About The River

Tuesday, June 13, 2017

Proper Pruning for Woody Ornamentals .... Lilacs

Proper Pruning for Lilacs

During my Master Garden Class I learned the proper technique to prune lilacs. I had no idea that the largest stem or large branch of the lilac really should be cut out. I was thinking you would want the old branch.  Pruning helps open the plant up and encourages the new shoots to grow and have new lilac blooms.
And another thing I learned, spring blooming woody ornamentals produce next years flower buds shortly after they bloom. If you want the maximum number of flowers, prune in the growing season shortly after blooming ends.

Below I have included the UW Extension Master Gardener tips to pruning  woody ornamentals. 
Old fashioned, or common purple lilacs are one of my favorite plants. But they can get large (and ugly) if left unpruned for a number of years. The good news is you can easily restore them with proper pruning. Multistemmed spring and early summer blooming shrubs such as lilac, forsythia, bridalwreath sprirea, dogwood, and mockorange should be pruned by cutting off the largest stems at the ground line. I like to prune all of these in the spring before they leaf out so I can get in there and see the stem and branching structure and I don’t have to see around all the leaves. But, spring bloomers, do produce their flowers buds for the next year shortly after they bloom. If you’re going to prune spring bloomers in the late dormant season remember you will remove some flower buds, reducing the number of flower buds in the spring. If you want the maximum number of flowers, prune in the growing season shortly after blooming ends.
Regardless of when you prune, follow the guideline of removing 1/3 of the largest stems at the ground level. Pruning opens the plant up reducing insect and disease problems and encourages new shoots to grow from the root system.   Continue to remove ¼ to 1/3 of the biggest stems each year and in 3 to 4 years you’ll have a brand new lilac with much better shape and size.
There’s another option for old multistemmed lilacs and spring blooming shrubs. The plants can be cut down to the ground before they begin to leaf out in the spring. They definitely won’t bloom that year but will send up many new stems. In a year or two they will grow back into a shrub that will add, not detract, from your landscape.


  1. Thanks, Carla. My Lady Kim lilac bush got damaged in Hurricane Arthur and it looked terrible and last year after it bloomed, I cut off 1/3 of the large branches. I reduced it's hight by about a third all over. Lady Kim always blooms after the regular lilac and I'm waiting to see if it will look better.
    Smiles & hugs

  2. Thanks Carla! We have a big lilac bush by our door, and didn't have a clue how to do this. I have copied and saved this. I also didn't know the new buds form so soon!

  3. Thanks for the helpful info.

  4. This was so great to read today Carla. I have a lilac bush at the new house that is looking so sad and I want to help it. It is right outside my kitchen and I would love to smell those pretty lilacs in the spring. So I am going to do the pruning you suggested and see if this might help it. Thank you for the sweet advice.

  5. Thank you for sharing this! Some of it I knew, and some of it is new to me. Do you remember my lilacs right outside the house? They have been on the 3-4 year plan, but some years I forget, so we are calling it the 8-10 year clean up plan. They are looking so much better than they did 6 years ago though, so I am happy!

  6. Thanks for the tips...and the reminder! I need to get out there and trim the Lilacs, since they've been past bloom for a couple of weeks now. It really does make a difference in the shrubs' appearance the following year.


High Fives from Wisconsin!