There is no cure for boxwood blight, but by tweaking planting and growing techniques and choosing varieties that tend to be more resistant to the disease, boxwood is still a very viable option for many. And many believe it’s worth a little extra effort to save this popular workhorse. “Even with all the issues that are being thrown at it, I still love boxwood. It’s such an elegant plant,” says Andrea Filippone, a partner at F2 Environmental Design and president of the American Boxwood Society.
American boxwood (Buxus sempervirens) and English boxwood (Buxus sempervirens “Suffruticosa”), a more compact version with aromatic foliage, dominate the market. The nicknames are confusing because they aren’t native to America or England. Both plants, which are hardy to Zone 5, actually originated in southern Europe, western Asia and North Africa.
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English boxwood is particularly popular because it can be tightly clipped and used to delineate spaces, screen unwanted views, create privacy, sculpt forms and more. Unfortunately, English boxwood is also most susceptible to boxwood blight, and experts say that planting it is asking for trouble. Other susceptible cultivars include Elegantissima, Vardar Valley, Morris Dwarf and Justin Brouwers. Instead, consider planting cultivars that have proved semi-resistant, such as the dwarf Little Missy and variegated Golden Dream.
Regardless of the variety you choose, Filippone says adjusting your growing techniques can also help make your boxwood less vulnerable to disease. Filippone is trained as an architect, and when she initially designed her 26-acre New Jersey property in 1994 she turned to boxwood to form wall-like hedges and create garden “rooms.” In 2006, she traveled to the Balkans and Caucasus Mountains to see boxwood in its native habitat, and it was an eye opener.
“Boxwood tolerates extreme heat and cold. They grow in crags of limestone with sparse water, lean nutrients, and well-drained soil,” she says. Her takeaway: “We baby this plant too much. We give it too much water and too much fertilizer.” She says boxwood would be happier and healthier if we grew it lean and mean, so even before blight arrived in the United States, she began employing organic methods to provide healthy soil teeming with microorganisms. Now she advocates using these methods to help prevent the disease.
In addition to using organic soil, she says, it’s important to provide good drainage for boxwood’s shallow roots. “Add sand to the soil or create wicks (such as drainage pipes) to channel water away,” Filippone says. It may be necessary to water your boxwood when you plant it, but after it is established, it should only be watered in a drought, and only with a watering can or drip irrigation. Never water it with overhead irrigation systems, which can allow excess water to accumulate on the leaves.
Also choose your site carefully. Boxwood can grow in shade, but dappled light or filtered sun will dry the leaves more rapidly after it rains. Saunders points out that the disease often becomes prevalent in autumn, when the days get shorter and the shrubs stay wet longer, which creates ideal conditions for blight. Planting in a bright location with good air circulation helps dry the foliage.
Altering pruning habits is another key tactic. Boxwood is often clipped into dense, tight shapes. Instead, trim it with an eye toward allowing air to flow throughout the plant. “Prune a boxwood so you see dappled light through the foliage at the base to encourage air circulation,” Filippone says. The best time to prune is February through March.
Also, to promote air flow, avoid fully wrapping boxwood in burlap for winter protection. Instead, mulch it with shredded bark no deeper than an inch to discourage splash-up from fallen disease spores. And be careful to disinfect tools, boots and gloves after working with a plant to prevent the transmission of the disease.
Saunders also suggested diversifying plantings as a preventive measure, coupling boxwoods with other shrubs. Because the blight specifically targets members of the boxwood family, mixing them with other plants will help reduce the risk of spreading the contagion. But avoid growing it with the related pachysandra and sweetbox (Sarcococca sp.), which can host the disease.
You can also, of course, look for alternatives to boxwood, but finding a shrub with similar traits is a tall order. The most common option is the Japanese holly (Ilex crenata), which has small leaves and a tight growth habit that can be trained to mimic boxwood, making it a virtual look-alike. The native inkberry (Ilex glabra) is another alternative. But Tim Kane, inventory and marketing manager at Prides Corner Farms in Lebanon, Conn., points out that boxwood is king for a reason. “Boxwood got where it is by offering the suite of traits that gardeners need,” he says.
At the top of that list of traits is that boxwood is typically resistant to deer, unlike Japanese holly and inkberry. Ilex plants aren’t a good option in places where deer are a severe issue. That is one of many reasons Andrea Filippone urges gardeners to keep boxwood in their toolbox. “Boxwood is still a beautiful and useful plant, we just need to help it fight off problems,” she says.
Tovah Martin is a gardener and freelance writer in Connecticut. Find her online at tovahmartin.com.