This is a first in a regular series of articles on the care and maintenance of some of our favorite plants for northern gardens.
With their lush blooms and deeply floral fragrance, lilacs are a harbinger of summer in the northern garden. They generally bloom from early to late May at the same time as other flowering trees and shrubs, such as apple, crabapple and cherry trees.
Lilacs are easy to grow and can serve a variety of purposes in the garden. The large common lilacs (Syringa vulgaris) form dense hedges that birds love to hide their nests in. New varieties, such as the more petite ‘Miss Kim’ lilac work well as specimen plants or dainty dividers in urban yards.
How to Grow Lilacs
For the best flowers, plant lilacs in full sun (6 to 8 hours a day) and in well-drained soil. Lilacs perform really well in Minnesota’s slightly alkaline soils. They need ample water, especially when first planted, so if Mother Nature does not provide it, you should supply about an inch of water per week. (No need to worry in our very damp spring of 2013!) Lilacs should be given adequate space—usually 5 or more feet between plants—to grow to their full size.
They do not need an excessive amount of fertilizer. A layer of compost in spring or a light sprinkling of a 10-10-10 fertilizer should do the trick.
The most important part of lilac care is pruning. You want to deadhead as many of the spent blooms as you can. Go ahead and cut a big bouquet to bring in the house or give to neighbors—your plant will thank you with more blooms next year. Buds are set on old wood, so the best time to prune is right after lilacs bloom in early summer.
In addition to deadheading, you will want to remove branches that are dead, distorted or diseased. Lilacs benefit from fairly serious pruning, but never remove more than one-third of the bush. Renewal pruning—when you remove one-third of the branches down to the ground—may be necessary on older lilacs.
—Mary Lahr Schier