Lilac shoots, commonly known as suckers, are vigorous upright stems that emerge from the roots or the base of the main plant. Lilacs, particularly the common varieties, naturally spread and rejuvenate themselves by sending out these new growths from their expansive root system. While this habit is how the shrub perpetuates itself, it often results in an ever-widening thicket that can overwhelm garden spaces and lawn areas. Managing these unwanted shoots requires a focused approach, moving beyond simple pruning to address the root connection directly.
Immediate Mechanical Removal Techniques
The most straightforward method for eliminating existing lilac shoots is mechanical removal, which avoids the use of chemicals. Simply cutting the stem at ground level will typically stimulate the plant to produce more, denser growth from the severed point, as the plant treats the cut as an injury and attempts to heal and regrow immediately.
To effectively remove a sucker, trace the shoot back to its point of origin, either on a main root or the trunk’s base. Gently scrape away the soil to expose this junction, then use sharp, sterilized tools, such as hand pruners or a sharp spade, to sever the sucker as close to the parent root or trunk as possible, ideally below the soil line. For small, young shoots, tearing or pulling them away from the parent root can sometimes be more effective than a clean cut, as this may remove the dormant bud tissue that causes regrowth.
While impractical for a large, established lilac, the most complete mechanical solution involves physically digging out the entire root crown and all connected lateral roots. Since lilacs can resprout from any remaining root fragment, this process is generally only feasible for small, young shrubs or when the entire plant is being removed. For mature plants, repeated, aggressive removal of suckers as soon as they appear remains the most practical non-chemical control.
Chemical Treatment Options for Persistent Shoots
When mechanical removal fails and suckers continue to emerge aggressively, a targeted chemical treatment may become necessary. This approach is reserved for persistent shoots, particularly those growing far from the parent plant where they can be treated without risking the main shrub. Systemic herbicides, such as those containing glyphosate or triclopyr, are the most effective choice because they are absorbed by the plant and translocated down into the root system.
A highly specific and safe application method is the “cut-and-paint” technique. For this, you first cut the sucker stem cleanly a few inches above the ground. Immediately after cutting, before the plant tissue begins to seal, use a small brush to apply a concentrated, undiluted systemic herbicide only to the fresh cut surface. This method minimizes the risk of the chemical drifting onto the parent lilac or surrounding desirable plants, ensuring the herbicide is absorbed directly into the sucker’s vascular system.
The optimal time for this application is in the late summer or early fall, which aligns with the perennial plant’s natural cycle of transporting nutrients down to the roots for winter storage. This downward flow carries the systemic herbicide directly to the root system, maximizing its effectiveness. Always wear appropriate personal protective equipment (PPE), such as gloves and eye protection, and follow the specific instructions on the herbicide label.
Strategies for Long-Term Suppression
Long-term control of lilac suckers requires addressing the underlying reasons why the plant produces them. Suckering is often a response to stress or physical damage to the roots, which triggers dormant buds along the root system to sprout. Therefore, avoiding root injury is paramount; exercise caution when cultivating, weeding, or mowing around the base of the lilac.
Applying a thick layer of organic mulch, such as wood chips, around the base of the lilac can help suppress surface shoots and maintain consistent soil moisture, which reduces plant stress. The mulch should be spread a few inches deep, but kept a short distance away from the main trunk to prevent moisture buildup and potential rot. For grafted lilacs, suckers emerging below the graft union must be removed, as they originate from the rootstock and can eventually overtake the desired top growth.
If the lilac is growing on its own roots, the suckers are clones of the main plant and will flower with the same characteristics, meaning you can choose to leave a few to rejuvenate the shrub. Newer lilac cultivars, particularly those in the Syringa meyeri or Syringa microphylla groups, are specifically bred to be less prone to suckering than the common Syringa vulgaris. Selecting one of these non-suckering varieties for future plantings can solve the problem entirely.