Plant 12 feet apart in a sunny location and in a site where good air circulation is available. Lilacs are widely tolerant of soils, but prefer good drainage and a nearly neutral soil, supplemented with organic matter. Lilacs will benefit from light shade during the afternoon hours in southern areas. Some of the S.vulgaris hybrids also are tolerant of pollution.
Because they are shallow rooted, mulching rather than cultivating around the plant, is recommended. Yearly applications of 5-10-5 fertilizer and bone meal, both applied in early spring will promote flowering. Remove spent flower clusters and prune after flowering to keep center open to sunlight. Remove suckers(growth from the base), and prune out some of the older wood periodically to renew the plant.
If Oyster Shell Scale, Lilac Borer, or mildew are a problem, spraying at the first sign of these troubles will control them. In some rare instances, where mature Lilacs prove reluctant to flower, root pruning may encourage flower production. This is done by using a spade to cut down into the soil around the plant at the drip line of the branches. Old plantings may be rejuvenated by cutting back all old growth to ground level in early spring and allowing new vigorous growth to replace it.