When to Prune Holly Bushes
Prune holly in late winter while it is dormant, before spring growth begins. This shapes the plant without sacrificing berries, since holly flowers — and later fruits — on the previous season's wood. Light shaping is also fine in early summer after new growth hardens.
The best time to prune holly is late winter, during dormancy and just before the plant pushes new growth. Pruning then lets you shape the shrub and remove dead or crossing wood while the structure is easy to see, and it does the least harm to the coming season's flowers and berries.
Timing matters most on female hollies grown for fruit. Holly blooms in spring on wood formed the previous year, and those flowers become the winter berries. Prune too heavily in late spring and you remove the developing fruit. If you want cut greenery, the neatest solution is to harvest berried branches in December — that is simply winter pruning with a holiday bonus.
Light trimming to shape a hedge can also be done in early to midsummer, once the spring flush has firmed up. Avoid pruning in late summer or fall, which can force soft growth that winter cold will damage.