Fall is the wrong time to prune lilacs


For most gardeners, Lilac means the traditional “old-fashioned” shrub that graces so many old farmhouses, and probably your grandmother’s garden. We can all remember the huge bouquets of fragrant purple blooms filling our grandma’s huge glass vase and how they filled the entire house with perfume. The traditional Lilac family “Syringa vulgaris” or common lilac remains the most popular, and hundreds of variations exist today in the nursery trade.

Common lilacs generally grow very large. Bloom colors range from white and creamy yellow to pink, “red” (actually dark pink), lavender, blue and purple. Blooms can be single or double, sometimes with white edges. There are over 400 cultivars. Lilacs are not generally heat tolerant, doing better north of the Ohio River where summers are cooler. Most are susceptible to powdery mildew, which makes the leaves appear dusty or moldy in the late season. This problem is not really harmful to the plant, but if it offends you it can be treated with sprays containing copper fungicide.

Commercial landscapers have discovered the dwarf Lilac family “Syringa meyeri”, otherwise known as Syringa “patula” or sometimes “palibin”. These plants are more compact than traditional lilacs, are not as susceptible to powdery mildew, blights, borers and scale insects. They have a more compact form, generally growing to about 6 feet. The most common varieties are “Miss Kim” and “Dwarf Korean”, which make good foundation plants because of their compact size and naturally tidy shape.

Due to the popularity of the compact Lilacs, new varieties are being introduced regularly. Our favorites include “Tinkerbelle” and “Thumbelina” from Bailey Nurseries, which have an outstanding fragrance and redder bloom color. Both are also available as dwarf trees. Another popular new lilac is the re-bloomer “Bloomerang”, a compact version of the popular “Josee’’ old-fashioned lilac, which blooms twice each year.

Older common Lilacs can become unsightly due to dead wood in the center of the clump, and an irregular shape. Older plants can be rejuvenated by cutting them off six inches above ground after spring bloom, and letting them re-grow all new canes. We call this the “bush hog approach”. It will take a few years before they will bloom again, but this drastic “tough love” approach will create a very full, luxuriant mounding Lilac shrub that is much healthier and stronger.

Dwarf Lilac bushes should be sheared each year to promote compact habit of growth, and to multiply the number of blooms. Lilacs form their flower buds during summer, so if you shear them in fall or winter they will not bloom in spring. Unlike most shrubs, lilacs should only be sheared in late spring after they bloom, before they sprout new growth.

Steve Boehme is a landscape designer/installer specializing in landscape “makeovers”. “Let’s Grow” is published weekly; column archives are on the “Garden Advice” page at www.goodseedfarm.com. For more information is available at www.goodseedfarm.com or call GoodSeed Farm Landscapes at (937) 587-7021.


By Steve Boehme

Contributing Columnist

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