Culture
Easily grown in average, medium moisture, well-drained soil in full sun. Tolerates light shade, but best bloom is in full sun. Intolerant of full shade. Prefers moist, fertile, organically rich, slightly acidic to slightly alkaline soils with good drainage. Avoid soggy soils. Needs good air circulation. Prune as needed immediately after flowering. To the extent practicable, promptly remove faded flower panicles before seed set. Best grown in climates with cool summers and cold winters. Not recommended for planting in hot and humid Zones 8 and up where chilling requirements are difficult to meet leading to unreliable blooming. Promptly remove root suckers, particularly on grafted plants, to maintain plant appearance and prevent unwanted colonial spread. Propagate by cuttings in spring.
Noteworthy Characteristics
Syringa vulgaris, commonly known as common lilac, is an upright, multi-stemmed, suckering, deciduous shrub in the olive family that typically matures to 12-16’ (20’) tall with a spread to 8-12’ (15’) wide. It is native to open woodlands, rocky hills and scrubby areas in southeastern Europe, but has been widely cultivated throughout Europe (beginning in the late 1500s) and North America (brought over by colonists in the early 1600s). It is particularly noted for its mid to late spring (May) bloom of very fragrant, tubular, 4-lobed, lilac to purple flowers (each to 1/3” long) which bloom in large conical to narrow-pyramidal panicles (to 6-8” long). Flowers give way to loose clusters of smooth, brown, flattened, dehiscent seed capsules (each to 3/ 4” long) which persist into winter if not removed. Glaucous, opposite, pointed-ovate to heart-shaped leaves (2-5” long) are dark gray-green to blue green. No fall color. Bark is gray to gray-brown.
Numerous cultivars have been introduced over time in both single and double-flowered forms. Cultivars extend the range of available flower colors to include shades of white, cream, rose, magenta, pinkish-purple, lavender and purple.
Common lilac has few post-bloom ornamental features of note. Significant post-bloom limitations include often leggy shrub form, foliage depreciation from powdery mildew, non-showy fruits and absence of fall foliage color. These shrubs are in large part grown for their flowers and fragrance. It is the State flower of New Hampshire even though it is not native to the U.S.
Genus name comes from the Greek word syrinx meaning tube or pipe in reference to the pith-filled but easily-hollowed stems of some genus plants.
Specific epithet from Latin means common.
Stems of Syringa were once used for pipes. In the same vein, Syrax was a nymph from Greek mythology who was metamorphosed into a hollow willow reed in order to escape the amorous advances of Pan, god of the fields and forests, in further reference to the hollow stems of some genus plants.
'Wedgwood Blue' is a compact, upright, deciduous shrub which typically grows only to 4-6' tall. Soft lavender-blue, sweetly fragrant, single flowers are arranged in dense, arching, wisteria-like, terminal clusters (panicles) which cover this shrub in late April to early May (St. Louis). Unusual pink flower buds.
Problems
Powdery mildew frequently attacks in summer. It can seriously affect the appearance of the foliage (unsightly whitish-gray patches begin to develop on the leaves in summer), but generally does little permanent damage to the shrub. Consider planting cultivars which are resistant to powdery mildew. Common lilac is susceptible to a number of additional disease problems including blights, leaf spots, wilts, ring spot virus and honey fungus. Potential insect pests include scales, borers, leaf miners, thrips and caterpillars. Deer tend to avoid this plant.
Uses
A reliable spring-flowering shrub for cold winter landscapes. Excellent as a specimen/accent or in small groups. Shrub borders. Hedges or screens. Cottage gardens. Margins of woodland gardens. Good cut flower.