Perhaps the best known lilac species is common lilac (Syringa vulgaris), represented by the hundreds of cultivars within this species. Common lilacs bear large, fragrant flower panicles composed of many small individual florets that have either a single or double form. Cultivars are classified by flower color.

In the late 1800s the Lemoine nursery in France introduced many new cultivars to the world—the term “French Hybrids” is often still used in nurseries in reference to all common lilac cultivars.

The lilac species Syringa oblata subsp. dilatata is notable in two seasons. It is one of the earliest blooming lilacs in the spring (before common lilacs), bearing large clusters of pretty pale pinkish lavender florets. It shines again in autumn when its foliage develops bronze to purplish tints—one of few lilacs that show fall color. The cultivar ‘Cheyenne’ has especially nice fall foliage.

Most lilacs have simple, unlobed leaves with a rounded, oval, or obovate shape, but within the lilac collection you may notice a couple of exceptions. Afghan lilac (Syringa protolaciniata) and its cultivar ‘Kabul’ have simple leaves that are laciniate (deeply lobed), though the degree of laciniation can vary from leaf to leaf. Even more unique is Syringa pinnatifolia, the only lilac species with compound leaves.

Dwarf Korean lilac (Syringa meyeri ‘Palibin’) is one of the smallest lilacs in the collection, growing only about 3 to 4 feet tall and wide. It is densely twiggy, fine textured, and has a neatly rounded habit. In mid to late spring dwarf Korean lilac is covered with a profusion of short flower panicles; the small florets are light lavender pink.

Most lilacs grow as multi-stemmed shrubs, but several species grow as small trees with one or a few main trunks. Japanese tree lilac (Syringa reticulata) is a popular tree-form lilac, and a venerable 1876 specimen (accession 1111*A) of this species is the oldest lilac at the Arboretum. Japanese tree lilac blooms several weeks later than common lilacs and bears large terminal panicles of very small, creamy white flowers.