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Tuesday - February 19, 2008

From: Elm Grove, WI
Region: Midwest
Topic: Non-Natives
Title: Care for a non-native Syringa vulgaris (lilac)
Answered by: Barbara Medford

QUESTION:

I inherited a lilac bush when I bought my house. It grows in a bed right in front of the house but grows away from the house, not in a straight up and down manner. This winter we had a 12" snow fall and it bent the limbs way over and makes it looks terrible. The previous spring I had pruned the bush in hopes that it would get bushy but it did not. I imagine it is a pretty old bush. I am wondering if and how I can prune it to make it more bushy and vertical.

ANSWER:

The common lilac, Syringa vulgaris, was brought to the United States from Europe in the 1700's; it originated in Asia. At the Lady Bird Johnson Wildflower Center, our focus is on plants native to North America; however, we always try to help when an existing plant is having problems. The lilac is grown for the fragrance and beauty of the flowers, which only last about 2 weeks in the Spring, and not the foliage.

First, let's check the existing conditions. The lilac is considered hardy in USDA Hardiness Zones 3-7. Since your area in Wisconsin appears to be in Zones 4a to 4b, you're safe there. Next, the lilac requires full sun. If it is next to your house, and trying to grow away from it, it could be shaded by the house, and be reaching for more sunlight. Possibly large trees are shading it, and limbing up those branches keeping the sun off your bush could help; but that's pretty extreme, especially if they are very large trees. The lilac is prone to powdery mildew disease. To help prevent this, provide good circulation by keeping branches pruned. Also, cut off dead flowers as soon as they finish blooming; this will prevent seed from forming and promote more profuse flowering for next Spring. For more detailed care of your plant, go to this Gardener's Network website How to Grow Lilacs-Care and Feeding.

If you decide that your lilac is simply too close to the house, or too shaded, and want to replace it, might we suggest some North American natives that are found in Wisconsin, and able to get through the winters. The advantage of native plants is that they are already adapted to the conditions, and will need less fertilizer, water and pesticides, all of which can result in unnecessary runoff and end up in your drinking water.

Desmanthus illinoensis (Illinois bundleflower) - blooms May to September

Physocarpus opulifolius (common ninebark) - blooms May and June

Rhus copallinum (winged sumac) - blooms July and August

Viburnum acerifolium (mapleleaf viburnum) - Blooms April to August

Desmanthus illinoensis

Physocarpus opulifolius

Rhus copallinum