How To Grow and Care for Lilac Bushes
What sweet-smelling harbinger of spring was introduced into American gardens in the 18th century, and is still popular in them today? Lilacs!
Lilacs have a long, lovely history in American gardens. Their scent takes us back to the heirloom varieties in our grandparents’ gardens, or perhaps triggers memories of that famous Walt Whitman poem written in the spring of 1865, following President Lincoln’s assassination: When Lilacs Last in the Dooryard Bloom’d.
Each spring, lilacs are celebrated in annual festivals across the country, from Rochester, New York, to Mackinac Island, Michigan, to Spokane, Washington. Welcoming one into your yard qualifies as carrying on an American tradition.
Read on to learn how to plant and nurture your own lilac bush or tree.
When To Plant Lilacs
The best time to plant lilacs is in the fall after they’ve dropped their leaves. This gives them a chance to grow strong roots before spring, with less watering required.
Most of us will be tempted to buy lilacs in the spring, when we see them in bloom at the garden centers. It’s fine to buy them when you can see and smell the flowers and know what you’re getting. Just remember to keep them well-watered throughout the summer.
Where To Plant Lilacs
Lilacs have a few simple requirements that will ensure you get as many blooms as possible to enjoy each spring.
Lilacs prefer well-drained soils ranging in pH from neutral to alkaline. If your soil tends to be acidic, you may need to add lime for lilacs to thrive. Always determine pH with a soil test before attempting to adjust it. Check with your state’s Cooperative Extension service for soil testing options in your area.
Lilacs need sunlight, so place them in an area that’s sunny for at least six hours a day. Lilacs rarely flower in shade.
Lilacs generally thrive in USDA Hardiness Zones 3 through 7. In warmer climates, most lilacs won’t get enough winter chill to set flower buds. If you live in USDA Hardiness Zones 8 or warmer, ask a local garden center if they have lilac varieties specifically bred for your area.
If you aren’t sure what your hardiness zone is, find it on the USDA Hardiness Zone Map.
How To Care for Lilacs
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Once established, most lilacs require little attention to provide a memorable annual spring show of scented blooms.
Plant your lilacs as soon as you’ve purchased them. If you buy a lilac in early spring as a dormant bare-root plant, they’re typically sold in a plastic bag with no soil around the roots. Soak the roots in a bucket of clean water before planting.
For all lilacs, dig a wide hole and add compost or other nutrient-rich soil around the roots. Don’t plant the lilac deeper than it was growing in its nursery container. After planting, water well, then cover the ground around the lilac with three or four inches of bark mulch to keep the root zone from drying out too quickly.
If you plant your lilac in the spring, keep it well watered through the growing season. In periods when there is no or little rain, water the lilac deeply once a week during that first season until fall, when the leaves drop and the nights are cooler. Then you can stop watering.
If you plant your lilac in late fall, keep it well-watered until the ground freezes.
After its first year, most lilacs will survive any normally dry periods of the summer with no additional watering.
Pruning and deadheading lilacs
Deadheading — removing spent flowers after they’ve bloomed — helps the plant look tidier, but isn’t required to ensure blooms the next year.
Pruning helps if you’d like to rejuvenate an older lilac. You can do this without sacrificing blooms by cutting out one-third of the oldest branches after blooming. This is especially helpful with old-fashioned or common lilacs (Syringa vulgaris) which can grow up to 12 feet and begin to look like a small tree. Cutting out older branches helps reduce the lilac’s size and encourages new growth.
Remember that lilac flower buds form in the summertime. So if you decide to do any pruning to shape your lilac or contain its size, do so within a few weeks after flowering. Otherwise, you may be cutting off next year’s flowers.
In most home gardens, lilacs won’t need additional fertilizer, especially if they’re grown near a regularly fertilized lawn. If you choose to fertilize your lilac, choose a fertilizer low in nitrogen. Apply it in early spring before the leaves come out, or right after flowering.
Managing lilac pests and diseases
Most lilacs are pest- and disease-free. Some lilacs, especially older varieties, may get powdery mildew on the leaves. This white fungus is rarely treated and doesn’t kill the bush. If you notice any other problems with your lilacs, contact your local Cooperative Extension office to ask for assistance with a diagnosis.
Can You Propagate Lilacs?
Lilacs are generally propagated by taking cuttings of the branches in the spring before they harden into woody stems. These are called softwood cuttings. It’s not the easiest process, but if you have the time and patience, it does work.