Boxwood pruning is best accomplished by thinning the plant with hand pruners. Approximately 8 – 10% of the plant will be thinned out to allow for better light and air circulation, which will stimulate interior growth and allow for the further reduction of the plant at a later date if so required. This will also create an environment that is less likely to harbor pest and disease.
The best time to prune, especially with a reduction pruning, is during the dormant season after the coldest part of the winter has passed and before spring growth begins. If we have a mild winter, the pruning can be done in March. If we have an unseasonably cold winter, the pruning is best done at the beginning of April. Fertilizers can be coupled after pruning for optimal results.
Shearing is an improper pruning practice of boxwoods, as it stimulates outer canopy growth and creates a dense layer of leaves. This shades the interior of the plant causing it to shed its leaves which will further impede reduction work in the future.
Cleaning and removing the leaf litter (dead leaves that have accumulated over time under the boxwoods) out from the base of the plant. The leaf litter holds moisture in and around the trunk and branch tissue which can damage it. This also provides the perfect environment to harbor pathogens and insect populations.
A one to two-inch layer of mulch should be installed under the plants to retain soil moisture and regulate the ground temperature.
Multiple pests can affect boxwoods. The most common are psyllids, mites and leaf miners. Leaf miners can do the most harm and defoliate a plant within 2 to 3 years. If you notice a problem, have your local arborist stop out for a look and recommend a treatment.