Syringa vulgaris

Common lilac is a spring-flowering, perennial shrub or small tree in the olive family (Oleaceae). There are hundreds of cultivars available including single and double flowers of various colors including white, cream, rose, magenta, pinkish-purple, lavender, and purple. The specific epithet is Latin for “common.”

Lilac does best in cold winter climates, as they require a long period of winter chill for the buds to mature. Some “low chill” cultivars have been developed, but even these perform best when they get an extended, cold winter rest. Late frost will sometimes kill the buds, so it is best sited in a protected location. It is tolerant of different soil types but does not do well in soil that is highly acidic or poorly drained. Most plants are grafted, so suckers should be removed from the rootstock to maintain the appearance and prevent unwanted spread. 

This plant grows rapidly to fill its space. It makes excellent cut flowers, but after its spectacular mid- to late-spring bloom, the shrub is of little interest in the landscape. Its branches are leggy, and its foliage is susceptible to powdery mildew. Common lilac has value to wildlife as the caterpillars of several moths feed on the foliage, including the Promethea silkmoth (Callosamia promethea), Royal Walnut Moth (Citheronia regalis), and Laurel sphinx (Sphinx kalmiae).

Common lilac can be used in a variety of landscapes where its spring flowers can be admired but its summer foliage can blend in with surrounding shrubbery. It is appropriate for cottage gardens, children’s gardens, or butterfly, edible, or cutting gardens. The pungently sweet fragrance is delightful but can be overpowering to some individuals. 

Interestingly, President Thomas Jefferson wrote about his love of lilacs in his gardening book. They are also the state flower of New Hampshire. 

Insects, Diseases, and Other Plant Problems:  Insect pests include scales, borers, leaf miners, thrips, and caterpillars. Powdery mildew can seriously affect the appearance of the foliage in the summer but does little permanent damage to the shrub. Prune the center of the plant to help with the airflow. Additional disease problems include blights, leaf spots, wilts, ringspot virus, and honey fungus.