When to Prune
Because the Winter Gem boxwood shrubs are evergreen and hardy to around 20 degrees below zero Fahrenheit, you can prune them at nearly any time of year and they will still recover heartily. In general, most pruning is done in late winter or early spring, while growth is slow due to the cold weather. This way, once the weather begins to warm in later spring, healthy new growth will sprout from the pruned areas. However, if you run into areas growing out of control, or branches that become damaged or infested with mold or insects throughout the growing season, you can also prune then.
When you prune, start with removing any dead, damaged or diseased branches from the shrub. These branches may undergo damage from high winds or intense freezes and thaws throughout the winter, and damaged or dead plant material will attract mold and insects as the spring sets in. From there, you need only to prune to control size and shape. For example, you can remove branches that are crowding other plants or coming too close to a house or fixture. You can also simply trim back these branches to fit the desired look of your boxwood. When left to grow on their own, Winter Gems take on a generally pyramidlike shape.
Because they can withstand heavy pruning nearly any time of year, Winter Gem boxwoods respond well to shearing. Shearing is the process of removing all growth that grows out beyond a certain size or shape. Because this often involves removal of a lot of plant material, it can be done with electric shearers, or with hand pruners, though that will take longer. Many landscapers shear these shrubs to take on a circular or boxy shape to serve as landscape markers or decorative fixtures in the garden. As long as you don't remove more than half of the plant's total material in a single season, the Winter Gem will recover.
Winter Gem boxwood can recover from pruning nearly any time of year, but damage is reduced when you avoid pruning when new growth is rapidly exposed to winter weather. If at all possible, try not to prune after mid-summer, as there is a greater risk of the young new growth being damaged in the upcoming cold of winter. If you have to remove branches or stems infested with mold, disease or insects, clean your pruning shears between every single cut with rubbing alcohol to avoid spreading the damage from plant to plant, or from branch to branch in the same plant.