How to prune spiraea nipponica 'snowmound'

Immediately after flowering, early to mid-summer. Shorten flowered shoots back to a healthy lateral bud or branch. Remove the oldest, most congested stems at ground level to open the centre and encourage fresh growth.

Annually after flowering; renewal thinning every 3 years. Snowmound spiraea blooms on old wood in late spring, so timing matters. Prune immediately after flowering finishes — usually early summer — cutting back flowered shoots to strong side buds. Avoid autumn or winter pruning, which removes next season's buds. Every few years, remove one-third of the oldest stems at the base to renew the shrub.

Shorten flowered shoots back to a healthy lateral bud or branch. Remove the oldest, most congested stems at ground level to open the centre and encourage fresh growth.