Lilacs

Common Lilac
(Syringa vulgaris)
May 11, 2006

Lilacs especially the deep pinky, purplish ones are one of my favourite flowering bushes. As a child I used to climb one of our lilac trees and sit in a cradle formed through pruning. Hidden from view and cooled by the dark leaves I spent many a summer afternoon reading. With the exception of our first house there has been at least one lilac bush in every house we've owned. We have a small thicket of common lilac here.

The common lilac (Syringa vulgaris) and the smaller hybrid Persian lilac (Syringa x persica) are large deciduous shrubs that range in size from 2 to 10 m. Originated in Europe and Asia, they became popular in New England botanical gardens in the 1750's. A lilac bush can live for hundreds of years! Lilacs bloom in the spring filling the air with their heavenly, sweet scent. Lilacs are relatively maintenance free and very easy to care for. Many believe that lilacs should be pruned however, blooms form on old wood so the bush will produce more flowers if left unpruned. A pruned bush will produce few flowers but fast growing stem growth and may not bloom well for as many as five years after pruning. An unpruned lilac bush will flower profusely every alternate year. Blooming can be encouraged by deadheading after the colour fades but before seeds are formed. Blooms range in colour from white to a pale, bluish purple to a deeper pinky purple as shown in the photo. One lilac cultivar (Aurea) has yellowish flowers. Some cultivars have double flowers rather than the single flowers in the photo.

Lilacs produce secondary suckers from the base and roots of the shrub. If left these will produce a thicket that if not disturbed will remain long after buildings on the property are removed. This tendency makes lilacs the perfect choice for camouflaging unsightly fences or forming a living privacy screen. If you don't want a thicket forming, simply remove the secondary suckers as they appear.

Lilacs are subject to the powdery mildew Erysiphe syringae in late summer although some cultivars are more resistant than others. Humid air, over fertilizing, overcast days and irrigation are conditions that favour powdery mildew. This disease will be more severe in dense plantings and for lilacs planted in damp, shaded areas. Once infected the leaves may drop prematurely but aside of aesthetics this does not harm the bush. A variety of fungicides are available in some areas to control this powdery mildew but should only be used if the disease occurs in the spring or early summer. If powdery mildew occurs late summer there is no need to treat. Some biological control can through a variety of insects and snails that feed on the spores. The best way to prevent powdery mildew on lilacs is to plant where the bush will get good air circulation.

Happy Gardening!

Garden Gnome
©2007