Lilacs (Syringa spp.) are beloved for their intoxicatingly fragrant, showy blossoms that herald the arrival of spring. These classic shrubs or small trees are a staple in many gardens, valued for their beauty and resilience. However, one common challenge faced by lilac owners is their tendency to produce abundant “suckers” – vigorous shoots that emerge from the base of the plant or directly from the roots. If left unchecked, these suckers can quickly transform a graceful, single-stemmed lilac into an unruly thicket, reducing air circulation, competing for nutrients, and often diminishing the shrub’s overall floral display.

Understanding why lilacs sucker and implementing effective control methods are essential for maintaining the health, shape, and flowering potential of your cherished lilac bushes. This guide will delve into the reasons behind sucker growth, provide practical strategies for managing them, and even discuss whether these opportunistic shoots can be repurposed for new plants.

Why Lilac Suckers Grow

The propensity of lilacs to produce suckers is a deeply ingrained characteristic tied to their natural growth habit and, for many cultivars, their grafting history.

  1. Natural Growth Habit: Many common lilac species, particularly the common lilac (Syringa vulgaris), naturally grow as multi-stemmed shrubs. They tend to form dense clumps by sending out new shoots from their root crowns. This is a survival mechanism that allows them to spread vegetatively and recover from damage.
  2. Grafting: A significant factor, especially for many named lilac cultivars, is that they are grafted onto a different rootstock. The desirable flowering variety (the scion) is joined to the root system of a hardier, more vigorous lilac species (the rootstock).
    • Rootstock Suckers: When suckers emerge from below the graft union (i.e., from the rootstock), they are genetically different from the intended plant. These rootstock suckers are often more vigorous and will eventually outcompete the desired scion, leading to a shrub with inferior flowers or an undesirable growth habit if not removed.
  3. Stress or Damage: Lilacs may produce more suckers when stressed, such as from:
    • Improper Pruning: Cutting back stems too hard or at the wrong time can stimulate sucker growth.
    • Environmental Stress: Drought, nutrient deficiency, or root damage can also trigger the plant’s instinct to send up new growth from the base as a survival response.
    • Mechanical Damage: Mowing too close to the base or other physical injury can prompt suckering.
  4. Age: Older, well-established lilac bushes tend to produce more suckers as part of their natural aging and regeneration process.

Top Methods to Control Lilac Suckers

Effective sucker control requires diligence and the right technique.

  1. Pruning at the Right Time and in the Right Way:
    • Timing: The best time to remove suckers is as soon as you notice them, regardless of the season. The younger and smaller they are, the easier they are to remove and the less energy the plant wastes on them.
    • Technique:
      • Hand-Pulling (for very young suckers): If suckers are very small and tender, you might be able to simply pull them off by hand.
      • Cut Below Ground Level: For more established suckers, use sharp bypass pruners or loppers. Cut the sucker off as far below the soil line as possible, right where it originates from the root or stem. Cutting above ground level often stimulates more suckers to grow from the remaining stub. You may need to gently scrape away some soil to reach the base.
      • Avoid Shearing: Do not use hedge shears to trim suckers; this will only encourage more prolific and bushy growth.
    • Frequency: Be vigilant and check your lilacs for suckers every few weeks during the growing season.
  2. Chemical Control (Use with Caution):
    • Targeted Herbicide Application: For persistent or numerous suckers, a very targeted application of a systemic herbicide (like glyphosate, diluted according to product instructions) can be used.
    • Method: Cut the sucker off and immediately (within minutes) paint the freshly cut surface with a small amount of concentrated herbicide using a small brush or cotton swab. This allows the herbicide to be absorbed and translocated into the root system, killing the source of the sucker.
    • Pros: Can be effective at preventing regrowth from that specific point.
    • Cons: Non-selective herbicides like glyphosate will kill any plant tissue they contact, including the main lilac plant if misapplied. Use with extreme caution and only as a last resort. Always wear appropriate personal protective equipment (PPE).
  3. Root Collar Excavation:
    • Method: For heavily suckering plants, or to identify if suckers are coming from the rootstock, gently excavate the soil around the base of the plant to expose the root collar and upper roots. This allows you to identify where suckers originate and remove them cleanly from their point of origin.
    • Benefit: Ensures you’re cutting suckers correctly and can help you distinguish between suckers from the scion (which might be desirable for rejuvenation) and suckers from the rootstock (always remove).
  4. Maintain Plant Health:
    • Proper Pruning: Follow a regular pruning schedule for the main lilac bush, including rejuvenation pruning for older plants. A well-pruned, healthy plant is less likely to produce excessive stress-induced suckers.
    • Adequate Water & Nutrients: Ensure your lilac receives appropriate watering (especially during dry spells) and balanced nutrients. A healthy plant is more resilient.

Can You Replant Lilac Suckers?

Yes, you can often replant lilac suckers, but with important caveats.

  • For Own-Rooted Lilacs: If your lilac is an “own-rooted” variety (meaning it was grown from a cutting or tissue culture and is not grafted), then any suckers that arise will be genetically identical to the parent plant. These suckers can be carefully dug up with some roots attached and transplanted to create new lilac bushes.
  • For Grafted Lilacs: If your lilac is a grafted cultivar (most named varieties are), then the suckers coming from below the graft union are from the rootstock, not the desired flowering variety. These suckers will produce different, often inferior, flowers and growth habit compared to the main plant. Do not replant these suckers if you want a plant true to the original cultivar.
  • How to Distinguish Grafted vs. Own-Rooted:
    • Graft Union: Look for a swollen or knobby area at the base of the main stem, just above the soil line. This is the graft union. Any shoots originating below this point are rootstock suckers.
    • Uniformity: If all suckers look exactly like the main plant and produce identical flowers, it’s likely own-rooted. If suckers show different leaf shapes, growth habits, or eventually different, often purplish-pink, single flowers compared to the main plant’s double or unique blooms, they are likely from a grafted rootstock.

Steps for Replanting (Own-Rooted Suckers):

  1. Identify Own-Rooted Sucker: Ensure the sucker is coming from the main plant’s root system, not below a graft.
  2. Dig Carefully: In late fall or early spring, carefully dig around the chosen sucker, trying to get as much of its root system as possible. Use a sharp spade to sever its connection to the main plant.
  3. Prepare Site/Pot: Plant immediately in a prepared spot in the garden or in a pot with well-draining soil.
  4. Water In: Water thoroughly after planting.
  5. Patience: The transplanted sucker may take a year or two to fully establish and begin vigorous growth.

Alternative Plants to Lilacs

If the constant battle with suckers or the specific growing conditions are a concern, consider these alternatives that offer similar aesthetic qualities without the invasive suckering habit:

  • For Fragrance & Spring Blooms:
    • Mock Orange (Philadelphus spp.): Many varieties offer intensely fragrant white flowers in late spring/early summer. Generally non-suckering.
    • Viburnums (Viburnum spp.): Many species offer fragrant spring flowers (e.g., Koreanspice Viburnum, Burkwood Viburnum) and often attractive berries and fall foliage. Most are non-suckering or only mildly so.
  • For Showy Shrub Blooms:
    • Weigela (Weigela florida): Colorful, trumpet-shaped flowers in spring/early summer. Available in many sizes and leaf colors. Generally non-suckering.
    • Deutzia (Deutzia spp.): Arching branches covered in white or pink flowers in late spring. Many compact varieties.
  • For Pollinator-Friendly Shrubs (without suckering):
    • Ninebark (Physocarpus opulifolius): Native shrub with attractive foliage, flowers, and interesting bark.
    • Buttonbush (Cephalanthus occidentalis): Unique spherical flowers that attract a wide range of pollinators. Prefers moist areas.

Final Thoughts

Lilacs, with their irresistible fragrance and charming blooms, are truly a highlight of the spring garden. While their tendency to produce suckers can be a minor annoyance, it is a manageable trait. By understanding the reasons behind sucker growth – whether it’s their natural habit, grafting, or plant stress – and implementing consistent, proper pruning techniques, you can effectively control these unwanted shoots. Regular vigilance and the right approach will ensure your lilac remains a healthy, well-shaped, and abundantly flowering specimen, continuing to grace your garden with its timeless beauty year after year.