Care of Boxwood Plants

Boxwood plants (Buxus spp.) have been prized for centuries as hedges, shrubs and ornamental statement pieces. Their compact, dense growth and dark green, glossy foliage was traditionally used in formal gardens on historic Southern estates. Today, boxwoods can add a hint of vintage flair to any landscape.

Almost 100 kinds of boxwood exist around the world, but only three main varieties and their associated hybrids are typically used in landscapes and gardens today:

Littleleaf boxwood (Buxus microphylla), which grows in U.S. Department of Agriculture plant hardiness zones 6 through 9. This boxwood grows 3 to 4 feet tall with round, leathery leaves and hard-to-find, yet fragrant, petalless blossoms.

Common or American boxwood (Buxus sempervirens), that -- true to its name -- is the most common kind of boxwood with more than 400 cultivars. Examples include 'Green Gem' in USDA plant zones 4 through 9 -- it grows up to 2 feet tall, making it ideal for small yards -- and the 'Edgar Anderson' variety in USDA plant zones 6 through 8. The latter cultivar grows up to 6 feet tall, making it better for large landscapes.

Korean boxwood (Buxus sinica var. insularism), which grows in USDA plant hardiness zones 4 through 9. Korean boxwood grows up to 2 1/2 feet tall but at an exceptionally slow rate of less than 2 inches per year. This type of boxwood is one of the hardiest versions available and produces yellow-green to dark green foliage with yellow, aromatic flowers. 

Boxwood shrubs can survive in full sun but do best in partial shade. When it comes to sunlight assessment terminology, keep in mind the following definitions:

Full sun: Six or more hours of sunlight daily.

Partial sun: Four to six hours of sun.

Partial shade: Two to four hours of sun.

All boxwood shrubs thrive in well-drained soil. Chronically wet, waterlogged soil will kill these otherwise hardy plants.

Before planting a boxwood, mix 3 to 4 inches of compost into the top 12 inches of soil at the planting site. As a soil amendment, boxwood-friendly compost benefits include:

Improving how quickly the soil drains.

Enhancing soil aeration.

Increasing soil nutrient levels.

During their first year after being planted, boxwoods need consistently moist, but not soaking wet, soil. Water the plants whenever the top couple of inches of soil have dried out. Moisten the soil to a depth of 6 to 8 inches. Compared to many other shrubs, boxwood shrubs have unusually shallow root zones.

Once established, a boxwood doesn't need frequent watering. Water the shrubs whenever it has rained less than an inch in a week.

Conserve water by using mulch, such as shredded leaves or wood chips. Spread 2 to 3 inches of mulch around the boxwood shrub, extending from the base of the plant to the foliage canopy -- the soil that's just below the farthest tips of the boxwood's branches. Mulch keeps the shrub's roots cool, conserves soil moisture and minimizes weed invasions.

Annual fertilization increases boxwood growth and vigor, resulting in a healthier, denser shrub and more vibrant foliage and flowers. Fertilize in the early spring before the plant begins to produce new growth. Use a 10-10-10 or similarly balanced all-purpose fertilizer at a rate of 1/2 lb. for every 50 square feet. Sprinkle the fertilizer evenly over the planting site, but keep the fertilizer at least 6 inches away from the base of each plant to avoid fertilizer burn.

Just one fertilizer application per year is typically enough unless you have sandy soil. If that's the case, fertilize once more in the late spring.

Boxwood do not require pruning. Occasional thinning every two years, however, can help open up the shrub's dense growth to let in light and improve air circulation, which in turn reduces the risks of plant diseases.

Avoid trimming boxwood in the late summer or early fall; any other time of the year is fair game. Simply cut 3 to 6 inches off of the growing tips of every other branch throughout the outer edges of the shrub.

Don't forget to sterilize pruning shears before trimming the boxwood to prevent the spread of disease. Combine equal parts rubbing alcohol and water in a bucket and soak the pruning shears for five minutes. Rinse the shears under fresh water and allow them to air dry.

Boxwood plants occasionally suffer from a variety of diseases and pests. Examples include blight, boxwood decline -- a not-very-well-understood disease thought to be caused by various fungi -- and root rot. Prevention and treatment techniques that help with most boxwood diseases include:

Avoiding overwatering and underwatering. The former encourages boxwood decline, rotting and blight, while the latter increases plant stress and makes the plant more susceptible to all diseases and pests.

Pruning the plants every couple of years. This increases air circulation and sunlight penetration, helping to prevent boxwood decline and other diseases.

Trimming off dead or injured plant stems and branches. This prevents boxwood decline, blights and more.

Avoiding overfertilization, which increases the risk of boxwood decline.

When it comes to boxwood pests, common insects include psyllids, mites and other soft-bodied pests. Insecticidal soap, available garden stores and nurseries, controls this problem. Instead of buying a commercially prepared product, mix your own homemade insecticide.

Clean spray bottle

Measuring spoon

Liquid dish soap

Pour 2 teaspoons of liquid dish soap into a clean spray bottle and add 1 pint of water.

Spray the soapy solution onto the boxwood plant, focusing on all exposed areas suffering from pests. The soap must come in direct contact with the insects to kill them.

Rinse the boxwood plant with fresh water a couple of hours after treatment. This reduces the risks of the soap causing lasting plant injury.

Repeat the soapy spray application four to seven days later if insect activity resumes.

Check the undersides of leaves for pests. This is a common area where insects tend to congregate.