They are small trees, ranging in size from 2 to 10 metres (6 ft 7 in to 32 ft 10 in) tall, with stems up to 20 to 30 centimetres (7.9 to 11.8 in) diameter. The leaves are opposite (occasionally in whorls of three) in arrangement, and their shape is simple and heart-shaped to broad lanceolate in most species, but pinnate in a few species (e.g. S. protolaciniata, S. pinnatifolia). The flowers are produced in spring, each flower being 5 to 10 millimetres (0.20 to 0.39 in) in diameter with a four-lobed corolla, the corolla tube narrow, 5 to 20 millimetres (0.20 to 0.79 in) long; they are monoecious, with fertile stamens and stigma in each flower. The usual flower colour is a shade of purple (often a light purple or lilac), but white, pale yellow and pink, and even a dark burgundy color are also found. The flowers grow in large panicles, and in several species have a strong fragrance. Flowering varies between mid spring to early summer, depending on the species. The fruit is a dry, brown capsule, splitting in two at maturity to release the two winged seeds.
The English common name "lilac" is from the French lilac via the Arabic ? ("lilak") from Persian ? ("nilak") meaning "bluish".
Cultivation and uses
A white, double-flowered cultivar
Dormant lilac buds
Lilacs are popular shrubs in parks and gardens throughout the temperate zone, and several hybrids and numerous cultivars have been developed. The term French lilac is often used to refer to modern double-flowered cultivars, thanks to the work of prolific breeder Victor Lemoine. Lilacs grow most successfully in well-drained soils, particularly those based on chalk. They flower on old wood, and produce more flowers if unpruned. If pruned, the plant responds by producing fast-growing young vegetative growth with no flowers, in an attempt to restore the removed branches. Lilac bushes can be prone to powdery mildew disease.
The wood of lilac is close-grained, diffuse-porous, extremely hard and one of the densest in Europe. The sapwood is typically cream-coloured and the heartwood has various shades of brown and purple. Lilac wood has traditionally been used for engraving, musical instruments, knife handles etc. When drying, the wood has a tendency to be encurved as a twisted material, and to split into narrow sticks.
Lilacs are often considered to symbolize love (see language of flowers). In Greece, Lebanon, and Cyprus, the lilac is strongly associated with Easter time because it flowers around that time; it is consequently called paschalia.
The Arnold Arboretum in Boston, Massachusetts, which celebrates "Lilac Sunday" every May. The Arboretum shows off its collection of over 422 lilac plants, of 194 different varieties. Lilac Sunday is the only day of the year when picnicking is allowed on the grounds of the Arboretum.
Lombard, Illinois, called the "Lilac Village", which has an annual lilac festival and parade in May. The village also contains Lilacia Park, a garden with over 200 varieties of lilacs, as well as over 50 kinds of tulips.
Rochester, New York, which has held its Lilac Festival since 1898, hosts the longest-running festival in North America. Held in Highland Park, this celebration features 1,200 shrubs, representing over 500 varieties, many of which were developed in Rochester. It is the largest collection of varieties at any single place.