A lilac bush does best when it is trimmed every year.

Apr 06, When To Prune. As a general rule for all lilacs, they should be pruned immediately after they’re done flowering in the spring. Since lilacs set next year’s flower buds right after the current year’s flowers have faded, pruning later in the summer or fall will result in Estimated Reading Time: 4 mins.

If you want to prune your lilac to reshape it or to reduce its height, you could do it now, but it would be better to wait until spring.

Jun 09, Courtesy Jean Owens Eastern tiger swallowtail butterfly on a lilac bush. Lilacs are popular shrubs for their fragrant colorful blooms. Many gardeners wonder exactly how and when to prune lilacs. Ken Kuhnen of Machesney Park, Illinois, wrote in asking, “My lilac tree is beautifully shaped, but I need it to be shrubmulching.barg: maryland.

A lilac bush does best when it is trimmed every year. Doing so helps to maintain the plant's shape and to minimize the number of old, damaged branches, which are vulnerable to disease. An older Missing: maryland. Apr 27, Cut back 1/3 of the older lilac canes or branches. The following year cut out the next 1/3 of the oldest branches then the final year cut back the last of the oldest branches.

Doing this in 1/3’s will let you have blooms and still cut back the old worn out branches fully renovating the shrubmulching.bars: Aug 21, For lilac, that can be a few years. For hydrangeas and forsythia, it might be only three years, or even two years for a vigorous plant.

Also when trimming the old blooms, cut back about a few inches on the branch to rid the area that has lack of nutrients to the bloom.

Abelia is more variable. Stems bloom less and become more gnarly as they age.

I prefer to prune all such plants while bare in shrubmulching.barg: maryland.