Expert: C.L. Fornari - 10/15/2006

Question
I live in NJ and have lilacs planted in the ground.  Can you recommend the proper way to maintain these bushes?

Answer
Sergio,
Liliacs are one of the easiest shrubs to grow - as long as they are in full sun, and are planted in a place where they can grow to their full height and width, they are very reliable and low-maintenance plants.  Lilacs need to be growing in a neutral pH soil in order to bloom, so most gardeners in the Northeast (where we have acid rain) put a cup of lime or four to five cups of wood ashes, around the plant every year to maintain the proper pH.  If you have good soil (not pure sand) there in NJ you shouldn't have to fertilize, but if you have sandy soils you can also provide an annual application of an organic fertilizer.  All plants appreciate a top dressing (an inch put on the surface of the soil) of compost or composted manure every year.

Lilacs are prone to powdery mildew, a greyish coating on the leaves that appears in mid to late summer.  On lilacs this is a cosmetic problem only...it doesn't hurt the health of the plant.  But if you don't like how it looks, spray the plant with a product called GreenCure starting at the end of June and repeating every ten days to two weeks.  GreenCure is a very least-toxic treatment and it is available through garden centers or on-line stores.

If you need to prune lilacs, do so right after they bloom, but the ideal with this plant is to do no pruning except cutting out dead wood, odd or funky looking twigs or branches, and excess straight shoots that appear around the main stems although this is optional - these so called "suckers" do not hurt the plant and in fact make the clump larger...they can be left in place if there is room for the plant to expand.

I hope this helps!
C.L.