A healthy, green boxwood looks about as dignified as a plant can be. It adds an air of formality and permanence to the landscape, taking center stage in winter when trees are leafless and then receding gracefully into the background in summer when flowers dominate. Its tidiness and ease of maintenance make it a favorite just about everywhere it grows. But if yours appears more sickly than stately, one or more of the following factors may be to blame.
- Poor drainage--Boxwoods can't take standing water and heavy, wet soil. Poor drainage leads to root rot, which in turn causes parts of the shrub to become light brown and die. You can prune out the dead stuff, but unless you improve the drainage by redirecting excess water or amending the soil with lots of organic matter, the whole plant will eventually croak.
- Fungus--When a boxwood is sheared to produce denser outer foliage, dead leaves and stems can accumulate, unseen, in the center of the plant. This creates an incubator for fungal diseases that can cause potentially fatal dieback. To stop this, prune back all dying branches to healthy wood (as indicated by the green cambium layer just under the bark). Remove all debris from the center of the plant, and thin out some of the outside growth so that air and light can reach the center.
- Fluffy and Fido--When scent-marking pets pass by your plants, yellow and brown leaves soon follow. Repeated dousing can kill entire branches. Applying a product such as Lambert Kay Boundary or De-Fence Dog and Cat Repellent will discourage return visits.
- Exposure--Boxwoods thrive in full sun or light shade, but they don't like exposed, very windy sites, particularly in winter. They're generally cold hardy everywhere in the South. But if you live in the Upper South, seek out an especially hardy selection, such as 'Winter Gem,' 'Wintergreen,' 'Green Beauty,' 'Green Mountain,' or 'Green Velvet.' As a bonus, these selections also remain green throughout the winter. Many others turn bronze during this season.
- Location--Boxwoods won't grow in the Tropical South, so don't waste your time. In the Coastal South, Japanese boxwood (Buxus microphylla japonica) seems better adapted than other types.
- Nematodes--Common in moist, warm, sandy soils, nematodes are microscopic worms that feed on plant roots. They are a serious problem for boxwoods in Florida, causing large sections of foliage to yellow, wilt, and die. There is no easy cure. To put it simply, if your soil has nematodes, don't plant boxwoods.
So what should you do if your plant is ailing? Some can be saved, while others aren't worth the trouble. For a boxwood 3 feet tall or less, prune back the dead branches to live wood now. Also, open up the center of the plant. New growth will sprout this spring. At that time, sprinkle one or two cupfuls of a slow-release, natural fertilizer, such as cottonseed meal or Plant-Tone 5-3-3, around the shrub, and water it in. Eventually, the plant will fill out.
But if you have a huge boxwood with big dead spots and it's a slow grower such as English boxwood (B. sempervirens 'Suffruticosa'), it's time to face the music. By the time the plant grows back, you'll be pushing up daisies. Replace it with a new one.