Trimming Syringa or Lilac Bush


The Syringa or better known name Lilac are one of the spring beauties in the garden that will continue to bloom for centuries if pruned regularly.  Proper pruning will mean endless blooms year after year.  When a lilac bush is left unattended it can grow to a height of 15 or 20 feet and will only have blooms on the top branches.  The best time to prune is right after the blooms die off.  This ensures that your pruning will not affect the blooms for the following season.  When taming an overgrown lilac through pruning remember new shoots left to grow will not all have blooms the following year.  Some will take two to three years to bloom.  A healthy lilac will have blooms throughout the shrub rather then just on top.  Never ever prune more then one third of the shrub as it can stress the plant.

The healthiest lilac will have a balance of new and old shoots.  Lilacs continue to throw up new shoots and many suckers every year…just be sure not to prune all of the new ones.  Always start with pruning the dead and woody stalks first.  Follow this by trimming the larger stalks all the way to the ground.    An overgrown shrub will mean that many of the stalks can and will be as big around as a small tree.  The goal is to have most of the branches no larger then 2 to 3 inches.  Remember if it is extremely overgrown and you must prune much of it away…don’t be disheartened if it doesn’t have many blooms the following year.  As long as there is plenty of leaf cover it will recover…sometimes it takes a couple of years.  As with this one I trimmed last summer will.  It had reached a height of 12 to 15 feet and had very few blooms.  It was misshaped and very overgrown.

I pruned both from the bottom and the top to ensure it would have a better shape, be more manageable and would recover with lots of blooms within a couple of years.  I also pruned the inward buds off of the plant and left the outward facing buds to ensure it would fill out better.  Lilac continue to regenerate every year by throwing out new shoots.  Finding the right balance is the answer.  Simple maintenance pruning will only be required now on an annual basis…usually in the spring.  Just cut out the pencil thin or twiggy new growth leaving the best new growth to replace the old.  Then after it blooms, keep its height in check by trimming any leggy growth on top.

Remember, the best time to trim is right after blooming because the lilac sets the next seasons buds almost immediately.  It doesn’t mean you cannot trim at any other time, it just means you will be sacrificing some of the flowers if you trim before or after they bloom.

Use your discretion, sometimes an overgrown lilac will not need to have 1/3 taken out.  It is always better to trim less then more.  Once trimmed you cannot fix but with less trimmed can always do another trim later on.

Remember, next year’s blooms are dependent on this year’s weather.  Some years you will have an abundance of beautiful blooms and other years not so much.  If the plant is stressed due to weather conditions it will show it the following year.  Lilacs are hardy so don’t worry it will recover.

See you in the garden or the garden centre! 🙂

Lilac area 1Lilac area 2Lilac area 3Lilac area complete

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