For a lot of us northern gardeners, lilacs are landscape essentials we can’t live without. Until their delicious fragrance permeates our yards and homes, spring is incomplete. Reliable and low-maintenance, lilacs can flourish for decades with very little care. By planting several types of lilacs, from early bloomers to late-blooming types, you can prolong your bloom party by several weeks. All it takes is good site selection, proper water and fertilizer, and timely pruning to keep lilacs at their blooming peak.
Selecting the Right Site
- full sun – Though some lilacs tolerate partial shade, all prefer at least six hours or more of daily sun. More sun translates to more, better blooms.
- good drainage – Lilacs don’t like wet feet, so avoid low spots where water collects. Plant your shrubs in areas where soil drains well instead.
- good air circulation – In crowded conditions, lilacs are more vulnerable to powdery mildew — that white dust sometimes seen on lilac leaves. Good air circulation discourages leaf diseases.
- near-neutral soil pH – Lilacs do best when soil pH isn’t too low or too high. Avoid planting in high-pH (alkaline) soil, which can cause nutrient deficiencies and yellow lilac leaves. If you’re unsure about your soil pH, your local extension agent can help.
Watering and Fertilizing Your Lilacs
Under normal weather conditions, mature lilacs thrive with whatever rain nature provides. But young, newly planted lilacs need extra care — it takes about six weeks before they establish new roots. Provide your lilacs with enough supplemental water so they receive 1 inch per week, from irrigation and rainfall combined. That’s roughly the same amount your lawn needs to stay healthy and green.
During periods of drought, it’s a good idea to treat established lilacs with regular watering, too. This is true for all types, from luxuriant French hybrids such Katherine Havemeyer and its purple-mauve double blooms to the dwarf tree-form Palibin lilac and its soft lilac-purple flowers. Stick a finger into the soil about 3 inches deep. If it’s dry, water the soil around the shrub thoroughly.
Established lilacs need very little fertilizer to stay healthy and nourished. Apply a balanced, complete fertilizer (like a 10-10-10) once in early spring, and that’s all you need. Avoid high-nitrogen fertilizers, which push green growth instead of blooms.
Pruning to Promote Prolific Blooms
Unless your lilacs are old and overgrown, keep pruning to a minimum. For general shaping, as with hydrangea pruning, timing is extremely important. For best results, prune all lilacs right after they finish blooming. The buds that become spring flowers develop during summer — if you wait too long, you’ll prune off the buds that become next spring’s blooms. If you grow several types of lilacs, wait until the late-blooming lilacs, like the two-toned pink Minuet, finish up in June. Then prune all your lovely lilacs at once.
If your old lilacs need rejuvenation, consider it a three-year project. Prune one-third of the oldest stems back to the ground in late winter or early spring. Then do the same thing, one-third at a time, the next two years. You’ll sacrifice blooms along the way, but the end result will be worth it. Remove dead or damaged branches any time.
With these simple basics, you can enjoy a lifetime of lilac-filled springs. Shop our plants online for home delivery almost anywhere in the continental United States. If you’re in the Madison area, stop in at Winterland Nursery, our retail garden center. We love to talk lilacs — or anything else plant-related. We look forward to seeing you there.