What's Killing My Boxwood?

Boxwoods are supposed to be green all year, so it's no wonder that people get upset when boxwoods turn brown. Why is this awful thing happening? As always, Grumpy knows.

The Two Main Culprits

The probable cause of brown boxwoods is one of two soil-borne diseases—Phytophthora root rot or English boxwood decline. The first soil-borne disease attacks the American boxwood (Buxus sempervirens), English boxwood (B. sempervirens 'Suffruticosa'), and littleleaf boxwood (B. microphylla). The latter disease attacks the English boxwood. Above ground, the damage from either looks like this.

Healthy, deep green leaves turn light green, 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 only grow with roots.

What Can I Spray to Cure My Boxwoods?

When both diseases are present in the soil, spraying won't help. Infected boxwoods will die when these diseases are present—it's as simple as that. Some fungicides exist that you can drench the soil with to protect your healthy boxwoods, but only professionals can access them, so this isn't a probable solution. And while some new selections of English boxwood are said to be resistant to boxwood decline, unless you belong to the American Boxwood Society, 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 thrive in full sun or light shade. Most importantly, 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 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, so plant something else.

For additional reading on using and caring for boxwoods, explore boxwoods for every landscape or boxwoods for pots.

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