Then the following year do that again and then the third year.
Jan 25, Boxwoods can be pruned any time but late summer and early fall.

This is because pruning then will spur new growth that won't harden off in time for winter and be killed by the cold. Severe late summer pruning followed by a cold winter could even kill the entire stumpdelimbing.club: Steve Bender.
Dec 28, While dead, diseased or broken boxwood branches can be removed any time you notice them, begin renewal pruning in late winter to early spring, Missing: Keller TX.