CORVALLIS, Ore. — The lush fragrance of lilacs defines late spring.
These hardy shrubs are as durable as they are beautiful — cold hardy, tolerant of city conditions and not fussy about soil. They make vigorous, tall screens and striking flower displays. Even when bare, younger lilacs have an attractive branching pattern in winter.
Lilacs produce the most flowers on healthy, new growth rather than on older stems, said Ross Penhallegon, retired horticulturist with the Oregon State University Extension Service.
To keep lilacs looking their best, prune, fertilize and shape them almost every year — soon after they finish blooming in late spring. Don’t wait too long, because next year’s buds begin forming in summer. Pruning in winter removes those buds and eliminates the following spring’s blooms.
Renovate old, overgrown lilacs gradually
If a lilac has become thin and overgrown, rejuvenate it by removing the oldest branches over two or three consecutive seasons, always right after flowering.
In the first spring, remove about one-third of the old canes all the way to the ground. The oldest canes have scaly, cracked bark and dry, brittle wood. If the lilac is a grafted variety, be careful not to prune below the graft union.
During the next two years, remove the remaining older stems in stages. The lilac should respond with vigorous new shoots from the base and produce more flowers lower on the plant.
Maintain shape and encourage blooms
Once a lilac is rejuvenated, remove faded flowers each year to stimulate new growth and encourage more blooms the following spring. Fertilize in spring with a general-purpose organic or conventional fertilizer, and thin overhead tree branches to ensure plenty of sunlight — a key factor for healthy lilac blooms.
Previously titled Prune lilacs soon after bloom
