Boxwoods: A Virginia Staple
Boxwoods have fascinated me ever since childhood when I discovered a hiding place inside two 15 foot tall specimens of American boxwood in my grandmother’s garden. Since they are emblematic of traditional Virginia yards, you can imagine my distress to discover that the English boxwoods we planted eight years ago were not all thriving like those giants. Here’s what my wife and I discovered about these old standbys of landscaping.
Varieties: Although hundreds of cultivars exist, three main groups do well with care in central Virginia: Littleleaf (sometimes called Japanese), Common and Korean boxwoods. Thankfully, deer usually avoid them all.
Littleleaf (Buxus microphylla) is compact, hardy, heat and pollution tolerant, but may require pruning to keep a perfect shape.
Common (Buxus sempervirens) includes the familiar American as well as English boxwood. Because there are many choices in color and size, choose your cultivar carefully. Note: We dug our English boxwoods from a friend’s yard and have had to replace several with hardier varieties.
Korean (Buxus sinica. var. insularis) also varies from 2-7 feet tall and as much as 10 feet wide, depending on the cultivar and can come with light green foliage.
Culture: This is where I needed help. Boxwoods need fertile, well-drained soil regularly amended with organic matter. Because their roots are shallow, soil under the drip line can only be scraped lightly and should be covered with a single inch of aged mulch spread 12 inches beyond the drip line. The best site includes partial sun year round and some protection from harsh winter winds. They will benefit from thinning in the fall (which I had failed to do) to permit better air circulation. Follow pruning by shaking the plant gently to remove dead leaves and then cleaning them up to protect against disease. This is especially true for English boxwoods (B. sempervirens ‘Suffruticosa’) which seem more susceptible to insects and disease. Fresh mulch can be added to keep down grass and weeds.
When a soil test indicates nutrients are needed, broadcast granular fertilizer with a 10-6-4 analysis on top of the mulch just beyond the drip line in the fall. Because roots are shallow, it’s important to let the fertilizer dissolve and soak through to the soil. Too much fertilizer will cause browning. A soil test through the Extension Service will indicate if amendments are necessary. Nitrogen deficiency shows up when lower leaves exhibit a uniform yellowing, especially older leaves inside the plant.
Just because their leaves don’t wilt, we shouldn’t forget that boxwoods can suffer from summer drought and winter winds so water as needed. You can protect plants from especially severe winters and heavy snowfall by wrapping them in burlap.
Thinning, pruning and shearing: We often choose boxwoods for landscaping for a couple of very good reasons: they keep their color and can be shaped nicely either by selecting the right cultivar or by shearing. However, bear in mind these hints. Early winter is the time for major pruning to reduce size. Severe reductions in size should be spread over two years. Reach inside the shrub about 6-8 inches down with sharp bypass pruners and cut back to a major joint. Remove about 10 percent of the outer branches. English boxwoods tend to grow especially dense and thus are susceptible to disease, so thinning to promote air circulation is important. In early June, we can shear plants to the shape desired. Since this shaping does not promote the best growth, the plant can then be pruned lightly, taking off only 1-2” branches to encourage more light and air. Again, shake and rake because litter accumulation leads to adventitious roots which can be damaged by excessive heat and cold.
Despite their hardiness, boxwoods do get diseases and pests. The best defense is good cultural practices and quick identification of problems with help from Virginia Cooperative Extension. Boxwood blight has been identified not far from Piedmont Virginia. Insure that new plants come disease-free from reputable dealers.
“Selecting Landscape Plants: Boxwoods” Va. Coop.Ext., ext.vt.edu/426/426-603
The Boxwood Handbook (Lynn R. Batdorf)
“Thin Boxwoods for Improved Plant Health,” U.S. National Arboretum website, http://www.usna.usda.gov/Gardens/faqs/BoxwoodThinning.html
“About Boxwood,” boxwoodsociety.org
“Best Management Practices for Boxwood Blight in the Virginia Home Landscape,” Va.Coop.Ext. pubs.ext.vt.edu/PPWS-29/pdf