How to Grow Lilacs

One sure sign that spring is here to stay is when the lilacs burst into gorgeous, fragrant bloom. And while many people are only familiar with common lilac (also called French lilac) shrubs that can grow to 15 feet or more, there are many more choices now than there were 50 years ago. Some re-blooming types even add beauty to the garden throughout the entire growing season.

Let us teach you how to select, plant, and grow your own lilacs.

When you go plant shopping, you’re most likely to run into the common lilac. There are many varieties and cultivars of this old stand-by, each producing fragrant spring flowers in shades of white, purple, pink, or even pairings of those colors. Common lilacs can get rangy and big, but are usually the most fragrant type of lilac.

New introductions of hybrids between the common lilac and other shrub-type lilacs have brought rebloomers to the garden center. Some of these newer varieties are a bit less fragrant, but they’re smaller, bloom more than once during the growing season, and tend to have fewer problems with powdery mildew.

One other popular type of lilac is the tree lilac. It blooms with cream-colored flowers in midsummer and can grow to a height of about 20 feet. The tree lilac doesn’t require much pruning, but remember that it is a tree, not a shrub.

All types of lilacs are deciduous, meaning they lose their leaves in the fall.

The ideal spot to plant lilacs is in an area with full sun (at least 6 to 8 hours per day)—give them too much shade and they may not bloom. Lilacs also like slightly alkaline, moist, well-drained soil.

The best time to plant lilacs is in late fall before the ground freezes. The next best time to plant is in early spring after the ground thaws. Realistically, you’re probably going to have to plant lilacs when you can find them at the garden center, and that’s fine—they may just need more watering if you end up planting them during a warmer time of year.

Lilacs grow best in slightly alkaline (6.5 to 7.0 pH), moist, well-drained soil high in organic matter, so do a soil test before planting. If the pH is below 5.5, you’ll need to add lime to increase it. Once you’ve achieved the right pH, it’s time to prepare the soil. To get lilacs off to a nutrient-filled start, improve individual planting holes by blending Miracle-Gro® Garden Soil for Trees & Shrubs with the native soil in a 50:50 ratio. This garden soil also contains phosphorus and iron to encourage root growth and help prevent leaves from yellowing.

1.    Dig a hole twice as wide and just as deep as the plant’s root ball.

2.    Drop a Miracle-Gro® Quick Start® Planting Tablet into the hole to get plants off to a strong start.

3.    Remove the plant from its container and set it in the hole. You want to make sure that the top of the root ball is about an inch above the soil level.

4.    Fill in around the root ball with the soil mixture, pressing on it to pack it firmly.

5.    Water deeply.

6.    To help keep soil moist and stop weeds from growing by blocking their access to sunlight, mulch the area you’ve just planted to a depth of 2 inches, taking care not to pile mulch up against the base of the plant.

After planting, check plants often and water whenever the top inch of soil becomes dry, usually once or twice per week. Count to 10 while you water to make sure you’re giving each lilac plant enough moisture. (Leaves will begin to droop if the plant is getting too dry.) Once plants have been in the ground for a couple of months, you can cut back to watering every other week. During the second growing season and beyond, lilacs won’t need extra water unless your area hasn’t seen rain for a month or more.

After they’ve bloomed in the spring, feed lilacs with Miracle-Gro® Shake ‘n Feed® Flowering Trees & Shrubs Plant Food (following label directions) to help grow strong roots. This plant food is chock-full of ingredients—like kelp, earthworm castings, feather meal, and bone meal—that feed the microbes in the soil, which in turn break down organic matter into nutrients for your plants.

The biggest issue with lilacs—especially common lilacs—is powdery mildew. The best way to avoid this? Buy and plant powdery mildew-resistant lilac varieties (check the plant tag or online description). It also helps to plant lilacs where there’s plenty of air circulation. Don’t bother spraying to control this fungal disease, as it will eventually go away on its own.

Once young lilacs begin to flower (be patient—this may take a few years!), take time to deadhead by cutting off faded flowers off at the base right after they begin to wilt and fade. This will encourage the plant to put more energy into forming new flower buds for the following spring.

Newer, smaller varieties of lilacs need less pruning than the large common lilacs, but all lilacs will grow better and produce more flowers with occasional pruning. Here are some options:

• If you have an older lilac shrub that isn’t blooming even though it’s getting plenty of sun, cut it down to 8 inches above the ground in late winter (March or April), then let it grow out. The following March, select the best-looking 8 to 10 stems and cut them back by half. Cut the rest to the ground. You should see new blooms the following year.
• To rejuvenate shrubs that aren’t blooming well without cutting the entire shrub to the ground, selectively remove 1/3 of the branches all the way back to the ground each year.
• Prune for size by cutting back branches immediately after the shrub finishes flowering.

• Choose lilacs that will grow well in the space you have available.
• Prepare the soil by adding Miracle-Gro® Garden Soil for Trees & Shrubs.
• Plant lilacs in full sun in moist, well-drained soil.
• Feed lilacs in spring with Miracle-Gro® Shake ‘n Feed® Flowering Trees & Shrubs Plant Food.
• Deadhead spent flowers to encourage shrubs to set more blooms for the following season.
• Prune to encourage blooming.