Backyard Gardening

By Gerri Miller

Oh, the sweet, sweet smell of lilacs in the spring! The strong fragrance of lilac  flowers brings nostalgic memories for so many. For me, it takes me back to my great- grandmother’s house, where she had lilacs in her flower gardens. I think she gave every one of my relatives a vase full of lilacs in the springtime. It is no surprise that the
National Garden Bureau named 2022 the Year of the Lilac.

Originally from Eastern Europe and Asia, lilacs were first brought to America in the seventeenth century. The lilac (Syringa spp.) is the state flower of New Hampshire, and is a member of the olive (Oleaceae) family. Although there are 20 to 30 different species, common lilac (S. vulgaris) is the most familiar lilac in the United States. Lilac
shrubs and flowers are very attractive. They can be used as border plants, corner plantings, windscreens, or flowering hedges (See Photo 1). According to Michigan State University Extension, “there are over 2,000 cultivars (cultivated varieties) and hybrids of common lilac (https://www.canr.msu.edu/news/lilac_an_old_fashioned_favorite_shrub).” Lilacs come in many colors, such as violet, blue, purple, true lilac, magenta pink, and white. Purple lilac is thought to represent love and spirituality. White lilac is said to symbolize purity and innocence. Purple-colored varieties traditionally have the strongest scent.

The lilac is a very hardy, woody shrub that can live for more than 100 years. Known as the “Queen of Shrubs,” it grows in all parts of the United States except for the south. It needs cold weather to develop flower buds for blooming in the spring, so the mild winters of the south are unsuitable. It is best to plant lilacs in the fall, before the ground freezes. Plant in full sun (six or more hours of sunlight) for the best flowering.

Plant away from walls or fences. Lilacs need lots of space and prefer neutral to slightly alkaline, well-drained soil. It is very important to follow planting instructions for spacing to ensure good air circulation. This will help to minimize such diseases as powdery mildew.

Lilacs need minimal care – another benefit of this beauty! According to University of Minnesota Extension, you may lightly apply an all-purpose shrub fertilizer every couple of years once the lilac has first bloomed. The high nitrogen content of lawn fertilizer may decrease flower production, so avoid applying it on or near lilacs (https://extension.umd.edu/resource/lilacs-identify-and-manage-problems).

The only other care needed is pruning and supplemental watering during times of drought. Although pruning is very important, it is not necessary during the first couple of years after planting, while the roots are becoming established. Wait to prune until after the first time the plant blooms.

You can remove the three D’s – Dead, Damaged, and Diseased branches -at almost any time. It is better, however, to cut when the weather is dry, to prevent the spread of disease. To ensure vigorous growth this year and blooming next year, remove dead flowers right after they wither. Do NOT cut off spent flowers in the summer, fall, or winter, because you might also be removing next year’s flower buds.

Always cut the branches on a slant, not on the horizontal, which may allow standing rainwater to collect and cause moisture-related diseases or the growth of water sprouts. It may be necessary to do some corrective pruning while the lilac shrub is dormant.

Corrective pruning might include:
• Opening up the center of the plant to allow for good air circulation. Do this by removing up to a third of the oldest and thickest stems, as close to the ground as possible.

•Removing crossing or rubbing branches.

•Removing drooping branches.

• Removing pencil-thin sucker shoots and twiggy branches that are crowding the bottom of the plant. The sucker shoots can be used to start new plants, if you also dig out the attached roots.

• Removing or cutting back any branches to shape the boundary of the plant.

After several years of blooming profusely, a lilac bush may become tall and leggy, with the flower spikes growing so high that they are out of reach for cutting. There are several options for bringing down the height of the flowers. One is to cut the entire bush to within a foot of the ground. A drawback to this method is that it may take several years for the lilac bush to bloom again after cutting it completely back.

Alternative methods for pruning tall lilac bushes would involve removing only a fraction of the branches every year, until you have cut back all of the tall growth close to the ground. You could cut back a third of the branches every year for three years, or cut back half of the branches every year for two years. Either way, you will have some blooms every year, while still addressing the height issue.

For more information on pruning lilacs, the University of Maine offers a short video at https://video.maine.edu/media/How+to+Prune+a+Lilac+Bush/1_1w8x1rwv. Lilacs are beautiful, fragrant, hardy, and long-lived. With minimal care, lilacs can bring joy and memories for generations. Just remember that good spacing and air circulation will help prevent diseases. Do lilacs bring back any special memories from
your childhood? Are you ready to smell the lilacs?

Gerri Miller became a Penn State Extension Master Gardener Apprentice in March
2022. She can be reached at clintonmg@psu.edu or through the Clinton County Master
Gardener Hotline at (570) 858-0198