Extensive cultivation and hybridization have created more than 2,000 cultivars of the common lilac (Syringa vulgaris), introduced to this country before 1700. Lilacs are easy to grow, but they require specific growing conditions to reward gardeners with their showy spring flowers and namesake fragrance.
Plant a lilac in well-drained soil that is slightly acidic to neutral in pH. Fertilize in the spring with a balanced fertilizer, following label instructions.
Soil
Lilacs thrive in full sun and well-drained soil that is neutral to slightly alkaline. If you are growing them in containers, fill with a high quality potting mix such as Scotts Osmocote Premium Potting Mix. When transplanting, gently remove the lilac from the container and loosen the roots. Dig a hole that is twice the size of the root ball, then backfill with the potting mix and water well. A light layer of mulch helps retain moisture and keeps weeds down, but be sure it is not touching the base of the plant to prevent insect borers.
If you are planting a lilac from seed, sow the seeds in spring. They are self-pollinating, and grow true to the parent cultivar. Lilacs can also be propagated by cuttings in early summer (not recommended for grafted plants).
Lilacs prefer well-draining soils that are slightly acidic to slightly alkaline and rich in organic matter, but they tolerate a variety of conditions. Do a soil test before planting to ensure your lilac has the right balance of nutrients. For best results, aim for a pH of 6.5 to 7.0.
Once established, lilacs can handle drought conditions. However, they will not bloom if the foliage is constantly wet or if there are frosty spells in the spring.
If your soil is sandy, amend with compost to give the lilacs a more loamy base. If your soil is clay, add gypsum to help loosen the soil. Lilacs benefit from being spaced based on their mature size. Proper spacing will not only keep the shrubs in shape, but also improve air circulation and reduce the potential for powdery mildew.
If you are planting a lilac that was grown in a container, amend the potting mix with 10 percent compost and 50 percent Miracle-Gro(r) Garden Soil for Trees & Shrubs. Then, plant the lilac in a sunny location, digging a hole that is as deep as the potting mix was in the container and just as wide.
Water
Lilacs are tough and adaptable plants that thrive in a range of conditions. They grow well as specimens, in groups or rows, and even as hedges for privacy. They also grow well in containers, but it is important to provide regular watering and fertilization for them. Lilacs prefer full sun but will tolerate some shade. However, in too much shade, they will not bloom as profusely.
Plant your lilac in fertile, humus-rich, loamy, neutral to slightly alkaline soil with sharp drainage. They can also take clay soil, but it might stunt growth. Compost is a good way to amend acidic soil. A soil sample can help you determine the pH of your garden; if it is low, you may need to add liming to raise it.
Young lilacs need frequent watering to establish their roots. But they need less supplemental water after that as long as it is not in soggy conditions. Soggy conditions encourage root rot and can stifle flower production. Lilacs can survive a mild drought but will benefit from watering during hot, dry weather.
Because they are hardy shrubs, lilacs do not require winterization or covering in areas with subzero winter temperatures. But they do best in a site that is protected from harsh winter winds, which can damage the flowers and buds.
Lilacs come in a variety of sizes, including dwarf varieties that only reach 2 to 3 feet high. Larger species, such as Syringa repens ‘Palibin’ and S. x laciniata ‘Miss Kim’, offer fragrance and a gracefully rounded shape that suits the landscape. If you don’t have room for a large lilac, try the compact ‘Baby Kim’ or S. x meyeri ‘Scentara Double Blue,’ which are both a bit shorter.
If you’re unsure which lilac to choose, consult the website of the Plant Breeders’ Association for a list of cultivated cultivars, along with their growing and blooming information. Some of these cultivars are resistant to powdery mildew, leaf spots, borers, thrips and other pests that can infest traditional lilacs. Lilacs are also tolerant of pollution and urban conditions.
Pruning
Lilacs are a beloved flowering shrub that bloom in the spring. The fragrant blooms often have a deep purple color, but the plant also comes in blue, lavender, pink and white varieties. Lilacs are easy to grow in the garden and can thrive for decades. They are not bothered by most pests, but lilacs should be pruned regularly to encourage more blooming. This plant requires well-drained soil to thrive and it will not grow in shade or part sun conditions.
When pruning a lilac, only remove dead, damaged or diseased branches from the plant. Woody plants like lilacs can compartmentalize wounds to limit infection from disease or insects. It is best to remove diseased branches immediately, so the lilac can heal quickly. For the best bloom, a lilac plant should be pruned right after it has finished blooming in the spring. If the plant is pruned later in the season, you will cut off buds for next year’s flowers.
It is a good idea to mulch around the base of a lilac, which will help keep the soil moist and suppress weeds. The mulch will also help keep the roots cool, which helps promote more blooming. Lilacs are fairly resistant to most problems, but they can be susceptible to powdery mildew and borers. Use natural remedies or chemical fungicides to treat these problems as soon as you notice them.
Lilacs are hardy in most parts of the United States and can be planted as an accent or border for a home garden. They are the perfect addition to any landscape because of their beautiful colors and fragrant blossoms. The flowers are an iconic sign that spring has arrived and their fragrance is a welcome relief from the cold winter months. This plant is also a popular choice for commercial landscapes because of its versatility and durability. With proper care, a lilac plant can live for many years and be enjoyed by families for generations to come. Naomi Slade is the author of “Lilacs: Beautiful Varieties for Home and Garden” (Gibbs Smith, April 2022). Her no-fuss gardening tips and exquisite photos show that anyone can grow these enchanting plants.
Blooming
Lilacs grow best when they receive full sun. If they are planted in shade, the flowers may not be fragrant or showy.
Planting a lilac in poor soil, or planting it too deep, can also prevent the shrub from blooming. Lilacs need rich, well-draining soil. If you have clay soil, amend it with compost to improve its texture and drainage. Lilacs thrive in moderate amounts of moisture, but soggy soil can cause root rot or stunt growth.
The first year after planting, a lilac should be watered regularly to establish its roots. After that, it needs only enough rain or irrigation to keep the ground moist. If you live in an area with a very dry climate, mulch the lilac to retain moisture.
If a lilac fails to bloom, it could be due to poor pruning or a disease. Pruning a lilac too soon after flowering removes next season’s buds. If the lilac has been infected with lilac blight, brown spots on the leaves and stems will eventually kill it. Infected branches should be removed promptly.
Lilac plants that are pruned too late in the fall, or even into winter, will also fail to bloom. If the lilac is planted in full sun, it should be pruned just after blooming in spring. If a lilac is planted in partial shade, it should be pruned after the blooms fade in early summer, and then only lightly throughout the growing season.
If you have limited space for a large lilac, there are several smaller varieties that will not outgrow their containers. For example, the ‘Baby Kim’ cultivar has fragrant single flowers in shades of blue and purple, and it grows only 2 to 3 feet tall and wide. Other compact lilacs include the double-flowered ‘Scentara Double Blue’ and the ‘Blue Sky’ variety, both available from Proven Winners.
The Mackinac Island Lilac Garden, located in Lake Huron in Michigan, features more than 100 varieties of common lilac, as well as a few other species. This lilac garden’s cold winters and warm summers provide excellent conditions for the plants to flourish.
