Rejuvenation Pruning Keeps My Favorite Ornamental Blooming Strong

By Laura Miller | January 13, 2022
Image by Roxana_ro
by Laura Miller
January 13, 2022

Few ornamentals bloom as aromatically as the lilac. I love stepping out my back door and being assaulted by that fresh lilac fragrance. It permeates the air, lingering gently on the breeze to remind me that spring is finally here; and when I want that beautiful lilac fragrance in my home, no problem. Lilacs also make wonderful cut flowers.

Growing Lilacs

As you probably guessed by now, I’m a big fan of Syringa vulgaris, the common lilac. I have several of these large ornamental bushes in my yard, including the one sitting right outside the window near my desk. I often take a break from my writing to enjoy the delicate lavender-colored blossoms waving gently in the breeze.

I’ve found, however, that keeping lilacs blooming year after year can be a challenge. These long-lived shrubs can grow for decades, yet lilacs bloom on last year’s growth from branches that are generally under five or six years old. As my lilac bushes age, they tend to produce fewer blossoms and these flowers are located out-of-reach on higher branches.

Pruning a Lilac

While properly pruning lilacs on an annual basis can help them bloom better, I’ve found my lilacs also benefit from periodic rejuvenation pruning. So how can I tell when a simple pruning is in order or if it’s time for rejuvenation pruning? I start by taking a good hard look at my lilacs and I consider these factors:

  • Flower output – Did my lilac bloom heavily or did it only produce a few blossoms? While an unimpressive lilac bloom can indicate it’s time for rejuvenation, this can also be caused by other things, such as pruning lilacs at the wrong time of year.  
  • Plant shape – As my lilacs age, they tend to develop a less pleasing shape. Instead of being full and round, the trunks push the green growth upward. This gives the lilac bush a tree-like appearance.
  • Dead areas – Branch die-back creates unsightly holes in the canopy of the lilac bush. Pests and disease can be the culprit, but size and maturity of the limbs is often a factor with aging lilac branches.
  • Trunk condition – When I see the above three symptoms, I stick my head inside the lilac bush and examine the trunk. Splits and cracks are a good indication that it’s time for rejuvenation pruning. 

Luckily, lilacs are very tolerant of heavy pruning. I cut back all the main trunks, leaving only a few choice shoots. It’s basically like starting over with a new shrub, but the intact root system doesn’t need to become established. The rejuvenated lilac regrows quickly and before long that magnificent lilac fragrance is again permeating the yard again each spring.

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