Whether used for long, sweeping formal hedges or as intricately sculpted specimens, boxwoods (Buxus spp.) are valuable evergreens for the home landscape. These fine-textured shrubs are long-lived and adaptable, but unfortunately are susceptible to winter damage from drying winds and road salt.
Boxwoods and Street Salt
Boxwoods have a low tolerance to salt spray and should be planted away from roadways that are treated with salt in winter. Keep in mind that the salt used on icy roads becomes airborne at high vehicular speeds and can affect plants 100 to 150 feet from the roadway. On roads with low-speed vehicle traffic, salt damage occurs when the ice melts and water runoff carries the salt into landscape soil near the road.
Recognizing Salt Damage
Road salt damages boxwoods in two ways. Airborne salt spray burns leaf tissues, causing browning starting at the tips and moving toward the base of the leaves as spring progresses. New buds and twigs may also be damaged. Salt injury is usually seen only on the side of the plant facing the road. With runoff, water contaminated with road salt inhibits the boxwood's ability to absorb water and nutrients, leading to progressive plant decline.
Boxwoods weakened by winter damage are susceptible to leaf spot disease caused by the fungus Macrophoma candollei. Symptoms of this disease include yellow leaves spotted with small, black fungal spores. Consult your local extension service or garden center for a fungicide suitable for boxwoods in your area. Both direct salt spray and salt-laden road runoff make boxwoods susceptible to this disease.
You can protect boxwoods from salt injury in several ways. Place barriers such as snow fences or burlap around plants to block salt spray. These barriers also help prevent damage from drying winter winds. Don't shovel snow from areas treated with salt onto boxwoods' root zones. If you know plants have been exposed to winter salt runoff, flush the soil around the plants' roots to dilute the salt. And in your own landscape, use a salt alternative such as calcium magnesium or calcium chloride, available as deicer pellets made from limestone and acetic acid, or abrasive materials such as sand or ash.
- Penn State; Boxwoods for Pennsylvania Landscapes; James Sellmer, et al.; 2008
- University of Illinois Extension: Korean Boxwood
- Purdue University Extension; Salt Damage in Landscape Plants; Janna Beckerman, et al.; April 2009
- The Ohio State University Extension; Salt Injury In The Landscape; Pam Bennett, et al.; April 1996
- University of Wisconsin Extension; Salt Injury to Landscape Plants; K. A. Delahaut, et al.; 1999
- Photo Credit Medioimages/Photodisc/Photodisc/Getty Images
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