Tips for Pruning Spring Blooming Shrubs

Like many spring-blooming shrubs, lilacs bloom on old wood, which means they set next year's flower buds shortly after they finish blooming this year. If you wait too long to prune them, you will remove many of next year's blooms. As a rule, plan to prune within two weeks after the shrub stops blooming. Other shrubs that fall into this category include forsythia, ninebark, spring-blooming spirea, and viburnums. Proper care for these spring flowering shrubs includes deadheading, pruning out old, diseased wood and in some severe cases, rejuvenation pruning.  

Deadheading involves removing the spent blossoms from this year's bloom. 

In the case of lilacs, the old flower cluster should be cut off at its base, just above the two fresh shoots that emerge from the same branch as the faded flowers. While you’re at it, remove any old seed pods. New shoots will grow over the summer, set flower buds and be topped off with a flower cluster the following spring.

Prune forsythia back to a healthy pair of outward facing leaf buds. Prune ninebark about one-quarter inch below the spent bloom. Prune spirea back to just above the topmost leaf.  

 

 

This is also the time to get rid of dead, damaged or diseased canes, as well as any branches that cross one another.  

If indeed, your lilac has seen better days, rejuvenation pruning may be in order. One way to renew a large, overgrown shrub is to remove one third of the canes every year over a three-year period.  A more drastic approach involves cutting every cane back to 4”- 6” above the ground. This will result in many vigorous canes the following season, but it may only produce leaves the first two years.  If your lilac bush is of the grafted variety, be sure and cut above the graft. These care instructions are for common lilacs (Syringa vulgaris). Dwarf lilacs such as ‘Miss Kim’ seldom need pruning, other than deadheading as the blooms fade. 

Finally, work in 2” of Earth Essentials sheep, peat and compost; add a balanced fertilizer, such as 11-15-11 and mulch to about 3”. Your lilac and other early flowering shrubs will be prepared for the rest of the summer and ready to bloom next spring.