Lilacs (Syringa spp.) look delicate, but they can be an excellent wind and sound barrier. Their lovely, fragrant blooms and dense foliage make them an excellent choice for an informal hedge. Lilac hedges need good air circulation, so only plant them in a single row. Depending on the variety, lilacs may reach from 3 to 30 feet tall. Medium-sized lilacs such as dwarf Korean lilac (Syringa meyeri "Palibin") make the best hedges. Hardy to U.S. Department of Agriculture plant hardiness zones 3 through 7, dwarf Korean lilac grows 3 to 7 feet tall, and 5 to 7 feet wide.
Select an area that receives at least six hours of sun per day and has well-drained, neutral to slightly alkaline soil. Bare-root lilacs have to be planted immediately, while containerized lilacs may be planted whenever convenient. The best time to plant lilacs is in the fall before the ground freezes, but they may also be planted while they're still dormant in the spring.
Dig a hole slightly bigger than the size of the root ball. The roots should be able to spread out in the hole without bending. Set the lilac in the hole, making sure it sits 2 inches deeper than it grew in the nursery.
Add some soil around the roots, and water it. Wait until the water drains, then fill the hole to ground level with soil.Tamp the soil around the base of the lilac, and water it until it is evenly moist.
Apply a 3- to 4-inch layer of mulch, such as shredded bark, leaf mold or composted wood chips, in a ring around the lilac. Pull the mulch back 1 to 2 inches from the base of the plant. Space your other lilacs at 3- to 6-foot intervals, depending on the variety. As a general rule, spacing of lilacs should be at least half their mature width. For example, if your lilacs will grow to be 5 feet (60 inches) wide, space them 30 inches apart.
Water lilacs two to three times per week during the first month. If they do not receive at least 1 inch of water per week from rainfall after the first month, water them.
Apply a balanced, slow-release granular fertilizer over the root zone about one month after planting if the soil is not nutrient-rich.