If you were deaf, dumb, and blind you could still love lilacs. The rich distinctive perfume is beloved by gardeners in every region they're grown.
Lilacs are a deciduous shrub and bloom from March to May in most North American gardens. They are hardy in zones 3–7, generally preferring cold winters, but there are varieties that do well in somewhat warmer climates.
Sun is a primary requirement for lilacs. While they can take partial shade, too much makes them leggy and sickly looking. They are adaptable as to soil type and moisture, however, which makes them a good choice for many gardens.
They range in color from white to dark purple with a full range of pinks, mauve, and blue-violet, to wine red and deep amethyst. There are even a few yellow lilacs. They have cascading clusters of tiny single and double flowers amid deep green heart-shaped leaves. They are typically large at maturity from about 8–20 feet tall and about 10 feet around.
Lilacs make beautiful hedges, serve as effective windbreaks, and make distinctive accents. There are literally hundreds of varieties from the small and dainty pink 'Fairy Dust' lilac to the old-fashioned syringa vulgaris. The range of varieties guarantees that there is a perfect lilac for every gardener.
As mentioned, siting your lilacs for sun is a basic requirement. They are adaptable concerning soil, but in more acid soils they benefit from adding a bit of lime every couple years.
Planting in the fall will give your lilac a chance to settle in before going dormant, though you can plant in the spring as well.
Propagate new plants from the suckers that your lilac produces at the base of the main stem. It's much easier than from cuttings.
Some varieties are susceptible to powdery mildew, but others like the 'Madame Lemoine' (white) and 'Charles Joly' (violet red) are resistant. Pruning old and dead wood will prevent other pests like borers from becoming a problem.
Lilacs should receive their annual pruning immediately after the flowers have faded. With a pair of sharp pruning shears cut any sucker growth off close to the ground and remove any ill-placed branches.
Prune out dead branches, remove about one-third of the old branches to promote vigor, and shape your plant. Next year's blooms are produced on new buds that develop immediately after this year's bloom. Heavy pruning can reduce next year's flower production, so be careful.
Lilacs can get very tall and it's a good idea to keep them in the 8–10 foot range for manageability.
Old lilacs that have been neglected can look ratty and ugly. To renew them, you have a choice of the love-it-and-leave-it method or the more systematic approach. The first approach requires pruning the plant back to about a foot in March, which will force the development of new branches. The next year, in January or February, prune back to the ground all but several of the healthiest new branches. The new healthy branches upon which you are pinning your hopes should be cut back to just above the buds. This will force branching and create a nice shape. The following year, you should have a decent looking shrub.
The second approach to renewing an old lilac is to cut back to the ground one third of the old growth in each of three successive years until all the old wood is replaced. Continue to do thinning and maintenance pruning, but within a few years, your rejuvenated lilac should be restored to it's natural beauty.
Lilacs: The Genus Syringa--Probably the only book you'll ever need for your lilacs.
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