Lilac shrubs (Syringa species) are beloved for their dense, fragrant clusters of flowers that signal the arrival of spring. Propagating lilacs offers a cost-effective way to expand a collection or preserve a favorite variety from an established bush. While lilacs can be started from seeds, the resulting plants may not be true to the parent and take many years to bloom. Therefore, vegetative propagation methods like dividing suckers or rooting stem cuttings are the far more reliable approach. Successfully starting a new lilac requires understanding the specific techniques and timing best suited for each method.
The Easiest Method: Dividing Suckers
Dividing the natural offsets, or suckers, that grow from the parent plant’s root system is the easiest method for obtaining a new lilac start. Suckers are genetically identical clones and represent the plant’s natural tendency to spread, making this method highly successful. This process is best performed during the plant’s dormant season, ideally in early spring before new growth begins or in late fall after the leaves have dropped.
To begin, select a healthy, young shoot that has emerged away from the main trunk and has its own small leaves. Use a sharp spade or trowel to dig around the chosen sucker, working outward from the stem to uncover the root connection to the parent plant. The goal is to trace the sucker back to the main root connecting it to the original bush.
Once the connection is clearly visible, use a sharp pruner or spade to cleanly sever the root connecting the sucker to the mother plant. Ensure the severed sucker has a sufficient mass of its own fine, fibrous roots attached, as these are necessary for water and nutrient uptake. If the sucker lacks its own roots, it may not survive the transplant, so choose shoots that are well-established a short distance from the main crown.
Propagating New Plants from Stem Cuttings
Rooting stem cuttings provides an alternative propagation route when a lilac variety is grafted or does not produce viable suckers. The timing of collection determines whether the material is softwood or hardwood. Softwood cuttings, taken in late spring or early summer after the shrub has finished blooming, generally have the highest success rate.
A successful softwood cutting should be 4 to 6 inches long, taken from a stem that is pliable but snaps when bent sharply. Prepare the cutting by removing all lower leaves, leaving only one or two pairs at the tip. Lightly scrape a thin strip of bark from the bottom inch of the stem to expose the cambium layer, then dip the prepared end into a rooting hormone.
The cuttings need a sterile, well-draining rooting medium, such as peat moss and perlite or vermiculite, and a high-humidity environment to prevent desiccation. Plant the cuttings deep enough so at least one or two leaf nodes are buried, as roots primarily form from these points. Place the container in bright, indirect light and maintain consistent moisture until new root growth has established, which can take several weeks.
Successfully Transplanting Your New Lilac Start
Once the separated sucker or rooted cutting has developed a root system, it is ready for permanent establishment in the garden. Lilacs require a location that receives a minimum of six hours of direct sunlight each day. While they tolerate a range of soils, they perform best in well-draining conditions and prefer a neutral to slightly alkaline soil pH.
The planting hole should be prepared to be twice as wide as the root ball but only as deep as the root ball itself. Ensure the root flare—the point where the roots meet the stem—remains visible at or just above the soil surface. Planting too deep can suffocate the roots and lead to decline.
After setting the new plant, backfill the hole with the existing soil, gently tamping it down, and water thoroughly to settle the soil. Keep the soil evenly moist but never saturated during the first growing season. Applying organic mulch helps retain moisture, but keep it a few inches away from the stem to prevent rot.