When Do You Cut Back Boxwood for the Year?

When to Prune

• Boxwood shrubs are pruned in the spring. It is important to prune at a time when the shrub can produce new growth. Cutting back in the fall encourages new growth, which can succumb to winter damage. Three factors that act as exceptions to this rule: disease, damage and thinning cuts. Diseased portions of the boxwood are removed as soon as they appear, to keep the plant healthy and stop the disease spreading. Damaged boxwood is cut back when the damage occurs, to prevent harmful pathogens from entering wounds.

Diseases

• Boxwood is prone to fungal diseases caused by macrophoma and volutella fungus spores. Shrubs infected with macrophoma fungal diseases display symptoms such as leaf discoloration. Leaves from infected plants turn tan and are covered in black fungal spores. Volutella disease causes boxwood branches to turn from orange to tan. Generally, boxwood that is allowed to produce dense foliage is the most susceptible to these fungal diseases. Gardeners must cut back infected areas using pruning tools that have been sterilized, to prevent spreading.

Damage

• Damage can be caused by lawn mowers, wildlife, cars and harsh weather conditions. Often, damaged boxwood shrubs have torn branches and jagged leaves after experiencing damage. Torn branches create an entryway for diseases and insects to enter. To prevent further health problems, gardeners cut damaged areas back to healthy outward growing branches. Making 45 degree cuts to remove entire branches prevents water accumulation on stubs, which encourages fungal disease infection.

Thinning Cuts

• Thinning cuts differ from regular pruning cuts, because gardeners take less off the shrub. When gardeners thin out their boxwood, they remove 6- to 7-inch long branches that may be growing outside the planting area. Furthermore, gardeners thin or cut back branches growing inward or toward the ground. Annual pruning allows gardeners to remove as much as 50 percent without killing the boxwood. To prevent causing damage, gardeners must wait for the last frost for annual pruning.