Lilac Bushes: Growing Tips

Pruning, Other Care Advice for a Fragrant Wonder Shrub

Lilacs (image) are big, beautiful, fragrant. The purple flowers bloom in May.
Big, beautiful, fragrant -- what more could you ask of the flowers of common lilacs?. David Beaulieu

How Lilac Bushes Are Classified

Plant taxonomy classifies common lilac bushes as Syringa vulgaris. An example of a cultivar of this plant is 'Wedgewood Blue.' Mention of these plants almost surely does not evoke thoughts of the extra virgin olive oil you find so essential when you cook Italian meals, yet Syringa is, in fact, a member of the olive family, along with other such ornamental plants as ash trees, forsythia shrubs, and privet shrubs.

Most kinds are deciduous shrubs. 'Wedgewood Blue' is one variety that has a compact growth habit. But because of the height some varieties attain at maturity, people sometimes refer to them as "lilac trees," lumping them in with the other wonderful flowering trees of spring. These plants should not, however, be confused with the true "tree lilacs," that is, Japanese tree lilacs (Syringa reticulata) and Chinese tree lilacs (Syringa pekinensis).

True "tree lilacs" (Syringa reticulata and Syringa pekinensis) bloom a bit later than lilac bushes. Their blooms are white, and they are not as aromatic as the flowers of common lilac bushes. But the tree lilacs do have an attractive bark, especially the Chinese tree lilac, which has a shedding bark similar to that of the paper birch.

Profile of a Fragrant Shrub

'Wedgewood Blue' attains a height at maturity of only 6 feet, with a spread equal to that.

But the species plant can grow to be anywhere from 8 to 20 feet high. Flower color for 'Wedgewood Blue' is lavender-blue, and the flowers are contained in thick clusters. But other types come in a variety of different colors, such as:

  1. White.
  2. Reddish purple.
  3. Pink.
  4. Magenta.
  5. Bicolored.
  6. Deep purple.
  7. And, of course, the namesake color, "lilac" (light purple).

    Blooming time is late spring. The leaves are dark green, but this shrub is grown first and foremost for the fragrance of its flowers and their beauty, not its foliage. The smell of their blossoms is one of the most unforgettable aromas of the plant world.

    It is beyond dispute that the outstanding quality of many of these plants is the smell of their flowers (we can only say "many," not "all," because not all types are equally fragrant; grow Syringa vulgaris when in doubt if smell is your main interest). They are among the most fragrant flowers available to gardeners in cold climates. If you grew up smelling them every year as spring begins to yield to the warm nights of summer, then you are probably spoiled for life.

    Growing Tips: Planting, Care (Pruning, Etc.)

    The climate is most favorable for growing these flowering shrubs in USDA plant hardiness zones 3-7.

    Grow lilac bushes in full sun. They prefer a rich, well-drained, loamy soil with a neutral soil pH, but they will still grow in clay soil (just not as well). These wonderful bushes are, unhappily, prone to powdery mildew disease, so provide good air circulation by keeping their branches pruned.

    The right time to prune is just after blooming is over, since these are shrubs that bloom on old wood.

    Branch pruning is done to thin out the growth (for better air circulation) and to keep the height of the plants in check. In addition, cut the dead flowers off when they are done blooming. This will prevent the seed from forming and thereby promote more profuse flowering the next spring.

    Read this care tip if your lilacs are not flowering. Another problem growers frequently have with common lilacs is that they become too big as the years go by. This happens when you (and/or the prior landowner) have failed to stay ahead of their growth by pruning them. But the problem is fixable: Here is how to trim overgrown lilacs, which will also help rejuvenate them.

    Uses in Landscape Design

    Common lilac bushes are attractive enough to be treated as specimens. They are also often planted in rows along property borders and pruned into loose hedges.

    Other kinds of lilac bushes exist, too, in addition to the common type covered above. The 'Miss Kim' cultivar (see below) is small enough for use in foundation plantings, as is the even more compact Bloomerang lilac, which is a dwarf shrub. Sound interesting? Here are the facts about Bloomerang.

    Bloomerang Lilacs Are Compact, Bloom Profusely, Boomerang Back With Fall Flowers

    Below, this plant, technically known as Syringa x 'Penda' Bloomerang®, will be referred to simply as Bloomerang lilac, as most people use the trademark name as the common name. 'Penda' is the true cultivar name. The plant is classified by horticulturists as a hybrid, deciduous shrub. 

    Bloomerang tops out at 5 feet tall at maturity (at the very most), with a similar spread. It usually stays smaller than this (and can easily be kept smaller by pruning). Compared to common lilac (that is, the Syringa vulgaris discussed above), it is thus quite compact, which is why it is considered a dwarf lilac.

    The flower color is a light purple. Flowers come in terminal clusters, as on common lilac shrubs. Do not expect younger plants to have as many flowers as older plants will. Like Syringa vulgaris, Bloomerang lilac is one of the plants with fragrant flowers, although most growers prefer the fragrance of the former. The leaves are dainty, being much smaller than those on common lilacs.

    The shrub blooms initially -- and most profusely -- in May in a zone-5 landscape, for example. But it received its name because of the ability of its blooms to come back again (like a boomerang) during the summer and fall (albeit more sparsely). If you are in the habit of planting fall flowers such as chrysanthemums and late annuals to jazz up your autumn landscaping and would like to supplement these with flowering shrubs, Bloomerang lilacs are a good choice.

    Gardeners in planting zones 4-7 can grow Bloomerang lilacs. Choose a location with good drainage and full sun. A loamy soil fortified with compost (or a slow-release fertilizer if you do not use compost) is optimal.

    Prune Bloomerang to shape it (as desired) immediately after blossoming is over in spring. The bush blooms on both old and new wood: The May flowers spring from old wood, while the reblooming will occur on new wood (which is why you do not want to prune too late). If you do not prune, at least deadhead; this will foster additional reblooming.

    There are two plant-care tasks you do not have to worry about with Bloomerang lilacs:

    1. They are mildew-resistant, unlike common lilacs.
    2. They are deer-resistant shrubs.

    Lilacs make wonderful cut flowers (the larger flower heads from the common lilac are best, but Bloomerang's blooms are still quite worthy of cutting). With a bush that bears as many blooms as a mature Bloomerang lilac, you should have no qualms about snipping off a few blossoms and bringing them indoors to show off in a vase. In terms of outdoor uses, the following come to mind:

    1. As a hedge plant for the summertime yard
    2. To attract butterflies 
    3. As a spring specimen plant
    4. It's small enough to plant around a patio
    5. To draw hummingbirds

    Comparison of Dwarf Lilac Bushes: Bloomerang vs. Miss Kim

    'Miss Kim' lilac is another type of dwarf lilac bush that is widely grown in North America. It has the potential to get bigger than Bloomerang, which counts as a demerit against it (if you are landscaping in a small yard). There are some other ways in which the two shrubs differ, as well. Miss Kim:

    1. May not bloom as profusely as does Bloomerang
    2. Has a coarser plant texture
    3. Offers a bit of fall foliage interest (Bloomerang does not)

    Return to Late Spring Blooming Shrubs