Problems With Buxus Sempervirens

Buxus sempervirens, commonly called American boxwood, common boxwood or common box, makes its way into landscapes across the country due to its hardiness, shade tolerance and ability to handle even severe shearing. This species grows in U.S. Department of Agriculture plant hardiness zones 6 through 8; some gardeners in USDA zone 5 may have luck with this specimen plant, as well. Despite its functionality, common boxwood is prone to a handful of problems.

Common boxwood is a slow-growing shrub that typically reaches between 6 and 8 feet tall; very old specimens that are well cared for may grow to 20 feet. This evergreen shrub's foliage consists of small, ovate leaves that give the shrub its characteristic soft appearance. Gardeners commonly use this species and its many cultivars as formal hedges, foundation plantings or bed borders.

A handful of pests and diseases affect boxwood, although this species is tolerant of most. Problems rarely -- if ever -- need reconciling, with the occasional exception of leafminers and winter burn.

Boxwood leafminers are common pests of this plant. These tiny insects -- actually maggots of a small, orange, mosquito-like fly -- mine the leaves, leaving discolored swirls and trails along leaf surfaces, along with blisters on the undersides of leaves. Other signs of leafminer activity are the orange adults buzzing around boxwoods in mid-spring, as the temperatures begin staying warm during the day and early summer-blooming perennials start flowering.

Leafminers overwinter on the leaves and emerge as adults in spring as the boxwood's new growth starts to appear. Adults mate and females then deposit eggs on the undersides of leaves.

To reduce the number of these pests, prune foliage in late winter before the adult flies emerge in early spring, or just after the eggs are laid in mid- to late-spring. Unfortunately these eggs are very small and are inserted into the undersides of leaves; however, once you notice adult activity, eggs are likely being laid. Inspect leaves carefully for signs of the tiny eggs or larvae; if you notice any, pinch the leaves together to crush the larvae inside.

Several [cultivars](http://www.hort.uconn.edu/plants/detail.php?pid=75) of this species are more resistant to these leaf miners, particularly '[Suffrutiosa](https://plants.ces.ncsu.edu/plants/all/buxus-sempervirens-suffruticosa/)' (_Buxus sempervirens_ 'Suffrutiosa'), which grows in USDA zones 5 through 8.

Other pests include boxwood psyllids. These insects are very small. When the nymphs feed, boxwood leaves curl into a distinctive shape. The damage is primarily aesthetic and does not require treatment.

In sandy soils in hot climates, such as those in the South, root nematodes may cause some concern. Leaves start to bronze and the entire plant will begin to decline. You cannot completely get rid of nematodes. Grow grasses and annual marigolds (Tagetes spp.), both of which are resistant to nematodes, to help reduce nematode populations.

Among the most common problems with boxwood is winter damage; the leaves bronze in cold, harsh winters in the northern parts of its range. For this reason, plants in USDA zones 5 and 6, sometimes 7, should be in an area protected from strong winter winds. Water your boxwood at least 1 inch per week into early winter until the ground freezes to help prevent winter dessication. Recovery can take several years. Sectional burn on a boxwood requires pruning affected branches back to where the bark stops splitting in late winter or early spring, when temperatures begin warming up but before new growth appears.

Another issue is root rot. This problem occurs when the soil remains too wet; boxwoods need a site with well-drained soil. Over-watering is a major cause of this disease, as is waterlogged soil. The roots will begin to rot and become dark. Above the soil surface, your boxwood's bark will start rotting and peeling away. Once above-ground symptoms have appeared, it is hard -- sometimes impossible -- to control. The whole plant often dies.

If you have experienced root rot with boxwoods in a particular location, do not plant the same variety in that location.