Boxwoods are supposed to be green, 24/7, 365 days a year. So it's no wonder that when boxwoods turn brown, people get upset and demand answers. Why is this awful thing happening?????? As always, Grumpy knows.
The Two Main Culprits Absent a hobo who lives in your bushes and regularly relieves himself on their foliage, the probable cause of brown boxwoods is one of two soil-borne diseases -- Phytophthora root rot or English boxwood decline. The first attacks American boxwood (Buxus sempervirens), English boxwood (B. sempervirens 'Suffruticosa'), and littleleaf boxwood (B. microphylla). The latter attacks English boxwood. Above ground, the damage from either looks like this.
Healthy, deep green leaves first turn light green, then brown or yellowish, then straw-colored. Whole branches die and the foliage drops.
Dig up the afflicted plant and you'll see why the leaves turned brown. Most of the roots have rotted away. Boxwoods can't grow without roots.
What Can I Spray to Cure My Boxwoods? Both diseases are present in the soil, so spraying won't help. Infected boxwoods are going to croak -- it's as simple as that. Some fungicides exist that you can drench the soil with to possibly protect your healthy boxwoods, but only professionals have access to them, so forget that. And while some new selections of English boxwood are said to be resistant to boxwood decline, unless you belong to the American Boxwood Society (a lively group), you'll likely never see one.
So How Can I Prevent These Diseases? Healthy plants seldom get sick. Stressed plants do. It makes sense, therefore, to give boxwoods the proper growing conditions to keep them happy.
Boxwoods like full sun or light shade. Most important, they like loose, moist, fertile soil that drains quickly. Plant them in heavy, clay soil that stays wet and you might as well dip them in lava. So don't plant in low spots where water pools after a rain or at the foot of a downspout. That invites Phytophthora root rot. And water them deeply during summer droughts. Drought stress promotes English boxwood decline. Don't wet the foliage when you water. Splashing water can spread disease.
Can I Replace My Dead Boxwood With Another Boxwood? Sure. But since these two diseases live in the soil, your new boxwood will probably die of them too. Then you'll get really peeved. So plant something else.
More Info on Boxwoods For additional reading on using and caring for boxwoods, check out these articles:
- "Boxwood Basics"
- "Boxwoods for Every Landscape"
- "Transplanting Boxwood Step-By-Step"
- "Boxwoods: Perfect For Pots"