You should actually prune your spirea more than once a year, at least twice. Give it a good trim after it flowers in the spring by cutting back the tips of the stems to the top leaf bud. This removes the dead blossoms and also may trigger a second blooming and new leaf growth.

Can I cut my spirea to the ground?

The spirea species (Spiraea spp.) ... To control the spirea's size and keep it blooming year after year, you should prune it back after blooming or when it's dormant in winter. If it's severely overgrown, cut it to the ground to rejuvenate the shrub.

How far down can you trim a spirea bush?

3. Prune spirea to get big flower clusters. Spirea that's not pruned or pruned to the ground each spring has a casual, loose habit. In early spring, before the leaf buds start to swell, cut all of the stems down so they're 4 to 6 in.