Know which one you’ve got

Syringa vulgaris is the one in most old yards. It hails from the rocky hills of the Balkans, grows into a big suckering thicket and carries the classic fragrance. Hundreds of cultivars exist, single and double, from white through blue and pink to deep purple. Some colour outside the lines. ‘Sensation’ has purple petals edged in white, as if each flower had been carefully outlined. ‘Primrose’ is the yellow one, though its butter yellow often turns out to be more of a cream; plant it beside a white lilac and the yellow shows up better. Both came from the same Dutch nurseryman, who found them as chance mutations on other lilacs.

S. ×hyacinthiflora crosses S. vulgaris with a Chinese species and blooms a little earlier. Frank Skinner of Dropmore, Manitoba, bred many of the hardiest, with his first introductions in 1932. ‘Pocahontas’ and ‘Maiden’s Blush’, his last introduction, are still sold.

S. ×prestoniae is Canadian bred. Isabella Preston, Canada’s first female professional plant breeder, made the original crosses at the Central Experimental Farm in Ottawa in 1920, using two very hardy Chinese species. The results are big, fast shrubs with nodding clusters in pinks and lavenders and a spicier scent. They bloom about 10 days after S. vulgaris, which stretches the lilac season nicely. Many are named for Shakespeare characters, so a Preston hedge reads a bit like a cast list.

S. meyeri ‘Palibin’ is the classic choice for small yards. It stays around 4 to 5 feet and suckers very little. S. pubescens subsp. patula ‘Miss Kim’ is often sold as a dwarf too, but give it time and it reaches 6 to 8 feet. It just takes its sweet time getting there. For a truly small lilac, ‘Baby Kim’ stays at 2 to 3 feet and keeps its purple colour instead of fading to white.

Reblooming lilacs, such as the Bloomerang series, ‘Josee’ and ‘Scent and Sensibility’, flower in spring, take a rest, then bloom again from midsummer into fall on the season’s new growth. The encore is lighter than the main show and depends on a cool summer, so think of it as a bonus. These are compact plants, mostly 3 to 6 feet.

Planting

Give lilacs sun. In shade they grow tall and gangly, reaching for light, and bloom sparsely. They want well-drained soil and dislike wet feet, but they’re happy in the alkaline soils found across much of Canada.

Buy own-root plants when you can. Suckers from an own-root lilac are the same plant, so you can dig them up and share them. Suckers from a grafted lilac come from the rootstock, which may be a different lilac altogether, and they can quietly take over.

Nurseries graft lilacs because they’re surprisingly hard to root from cuttings, but tissue culture has made own-root plants much easier to find. If you do buy a grafted lilac, plant it with the graft a few inches below the soil so the top can grow roots of its own.

Prune after the party

Lilacs set next year’s flower buds in summer, a few weeks after bloom ends. The buds sit through winter already formed and finish developing in spring. Prune right after flowering. A tidy-up in fall or early spring removes exactly the flowers you’ve been waiting for.

Deadheading is just the lightest kind of pruning, and it follows the same rule. If you want a tidier shrub, snip off the spent clusters right after bloom, cutting just below the flowers so you leave the new shoots underneath alone. Skip it and the lilac won’t mind. Larry Hodgson, Canada’s Laidback Gardener, called deadheading lilacs a garden myth and said it changes nothing. He argued most S. vulgaris cultivars tend to bloom heavily one year and lightly the next regardless.

On rebloomers, trimming after the spring flush delays the second round by a few weeks.

Old lilacs get tall, with every flower at the top. After bloom, cut a third of the oldest, thickest stems to the ground, and keep a few strong suckers as replacements. In three years you have a new shrub on old roots.