A lilac is often much bigger than the homeowner anticipated, and it can become overgrown and dominant in the landscape. Pruning a tree to artificially control its shape or size has mixed results, but selectively pruning the lilac to support the best flower display can also keep it from outstripping its own space.
Growth Habit of Lilac
The adult size of this lilac should be taken into account when you are making decisions regarding where to plant it. Varieties of this lilac (Syringa spp.) Species vary in size from 5 feet to 30 feet high, and usually the width is like the height. Generally, shrubs — such as lilacs — appear better if they have the environment and space to grow into their normal shape and size, but routinely pruning the lilac to get rid of less-productive old stems maintains it beneath its maximum dimension.
Stem Renewal and Pruning
Lilac flowers bloom prolifically on stems that are 1 to 2 inches thick as opposed to 3 inches thick or more. Once the lilac is 6 to 8 feet high, or about five years old, regular pruning to select stems of different ages and thicknesses maintains the lilac flowering around, and not simply the top. This type of pruning will keep the lilac at a consistent dimensions, whereas it may become much bigger without the focus.
Rejuvenating Overgrown Lilacs
Lilacs have a tendency to become overgrown and crowded when they age, especially if they’re not regularly pruned. Flowering is inhibited on the old branches, and the lilac total health is undermined. To replenish the lilac, cut one third of the largest stems, or trunks, to the bottom, repeating for three seasons. The size of this lilac is reduced, and resuming stem pruning will keep it from getting outsized and unwieldy again, in addition to improve the flower display.
Small and Manageable Lilacs
Among the approximately 2,000 lilac cultivars, many are compact in size, or dwarf varieties. Meyer lilacs (Syringa meyeri) and Manchurian lilacs (S. patula) possess a compact spread; “Miss Kim” grows 5 to 7 ft high. Chinese hybrids (Syringa x chinensis) don’t sucker up to common lilac, and they are more inclined to stay within bounds. Preston hybrids (S. reflexa x S. villosa) grow 10 to 12 feet high, but by pruning them to three to five trunks when they’re young, they can be formed into small trees.