Can I Cut Off Old Lilac Blooms From Last Year in Spring?

Pruning

• Lilacs are perennial shrubs that grow best in U.S. Department of Agriculture plant hardiness zones 3 through 7. Like many shrubs they benefit from a yearly pruning to remove any dead or damaged limbs and to maintain a pleasing shape. The best time to prune a lilac is in the late winter while the plant is still dormant, especially if there are many branches that need to be removed. While spent blossoms should be removed during annual pruning, it is not the only time they can be removed.

Deadheading

• Often pruning and deadheading are confused. Deadheading is simply removing old flowers and does not involve reshaping the plant or cutting back dead branches -- it's not necessary to wait until the winter months when a bush is dormant. To deadhead lilacs, follow the central stem of the flower down to the base where it joins the stem of the bush. Cut the flower stem just before it meets the branch.

Optimal

• The best time to deadhead lilacs is in the spring as soon as the flowers fade. This prevents the plant from spending time and energy producing seeds. Instead, the bush will put its resources into producing more buds and flowers for the next spring. Dry petals often drop during winds and rain, which can be messy, so prompt deadheading also results in tidier gardens and more attractive bushes during the summer months when lilacs are not in bloom.

Acceptable

• Fortunately lilacs are forgiving plants. They will bloom each spring whether they are deadheaded or not, although not as abundantly. Old blossoms can be removed in the summer or fall without causing any damage to the lilac bush. However, waiting until later in the summer to remove spent blooms will not encourage additional flowering next spring. If the bush does not drop spent blossoms during winter storms and the bush is not pruned while dormant, old blossoms can still be removed the following spring or summer without damaging the lilac bush.