Lilacs: Versatile and Attractive Flowering Shrubs

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Lilacs are versatile and attractive flowering shrubs with a wide range of uses. They make attractive border plantings, accent plants, windscreens or flowering hedges since both the plants and flowers are attractive.

Although lilacs have delicate blossoms, the plants are among the hardiest ornamentals. Some varieties survive winter temperatures down to minus 60 degrees Fahrenheit and are perfectly hardy in Utah.

Lilacs prefer alkaline soils, which we have in rich abundance. They tolerate extreme neglect and continue to flower for many years with almost no care. Typically the only thing they need is an occasional pruning to keep them within bounds.

As the name implies, most lilac flowers are lavender, but the flowers range from magenta to pink to true lilac, blue, violet and even white. Their different bloom seasons provide blossoms and fragrance from April through June. Plant heights range from 3 to 30 feet, although most varieties have a maximum height of approximately 10 feet.

Because of the many species and the kinds of lilacs, it is often difficult to categorize them accurately. Extensive cross breeding had blurred the lines between the species and they are sometimes difficult to identify. They all belong to the genus Syringa and most lilacs have unlobed leaves and flowers that grow in clusters.

Lilacs grow best in full sun and well-drained soil. Since they are large plants, they need plenty of room. They thrive in open, exposed areas and tolerate wind. They grow well in most garden soils, but do not like soils that are too rich, so avoid over-fertilization, as it produces lots of foliage and very few flowers.

Plants require minimal irrigation and are actually quite drought tolerant, although adequate water increases both the quantity and quality of blooms and makes the plants much more attractive.

Lilacs should not be over-pruned or sheared on top. Pruning is generally unnecessary for the first three or four years. Let the plants develop several branches at the base and then remove the older branches by renewal pruning when they have grown too tall.

Remove the weaker wood from the center of the bush and if the plants get too old and overgrown, remove one-third of the oldest wood each year for three years to renew the shrub. Lilacs should be pruned after they finish flowering, as spring pruning does nothing but remove the potential blossoms.

The practice of removing dead flowers soon after they wither to help prevent the seed pods is often recommended but less practiced because of the work involved.

Lilacs are reasonably pest-free and require only minimal attention to pest control. The most serious pest is the lilac borer. It is the larvae of a clear winged moth that attacks the old branches. The borers become active during the first part of May and can be prevented by spraying the trunks with an approved insecticide.

They can also be controlled organically by pruning out wood that is over three years old. This keeps the wood vigorous and upright and keeps it producing abundant blossoms. The borers only attack the older wood, so pruning prevents serious infestations.

Scale also attacks lilacs. The pests pierce the bark, suck the sap and reduce the plant vigor. Scale insects are best controlled using a dormant oil or by carefully monitoring the pests and treating when the scale is in the crawler stage.

Strawberry root weevil also attacks lilacs and makes notched edges on the leaves. Apply an insecticide at the base of the plant as the pests become active in early summer.

Powdery mildew is one of few serious diseases that we see on lilacs in our area. Because it generally appears in the late summer, we usually do not control it. If it appears earlier in the season, it can be controlled with an approved fungicide.

Use lilacs as tough yet attractive plants that tolerate our alkaline soils and harsh temperatures. Choose from some of the many different kinds available to solve problems and create beauty in your yard.