The Homeowners Column

The Homeowners Column

Growing Lilacs

Photo of Sandra Mason

Sandra Mason
Extension Educator, Horticulture
slmason@illinois.edu

Mother's Day and lilacs, they just seem to go together. I guess when we were kids, it was either give mom a bouquet of lilacs or make her one more macaroni necklace.

The traditional lilac, Syringa vulgaris, is known for its wonderfully fragrant flowers. A lovely bouquet will easily fill a room with fragrance. Unfortunately that's their only real ornamental attribute. They tend to look gangly and unkempt most of the year. Throw in a little powdery mildew on the leaves and lilac shrubs leave much to be desired. It's probably best to tuck a few traditional lilacs into a shrub border or grouping in the landscape. They are definitely not good foundation plants.

The recent estimate is 2000 cultivars of common lilac. Most are in the pink, purple, blue or white range of flower colors with a few creamy yellows. There are a few listed as powdery mildew resistant such as 'Charles Joly' (magenta), 'Madame Lemoine' (pure white), 'President Lincoln' (true blue), 'Primrose' (creamy yellow) and 'Sensation' (purple and white bicolor).

Because lilacs tend to be long lived in the landscape, they may suffer from poor blooming eventually. The usual causes are:

  1. Too shady a site. All lilacs grow and flower best in full sun and well-drained soil.
  2. Pruning too late in the season and therefore removing the next year's flower buds. Common lilacs should be pruned immediately after flowering to keep them vigorous.
  3. Shrubs are in need of renewal pruning. Lilacs tend to bloom best on younger branches. Prune by removing about one third of the older branches down to the ground each year after flowering.
  4. Poor shrub vigor due to scale or borers. Usually removing the older stems will help to control these insects. Oystershell scale may require a spray of insecticidal soap or summer oil in late May. Be sure to read and follow all label directions.

Although the common or French hybrid lilacs are magnificently fragrant, there are superior lilac species for the landscape. In my opinion these landscape plants do not have quite the heady fragrance of common lilac, they are far better looking shrubs after they flower and tend to be free of powdery mildew. If you don't have much landscape space, these are better choices.

'Palibin' lilac is a neat, tidy shrub at five feet tall. The dark green leaves are smaller than common lilac. It may flower when quite young with pink lavender fragrant flowers. 'Miss Kim' lilac is a little larger at six feet. It makes a nice rounded shrub. It flowers a little later than common lilac with blue lavender flowers. The flowers are small but prolific. 'Miss Kim' usually develops a nice burgundy fall color, which is non-existent in common lilac.

Littleleaf lilac 'Superba' is also about six feet tall and like the other landscape lilacs forms a nice twiggy shrub. It has red buds that open to dark pink. 'Tinkerbelle' lilac might be worth growing just for the name. It has pink flowers on a five feet tall shrub. It has nice green heart shaped leaves.

If you want a lilac in tree form, then the Japanese tree lilac Syringa reticulata, is for you. It grows to twenty to thirty feet tall with a rounded habit. The bark is a lovely shiny red like that of cherry bark. It can be grown as a large shrub or small tree. It is resistant to powdery mildew and is highly resistant to the scale and borer insects. The white flowers are borne in dramatic panicles six to twelve inches long and six to ten inches wide. 'Ivory Silk' has particularly attractive bark and thick blue green leaves. 'Summer Snow' is listed as a particularly heavy bloomer.

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