Master Gardener Ciscoe Morris is back with us, and this time he's talking all about lilacs! He shares with Amity how to keep these beautiful flowers in great condition so they'll last longer and bloom again the next year.
Lilac trees are among the most popular of all small trees grown in the Puget Sound region. No other plant offers a scent that can match that of lilac, but if you don't get the right variety and care for it properly, growing a lilac can be a frustrating experience.
In the first place, not all lilacs are fragrant. There are hundreds of varieties and they all have different scents. If you're after great fragrance, buy your lilac when it is in bloom at the nursery. That way you can do the sniff test and find one with the perfect fragrance and pick your favorite color as well. A few good ones to check out include 'Lavender Lady', a profuse bloomer with big lavender flowers that emit a strong, pleasing aroma. The pink blossoms of 'Maiden's Blush' are renowned for extremely intense lilac fragrance with cinnamon overtones, and the large, very fragrant wine red blooms of 'Congo'' open red and mature to purple.
As spectacular as they are caring for lilacs can be somewhat frustrating. That’s because they often take a long time to begin blooming after planting, and by the time they finally begin producing before you know it, they've grown to 20 feet tall with most of the blooms occurring out of reach in the top third of the shrub. When you buy a new lilac, the only pruning needed is to cut back overly long stems to nodes farther back on the branch to promote bushy growth. Once flowering begins, however, annual pruning is needed to control for height and promote heavier blooming.
Every spring, soon after the flowers fade, remove the spent blossoms by cutting back to a pair of leaves or a side branch slightly farther down on the stem. Removing the spent flowers before they are able to set seed will prevent the tree from wasting energy ripening seed, and will encourage increased flowering next season. At the same time, pruning every spring after the blooms fade will help keep the tree from growing too tall. If your lilac is already taller than desired, right after the blooms fade cut back a few of the tallest stems to vigorous side branches 2/3rds of the way down the branch. Remember, however, that on most lilacs blossoms are produced on the previous season’s growth, so don't cut too many branches down hard or you'll pay for the reduction in size with reduced flowering the following spring.
If you don’t have room for a 20-foot tree, consider planting one of the dwarf Korean lilacs (Syringia meyeri). These small, sturdy shrubs rarely sucker, can be kept below six feet, and are equally at home growing in a pot as out in the garden. The trees may be smaller, but the flowers are every bit as fragrant. ‘Palibin’ with powerfully fragrant, pinkish lavender blossoms is the smallest of all lilacs maxing out at about four feet. ‘Superba’ gets only a smidgen taller, and its sweetly scented, deep pink flowers are among the longest-lasting of lilacs. The newly introduced Syringa x ‘Bailbelle’ Tinkerbelle rarely exceeds six feet and is an olfactory delight. The deep pink single flowers emit a rich, spicy fragrance guaranteed to please. Although it isn't a Korean species, Bloomerang® Purple Syringa x 'Penda' is a European hybrid that stays under six feet tall and is famous for reblooming later in summer with pinkish purple fragrant flowers. All lilacs perform best in full sun, and well-drained soil. Lilacs prefer alkaline soil, so apply lime every few years to prevent the soil from becoming too acidic.
Finally, if your tall growing lilac drives you crazy by producing gazillions of suckers around the base of the plant, other than cutting the suckers down every spring, there are only two other ways to prevent the problem. Either you can dig and remove your lilac, or you can sell your house and move, because nothing will stop the suckers from coming up in ever-increasing numbers each year. If neither of those methods are possible, buy a good pair of loppers and a file to keep them sharp. You're going to be doing a lot of pruning. The average lilac lives for well over a hundred years!