How to prune clethra alnifolia

Late winter to early spring before new growth emerges. Cut dead and crossing stems back to the base. On established, congested clumps, remove up to one-third of the oldest canes at ground level each year over three years, or cut the whole plant hard down for full rejuvenation.

Annually for light tidying; hard rejuvenation every 5–7 years. Clethra alnifolia (summersweet) responds well to annual light pruning. Remove dead stems and the oldest, woodiest canes at ground level in late winter to encourage vigorous new shoots and strong summer blooms. Plants that have become congested can be rejuvenated by cutting all stems to 6–12 inches in early spring.

Cut dead and crossing stems back to the base. On established, congested clumps, remove up to one-third of the oldest canes at ground level each year over three years, or cut the whole plant hard down for full rejuvenation.