Boxwoods are slow-growing evergreen shrubs that are grown for ornamental purposes. While boxwood grows slowly, it does need to be shaped at least yearly. Shaping your boxwood allows you to grow a healthier plant with dense, bushy leaves.
Prune only when temperatures are above freezing. Boxwoods are not cold resistant and the stress of pruning and cold temperatures can kill the plant.
Thin the outer branches to allow light to penetrate through to the interior of the bush. Do this whenever you see a dense outer shell of foliage has formed, blocking the light to the interior of the bush. Thin the tops and the sides of the boxwood to allow leaves all the way through the interior to get light.
Trim back the longest shoots and branches that break away from the main foliage. This helps the boxwood maintain its form. Trim only one side of the plant if the boxwood needs heavy pruning. If necessary, wait a full year until you trim down the second side. This allows the plant to recover.