Lilacs are a hardy shrub that are relatively easy to grow and can reach heights anywhere from 4 to 30 feet, depending on the type of bush. Their large flowers typically bloom in the spring with a color range including pink, purple, blue-lavender and white, and an intoxicating fragrance. Over 1,000 varieties of lilacs are available, and by planting bushes that bloom at varying times, you can ensure a continuous showcase of flowers for about 6 weeks.
Grow your lilacs in a south or southwest facing area where they will get at least 6 hours of sunlight daily. Do not plant lilacs near walls or large growing trees, which can create conditions that are too shady for the bush to thrive. The amount of blooms, the intensity of the colors and how tall the bush grows are all dependent on receiving plenty of sunlight.
Water lilacs infrequently yet thoroughly, especially during the summer months, when they can become too dry. Using a soaker hose is best for watering deeply and letting it run for around an hour a week. Water two times a week in hotter months or if the leaves become droopy, which is a sign that it is drying out too much. Be sure the soil is well draining since lilacs can die if the soil becomes too soggy. Compost or peat moss worked into the soil before planting often resolves this situation.
Add mulch around your plants to hold in moisture and keep the soil cool. In early spring apply a layer of compost around the base of the plant, followed by a 2-inch-thick layer of mulch such as shredded bark.
Fertilize your lilac in early spring before flowering begins. Use a general flower fertilizer that is higher in phosphorous and potassium to encourage more blooms (e.g. 5-10-10). Apply another application of fertilizer after the leaves have fallen off, usually in late fall. Follow the directions on the fertilizer for how much to apply.
Deadhead the spent flowers as soon as they fade to encourage more abundant blooms. Cut the dead flowers off right below the individual flower head. An overall pruning is not required for lilacs, but can be done if the bush is becoming too tall and not producing many blooms.
To prune, cut back one-third of all the main stems that at least 1 1/2 inches in diameter, cutting to about one foot from the ground. If pruning your lilac bush, do so immediately after it stops blooming usually in early to late summer.