Prune lilacs next spring, not now

Q. Can I prune my lilacs down for height this time of year?

Thelma from Canfield

A. Yes, you can, but if you want all of your flowers next year, the answer changes to a loud NO!

The common lilac, Syringa vulgaris, is a spring-blooming shrub. Most spring-blooming shrubs form their flower buds from August to October. So whatever you prune now will include those flower buds for spring 2015. Your best bet is to wait until after the lilac blooms next spring, then selectively prune the shrub back to the height you want. In general, you prune plants just after they bloom (but there are exceptions).

Lilacs are often left to bloom for years without pruning. The result is large lilac shrubs with few blooms. The blooms that do emerge in spring are too high to reach when trying to cut the flowers to bring into the home.

Many older homes and older landscapes have very large lilacs (over 8 feet tall). These are often crowded with lots of stems coming from the ground and lots of foliage, with most of the bottom leaves covered with powdery mildew this time of year. If this describes your lilacs, they need a good pruning. But they do not need a complete renovation, which would be a severe cutting and removal of many stems. This will result in the elimination of blooms, and while it may renovate the shrub, you’ll have an ugly plant for a few years.

The best option for large lilacs is pruning a little here and there each year. Simply cut out 3-5 of the largest stems (usually in the center of the shrub). Go by the general rule of cutting one-third of the largest stems. These should be cut down to the ground. If you do this each year, you’ll be rejuvenating it but will continue to enjoy flowers each year.

If you have a smaller lilac, it is most likely a “Miss Kim” (Syringa patula “Miss Kim”). This compact shrub is pruned differently. Simply reach into the center and thin it by removing a few stems to allow for more air movement throughout the plant canopy. To learn more about when to prune specific plants, go to: http://go.osu.edu/pruneshrubs.

Eric Barrett is OSU Extension educator for agriculture and natural resources in Mahoning County. Call the office hot line at 330-533-5538 from 9 a.m. to noon Mondays and Thursdays to submit your questions.