In Toronto and area Spirea shrubs (Spirea spp.) are used in a lot of gardens because of attractive foliage and multiple clusters of small, colorful flowers. Spireas produce flowers on new wood and many varieties may bloom a second time after a light pruning, while others, like Japanese spirea (S. japonica), respond better to a late-winter trim. Pruning can also maintain the shrub’s size and rejuvenate overgrown plants.
1. Cut back the tips of most spirea varieties immediately following the first flush of spring flowers (mid to late April). Trim the stem tips back to the topmost leaf bud on each stem, using clean shears. Maintain the shape of the shrub as you prune. Tip pruning removes the dead blossoms and may encourage new flower bud formation.

2. Prune overgrown shoots and stems at any time during the summer growing season to maintain the shrub’s shape. Make the cuts within 1/4 inch of a leaf or bud when possible. Cutting an overgrown stem slightly shorter than the surrounding stems helps camouflage the cut edge.

3. Trim back overgrown spireas or those that produced sparse foliage on the lower stems severely in fall after the foliage begins to fall off, to keep the shrubs small and compact. Cut back each stem to within 8 to 12 inches of the ground. In spring, a severely pruned spirea grows new stems that are all capable of flowering.

4. Examine the spirea shrub in late winter after the buds begin swelling but before they leaf out, for dead or damaged branches. Remove all dead and damaged wood, along with any branches that cross or rub together. Japanese spirea varieties require tip pruning at this time.