japanese Snowball. This viburnum blooms from the first part of May until the end of June. The blossoms are both pink and white and cover the plant.
The foliage is dark green and deeply engraved. I purchased this plant in a one-gallon pot four years ago at a local nursery; it has tripled in size and bloomed every year since it was planted.
Next on my list is Summer Snowflake, V. plicatum tomentosum. Summer Snowflake has a moderate growth rate, is deer resistant and has colorful fall foliage. Its best features are the beautiful flowers that resemble snowflakes, and the long bloom time from late spring through summer.
One of my newer viburnums is a witherod viburnum, V. nudum “Brandywine,” sometimes called Possumhaw. This shrub is planted in an open area without protection from wind or weather and has done quite well. The leaves of this plant are smooth and very glossy. The blooms, while not quite as showy as those of other viburnums, are large and will turn into a cluster of blue, purple and pink fruits that the birds love.
Another favorite witherod viburnum is V. nudum “Winterthur.” The plant is very hardy, grows moderately fast, and is one of the first viburnums to leaf out in spring. The flowers are white and quite showy followed by beautiful deep blue berries and colorful red foliage in fall.
I also have grown Blue Muffin viburnum, V. dentatum. While this plant is a fast grower, strong bloomer and attractive to birds and butterflies, the Blue Muffin viburnum is susceptible to damage from the viburnum leaf beetle.
The only viburnum in my yard that did not make the list is my Guelder Rose viburnum, V. opulus. The attractive maplelike shaped leaves are unique and the flowers range from white to a beautiful light pink, but the plants were devastated by the viburnum beetle. Even with multiple treatments, the plants did not recover. I do not recommend this plant.The viburnum leaf beetle can kill susceptible viburnum plants if infestations are not managed. Female leaf beetles start laying eggs on leaves and twigs from early summer into fall. The eggs overwinter on the plant and the larvae emerge in late April or early May when temperatures rise. These larvae, if not stopped, eat the viburnum leaves between the veins and can skeletonize an entire shrub.In early summer, the larvae crawl down the shrub into the soil and pupate. Several weeks later, the adult beetles emerge from the soil and once again start feeding on the viburnum leaves. They feed, mate and lay eggs until they are killed off by frost in the fall.Treatment of the viburnum leaf beetle depends upon their life-cycle stage. From fall through early spring, check for egg-infested branches and twigs, and prune them out. Evidence of eggs appears as rows of small bumps on the underside of young branches. The bumps are not the actual eggs, but rather covered pockets created by the egg-laying beetle as she deposits her eggs. Pruning out eggs sites is the most effective method of controlling the viburnum leaf beetle infestation.If your viburnum has been skeletonized by the larvae, it is possible to treat it with a pesticide spray. Insecticides work best on the larvae rather than the adult beetles. Beneficial insects such as the lady beetle larvae and adults, as well as the spined soldier bug and lacewing larvae will feed on the viburnum beetle, so before spraying an insecticide, check to see if they are present. To protect pollinators, wait until the plant has finished flowering or remove the blossoms before spraying.I treated the infestation on my Blue Muffin viburnum with an organic insect spray that contains pyrethrins. I also removed as many beetles as possible with the garden hose and pruned branches that had a large number of beetles on them. This plant has recovered but will need to be treated yearly.A healthy plant is more likely to survive beetle damage. Keep your plants watered in times of drought, and apply a slow-release fertilizer before new growth begins in spring. While a light pruning can be performed throughout the year as necessary to shape or remove dead or damaged branches, any major pruning should be done in late winter or early spring.If you have questions about growing viburnums or control of the viburnum leaf beetle, contact the Master Gardener Greenline at 724-287-4761, Ext. 229.
