Things You'll Need
Lilac (Syringa) is a diverse group of flowering shrubs in the olive family of plants. The hundreds of varieties of lilac offer a wide range of sizes, shapes and colors -- from pure white to deep purple. Lilacs are a staple in home gardens because they are hardy, require little care and produce fragrant, attractive flowers in most years. To produce flowers, however, lilacs need cold winters and a small amount of maintenance while the shrub is dormant.
Clip off any remaining spent flowers as the plant prepares to go dormant for winter.
Feed lilac bushes with lime fertilizer during the winter to provide it with the nutrients it needs to thrive; lilac bushes prefer a slightly alkaline soil. Apply a second feeding of lime fertilizer after the lilac blooms in the spring.
Prune back one-third of the oldest branches as far as you can in winter. This encourages the plant to sprout new limbs. Pruning also maximizes the number of flowers and keeps the shrub in an attractive shape.
Cut old lilac bushes to the ground in winter; as lilacs mature, the lower portions of the plant become shaded and loose their vitality. Trim the entire plant to within six to eight inches of the ground, using garden shears or a small saw. It will take a few years for your lilac bush to return to its former appearance, but then it will produce an abundance of flowers.
As with other flowering plants, the best way to keep your lilac bush healthy and productive is to prune right after flowering so that you know exactly where next year's flowers will sprout.