Lilacs

The aroma of lilacs is intoxicating, and fleeting.

Lilacs may only bloom for a couple of weeks, usually near the end of May, but they are worth the wait. These cousins to olive trees and privet shrubs add beauty in a landscape, and the heady blooms are bound to attract pollinators.

Purple lilac bush (Titus Tscharntke) Public Domain

Lilac varieties

The purple standard lilac (Syringa vulgaris) actually comes in 12 varieties. These small trees can range anywhere from 6 to over 32 feet in height! Most lilacs only bloom once a year, though some varieties have double-flowers. There are also some new reblooming, or remontant, varieties that flower multiple times within a single season. If you don’t have room for a full-sized lilac, you can try a dwarf. Dwarf varieties are becoming more popular in landscapes and as indoor plants, reaching heights of only 4 to 5 feet. Dwarf (or miniature) varieties of lilac are mostly variations on the Meyer lilac (S. meyeri), also known as a Korean lilac.

​How to plant lilacs

Autumn is the perfect time to get your lilacs started. If you received an offshoot or root cutting from a friend, don’t worry if it is looking pretty pathetic right now. That’s normal. Simply select a good location and get started. Lilacs prefer well-drained, neutral soil (with a pH at or near 7.0) with lots of organic material. Lilacs hate wet feet, so good drainage is critical, especially in clay soil.

If you want to put lilacs in the ground, you will need to prepare the soil first. This means digging it up (but not when it’s wet) and incorporating aged compost or some other organic material (kitchen scraps, grass clippings, that sort of thing). If all that organic material is fresh, it will take time to break down. If you do not have the time to wait, simply dig the “waste burial holes” around where you want your lilacs. The earthworms and soil microbes will take care of it for you, and the lilac roots will find it. The hole should be as deep as the root ball and twice as wide. Multiple lilac bushes should be spaced 5 to 15 feet apart. Lilacs normally prefer full sun, at least 6 hours, but scorching summer heat really takes a toll on lilacs. They end up needing a little protective shade from nearby trees and shrubs.

White, double-flowered lilac (Arpingstone)

Growing lilacs in containers

To successfully grow lilacs in containers, you will need to select a dwarf variety and a large container. Lilacs prefer having room to spread their roots, so the container needs to be at least 12 inches deep and 24 inches wide. Be sure to use potting soil with a neutral pH. Lilacs dislike both alkaline and acidic soil. Water thoroughly at planting time and keep the soil evenly moist (not soggy) until the roots have taken hold. After that, water any time the top inch of soil dries out, and not before. Containerized lilacs need at least 6 hours of full sun every day to bloom properly. Many homes do not have that much direct sunlight, so you may need to supplement with grow lights. Stabilize temperatures and reduce moisture loss adding a thin layer of mulch, such as attractive redwood chips, around your potted lilac, just be sure to leave a little space between the mulch and shrub stems.

Caring for lilacs

Lilac flowers bloom on old wood, so pruning should be kept to a minimum. Pruning should be limited to removing dead, diseased, rubbing branches, suckers, and spent flowers. Since flowers are produced on older wood, do not put off deadheading your lilacs. If you wait until the end of the season, the wood that grows in will be too young to produce flowers the next season. If your lilac becomes unruly, cut all canes back to eye level and remove one-third of the oldest canes at ground level. The next year, cut half of the remaining old wood down to the ground. In year three, cut the remaining old wood. Or, you can cut the whole thing back to a height of 6 to 8 inches. This more drastic method creates the best blooms, in the long run, but it will take your lilac a few years to get back to full size.

Each spring, top dress the soil around lilacs with aged compost. Then, cover that top dressing with mulch. This will add nutrients and protect the microorganisms that help your lilacs get to those nutrients. Commercial fertilizer is not recommended for lilacs planted in the ground. Excessive nutrients causes plants to produce more leaves, and no flowers.

Lilac pests and diseases

I have found Fuller rose beetles to cause the most damage to my lilacs. Scalloped leaves are a sure sign of this pest. Lilacs are also susceptible to powdery mildew, phytophthora, and pseudomonas. Slugs and snails are said to cause some damage, but I have not had that experience.

Propagating lilac

If you already have a lilac, you can take root, shoot, and sucker cuttings to propagate new plants. Dig up some roots, or suckers with roots attached, and place them in a bucket with some water until you are ready to plant. You can also use 8 to 12 inches new growth twigs. Simply strip away most of the lower leaves and place them in rich potting soil and keep them moist (above and below ground) until roots start to grow. Since woody stems can be difficult to start rooting, many people apply rooting powder to the lower portion of the stem. Since rooting powders are synthetic plant hormones, I don’t use them.

While lilacs are not edible, I can practically taste their sweet fragrance. Also, the pollinators who are drawn to lilac blossoms often stick around to pollinate other plants in your garden.