We love our lilac shrubs with their exemplary fragrance in May. But almost any lilac that has not been pruned for two years or more is likely to have several trunks, some older than others, and a brood of basal shoots (“suckers”) around its base. And as it blooms on branch tips, we might find most flowers up high, out of optimal sniffing range. Pruning to meet these challenges can be a different approach than with many other flowering shrubs.
Common lilac (Syringa vulgaris) can grow anywhere between 8 and 20 feet tall and wide, depending on its cultivar. If it is given plenty of space, pruning may not be necessary outside of occasional deadheading and thinning. But if your lilac is planted in close quarters (now, who might have done that?) or if you otherwise wish to restrict its size, here are some methods to try.
Goals of Pruning Lilacs
Typically, lilac pruning aims to meet any combination of the five following goals:
Deadheading – removing spent blossoms and seedheads to visually clean it up and increase blooming potential for next year.
Removing or minimizing basal shoots (suckers).
Reducing the shrub’s size to encourage lower blooms where we can more easily enjoy them.
Thinning the shrub to preserve its tree-like character.
Starting over – renovating it from the ground up.
Note that some dwarf and specialty lilacs do not exhibit the same size issues or suckering, but many of these same pruning principles apply. They also work on a host of other multi-trunk shrubs. For an overview of basic pruning principles, check out our earlier post, Pruning 101.
Here’s an image of a moderately mature common lilac that can use a little maintenance. It has older trunks (showing the more mottled, gray bark), younger trunks (smoother, tan bark), spent blooms with seedheads, and a healthy crop of basal shoots.