Identifying characteristics:
The common lilac is a large, vigorous, shrub or small tree of suckering
habit. The plant can reach 15 to 20 feet, with a spread of 6 to 12 feet.
The semi-glossy, deciduous leaves are
opposite, simple, heart-shaped, and 2 to 5 inches long. The margins are
smooth and the foliage shows no autumn color. The flowers
are borne mid-May to early June in 4- to 8-inch-long, upright, cone-shaped,
terminal (usually paired) clusters. The individual flowers are 4 petaled,
usually a light purple (lilac) color, and produce a heady, pleasant fragrance
superior to that of all other Syringa species. The fruit
is a smooth, flattened, 2-seeded, dehiscent capsule that persists on the
plant over winter. The ovoid buds are large and stout, with 3 to
5 pairs of green and brown scales.
Similar species:
Ecology:
Distribution: This species was one of the earliest European plants
to reach North America and was introduced to the US from southeastern Europe.
Habitat: Hardy from zone 3 to 7, this species prefers moist, cool climates and neutral soils supplemented with leaf mold and humus. A position in full sun is essential to prevent fungal diseases. The common lilac is especially susceptible to powdery mildew in wet seasons and in shady locations, but may also be attacked by other pests and diseases such as Botrytis blight and bacterial blight. They are also subject to infection by phytoplasmas.
Uses:
Horticulture: This species is cultivated primarily for its showy,
nostalgically fragrant flowers and is often found growing near old homesteads,
spreading out in clumps from root sprouts. The large size and the suckering
habit of this plant make it suitable only for the shrub border, for group
plantings, and for screening purposes. Some authors maintain that by pruning
away faded flowers, the vigor of the next year's blooms will be enhanced.
Older plants need to be revitalized by pruning after flowering. A vast range
of cultivars have originated from this species, including 'Avalanche,' with
large, white flowers, good fragrance, and an upright habit; 'Little Boy
Blue," with sky-blue flowers, good fragrance, and a compact, rounded
shape; and 'Arch McKean,' a reddish-purple flowered, non-suckering variety.
'Alba' is an older cultivar with pale green leaves, white flowers and a
slender, upright habit. 'Aurea' is an attractive cultivar with young leaves
emerging yellow, turning yellowish-green.
The Japanese tree lilac (Syringa reticulata) is also a common ISU campus planting. It becomes a small round-crowned tree up to 30 feet in height. Showy white flowers are produced in early summer and the fragrance is similar to that of a privet, which some find less than pleasant. This is possibly the most trouble-free syringa, as it is resistant to mildew, scale and borer. This species is hardy throughout Iowa and is very picturesque in the winter landscape, with its stiff, rugged-looking outline.
