When can I prune boxwoods?
The Gardener’s Answer
Boxwoods (Buxus) are versatile and can be used in formal or informal gardens. These evergreens do not require annual pruning, but dead or diseased branches should be pruned out regardless of the time of year. Older plants with dead lower branches will benefit from being thinned. This will allow more light and air to move through the plant.
If you are creating a topiary or pruning to thin, shape, or rejuvenate, the best time to do this is late spring/early summer after they have finished putting on new growth for the season. Pruning too early in the spring while they are putting on new growth is fine, but it will only encourage more growth. So, if you do prune too early you may have to get your tools back out later in the season.
The only time you want to avoid pruning these evergreens is during the late summer/fall. Prompting new growth at this time of the year will make the plant more susceptible to winter damage, since the tender growth may not have time to harden off before the cold temperatures arrive. As with any pruning job, make sure that your tools are clean and sharp. Sit tight for now and put this on your to-do list for next summer.