Lilacs are magnificent and fragrant flowering bushes or trees. In this guide, we’ll cover basic lilac care, from planting to pruning, so you can help your plants produce healthy and colorful blooms year after year.
Choosing the Right Lilac Variety for Your Growing Zone
Most popular varieties can thrive in USDA zones 3-8, i.e. throughout most of the United States.
For those living in areas with harsh winters, the exceptionally cold-hardy common white lilac (Syringa vulgaris var. alba), which can tolerate USDA zone 2 temperatures, is a good fit.
Anyone in hot climates with mild winters (USDA zone 8 or above) can still enjoy the visual effect of lilac flowers with shrub species that have features so similar to the traditional (Syringa) lilac, they even have the word “lilac” in their common names:
Where to Plant Lilacs
Lilac Soil Requirements
Lilacs prefer well-drained soil with a neutral or slightly alkaline pH level (around 6.5 or 7.0). The soil should be rich in organic material. Before planting, improve the growing medium by adding garden soil or humus-rich compost.
If you’re gardening in an area with heavy clay soil, it’s best to find a spot with a slight slope. This will allow water to drain away from the roots and prevent the soil from staying too wet.
Do Lilacs Need Full Sun?
Lilacs love sun! More than six hours of full sun per day is ideal.
If you live in an area that experiences intense summer heat, then some shade may be beneficial during midday. However, in most areas, the more sun exposure the better.
Lilac Space Requirements
Most lilac bushes should be planted at least five feet (1.5 m) away from each other to ensure they have enough space for optimal growth. However, some varieties can grow quite large, and therefore require more space for expansion, up to fifteen feet (4.5 m) apart.
Follow the recommended planting guidelines for the variety you’ve chosen so that your shrubs have ample room to grow and thrive.
When to Plant Lilacs
Plant lilacs in the spring after the ground has thawed and as early in the season as possible.
In regions with mild winters, fall planting (between mid-August and mid-October) is also an option. Early fall planting allows for a period of root growth before the ground freezes, resulting in a stronger support system for future growth in the plant’s above-ground parts.
How to Plant Lilacs
Choose a suitable location—see sun, soil, and space requirements above.
- To prepare the site, dig a hole twice as wide as the root ball and deep enough to accommodate the root system. The depth of the hole should be such that the top of the root ball is level with the ground.
- To prepare the soil: mix organic matter such as compost or peat moss with the soil that was dug out to make the planting hole.
- Place the young shrub in the hole, backfill the hole with the amended soil, and gently press the soil down to remove air pockets.
- Water the newly planted lilac well. Make sure that the soil is moist down to the root level.
- After planting your bush, mulch it with a layer of organic material, such as shredded leaves, straw, or bark. Mulching helps to retain soil moisture and prevent weed growth.
How to Grow New Lilac Plants from Cuttings
It’s possible to grow a new lilac plant from a cutting, but you shouldn’t expect this method to work every time. Success depends on taking your cutting during the right time of year, which is a small window of time when your existing lilac bush is producing new growth.
Follow these steps to grow a new lilac plant from a cutting.
- In late spring or early summer, take cuttings from lilac bushes that are producing tender new growth. The stems should be fresh and green, not mature and hard. Cuttings should be 4-6 inches (10-15 cm) long and should not have flowers.
- Strip the bottom leaves from the cuttings, leaving two to three leaves at the top.
- Fill a pot with a mixture of potting soil, sand, and perlite.
- Moisten the mixture lightly and use a stick or your finger to make a planting hole.
- Dip the bottom of the cutting in a rooting hormone (a chemical product that stimulates root growth), then plant it in the hole.
- Pat the potting mix lightly around the base of the cutting so that it stands up straight. You can plant several cuttings in the same pot, as long as they’re not touching.
- Place your newly potted plant under indirect light indoors until it develops roots. This could take anywhere from two weeks to two months.
- Water the cuttings daily, or as often as needed to keep the potting mix slightly moist but never soggy.
- Once the plant has developed a strong root system, you can transplant it into the ground.
Lilac Care and Maintenance
To ensure that your shrubs stay healthy and vibrant, regular pruning is essential.
Pruning promotes flowering, removes dead material and unwanted sucker growth, and keeps the bush looking tidy and attractive.
When to Prune a Lilac Bush
Major pruning isn’t necessary for the first few years of growth. For mature lilacs, prune in early spring (before new blooms appear) or shortly after the season’s blooms have faded.
How to Prune a Lilac Bush
- Prune with sharp shears that can make clean cuts.
- Cut off excessive growth to reduce the shrub to a manageable and attractive size. Remove sprawling growth to create a bushier and more compact shape. After a few years of pruning, you’ll have a lilac that’s completely covered in blooms.
- If your plant has already grown much larger than you’d like it to be, remove some main stems at ground level. However, to protect the plant’s health, don’t remove more than one third of its total growth in any given year.
Deadheading is the process of removing spent blooms. While this will not extend the current bloom season, it may encourage new growth and more abundant flowering next season.
To deadhead, simply snip off dead flowers. Cut just below the start of the flower cluster, leaving the stem and leaves in place.
Fertilizing Your Lilacs
While lilacs do not require frequent fertilization, an occasional treatment is a great way to promote healthy growth and blooms.
The best time of year to apply fertilizer is in early spring. This ensures that the plant has access to all of the nutrients it needs during its active growing season.
If your area has clay soil or other soil types that could impede nutrient uptake, consider using a slow-release fertilizer two or three times throughout the summer. When choosing a fertilizer for your lilac bush, look for one with a nitrogen, phosphorous, and potassium (NPK) ratio of 10-10-10. You can also add organic options such as compost, manure, or bone meal for additional soil amendment.
Lilac Care: Troubleshooting
Help, My Lilac Isn’t Blooming!
If your bush isn’t blooming, a lack of sunlight might be the problem. At least six hours of direct sun per day is best for generating blooms. Additionally, provide water around once per week during dry weather in the blooming season.
Keep in mind that lilacs produce blooms on growth that started last year. It’s a patient process: this year’s care helps to generate next year’s blooms.
Signs That Your Lilac Needs Fertilizing
If you see yellowing leaves or other signs of poor health in your lilac bushes, it could be an indication that they are not receiving enough nutrients from their soil.
Signs of poor nutrition in lilacs include leaf dropping, discolored foliage, wilted stems and branches, and reduced flower production.
Lilac Pests and Diseases
Insects that can damage lilac plants include Japanese beetles, aphids, mealybugs, borers, and scale insects. To limit vulnerability to these pests, keep your plants properly watered and fertilized throughout the growing season.
Signs of an infestation include holes or discoloration in the foliage. If you suspect the presence of pests, inspect the plant closely. Remove any pests that you find along with damaged portions of the plant. You can also treat the affected area with insecticidal soap or neem oil.
A common fungal disease for lilacs is powdery mildew, which appears as white spots on foliage. Powdery mildew is mostly an aesthetic issue that won’t kill the plant. To prevent the spread of mildew, provide your plants with adequate spacing and treat affected areas with fungicide.
Growing Lilacs in Your Layered Landscape
Common lilacs grow up to 20 feet (6 m) tall, offering a colorful option for the upper level of a layered garden. For more suggestions on developing a garden that’s full of varied heights and textures, check out Layered Landscaping: Garden Planning from Tall to Small.