The sweet smell of Syringa bushes, commonly called lilac, permeates the air from spring to early summer, depending on the variety of lilac you grow. These deciduous shrubs grow in full sun or partial shade in shades of white, yellow, purple, pink and lavender. Many species grow in U.S. Department of Agriculture plant hardiness zones 3 through 9. The old-fashioned types grow in the cooler regions, but the hybrid Chinese lilac (Syringa chinensis) does well in the warmer regions. No part of the lilac bush is toxic, so it is a safe plant. Propagation is done through cuttings, layering or off-shoots.
Rooting Lilac Cuttings
Lilac cuttings root best when taken during the late spring or just after the bush stops flowering. The wood is considered softwood, which means it is still green but firm. Use a rooting medium that's equal parts coarse sand, peat moss and perlite and dampen it before putting it in the pot. Remove all but the top two leaves on the cutting, coat the bottom with the hormone and stick the cutting into the rooting medium. A rooting hormone on the bottom 3 inches of the cutting helps encourage rooting. Cover the container with a clear plastic bag and set in a bright spot. Remove the plastic daily for about an hour. The cuttings will root in four to six weeks.
You can air layer or soil layer a lilac stem to produce another plant. Layering means a stem is wounded and dressed so the damaged area produces roots. Once the roots develop, you can sever the upper portion, just below the new root ball, and transplant the new lilac bush into the garden. To air layer the stem, remove only the outer bark from a portion of healthy stem so the cambium layer is exposed. Wrap the wound in moist sphagnum moss and seal the entire area with clear plastic that is secured at the top and bottom of the moss. Once you see roots growing in the moss, it is time to sever the new plant.
To soil layer, pull a low-growing stem to the soil surface and wound the section of the stem that touches the soil. Bury the wounded section in a trench, with the leaf end coming out the other end of the trench. Sever the new plant from the mother plant the following spring.
Lilac shrubs produce new shoots, called suckers, at the base of the parent plant. These suckers grow from the main root system and can survive on their own when they reach about 6 to 12 inches tall. Carefully dig the sucker so you bring as many roots as you can with it. The sucker may be attached to the main root system so you must cut the shoot from the parent plant. Transplant the sucker where you want it in the garden. Keep the new plant watered well until it becomes established.
Many lilac bushes sold at garden centers are grafted onto rootstock that is less susceptible to disease or pest infestations. This means the lilac you buy has one type of lilac for the roots and another for the stems, leaves, branches and flowers. The cuttings taken from grafted shrubs may be a different size than your lilac. The same is true of the plants propagated through layering. If you dig up suckers from the parent shrub, the suckers may produce a different color bloom than the lilac you are growing.