Lilacs are low-maintenance, easy to grow, and are very hardy plants. They offer good summer shade once they have reached their mature height, and do provide privacy from the neighbors! The average size for a lilac bush is approximately 10 feet (3.04 m). Tackling the job of trimming, shaping, and pruning lilacs is easiest when you know how. Pruning should be done immediately after the flowers have died off. With a little pruning knowledge and how to replenish the old wood with new shoots, the shrubs can last a lifetime.
Plan to prune your lilacs at the end of the bloom season, which occurs in early summer. Pruning too late will result in a reduction of blooms in the next season. Pruning too early will lessen the amount of time you have to enjoy your bush or lilac treeduring the season.
You will need pruning shears, a small saw and gardening gloves.
Decide on the lilac bush height: Prune fewer old stems at the top of the bush if you prefer tall bushes. Since the older stems produce the flowers, trimming too many of them will cause the lilac bush to have less flowers.
Clip off the dead flowers: Spent lilac flowers are primarily located at the top of the bush.
Trim shoots near the ground: Keeping the new shoots trimmed off ensures the bush will not become overgrown and cumbersome.
Reach into the bush and clip a few larger stems: This will allow more sunlight to reach the inside stems.
Prune dead or unhealthy-looking stems: These are stems that are broken, withered and often hanging haphazardly on the tree.
Trim branches: Focus on cutting the branches that stick the farthest out from the bush and any branches that are twisted around each other. Use the saw to cut the branches if your lilac plant is older and the branches are thick.
It is best to mulch two to four inches to maintain soil moisture and to keep weeds down. Add compost and humus that is worked into the soil to provide added nutrients and retain water during dry spells. Use a general-purpose fertilizer in early spring to promote blooming. Do not give too much nitrogen since this will result in too few blooms. After the lilac has stopped blooming, add some more general-purpose fertilizer. Lilacs do not like wet soil over a prolonged period of time. The roots run very deep, so if there is an extended drought period, water infrequently but thoroughly. They bloom best in full sun and prefer organically rich, slightly acidic soils with good drainage. With its lovely spring accent, it makes a wonderful screen or border specimen! Or try some of the new dwarf lilacs such as the Dwarf Korean Lilac.