Few garden plants herald in springtime like the sight and scent of lilacs. Unfortunately, the aggressive growth habits of lilac shrubs can make them an unwelcome shrub in the landscape. Simply cutting down a lilac won't keep the roots from sending out new shoots. Permanently removing an unwanted lilac requires a little extra effort.
Lilacs are deciduous shrubs that thrive in a variety of soils and climates. These hardy shrubs reach a mature size between 3 and 20 feet tall and produce masses of fragrant blossoms in the spring. Lilacs reproduce by both seed and sucker production. The roots of lilacs form lateral shoots that spread parallel with the surface of the soil, sending up new suckers that can grow into mature shrubs. Without proper control, single lilac plantings can spread to form small groves of shrubs.
The first step in removing a lilac is to cut down the exposed portions of the plant. Depending on the size and age of the shrub, a pair of sturdy pruning shears and a small limb saw can remove the above-ground vegetation, leaving small stumps near the surface of the soil.
Glyphosate is a chemical ingredient in many broad-spectrum herbicides. When applied to the open cuts on the lilac stumps, this chemical will penetrate into the living cells and begin killing the roots. The best time to apply glyphosate is within one hour after cutting the exposed growth. While applying the glyphosate to the pruned stumps, check the surrounding area for the appearance of small, thin suckers that also require treatment. The glyphosate needs at least 24 hours to begin working. Watering or rainfall before this time will rinse away the chemical and minimize its effectiveness.
To use the area for foot traffic or new plants, you must remove the main root ball and the exposed stumps. The best time to do this is after the stumps begin to turn black and wither. Soaking the soil around the roots about 24 hours before removal will help loosen the soil and make extraction easier. Digging a circular trench about 12 to 18 inches outside the edges of the exposed stump will allow you to remove the main root ball and the nearby suckers.