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How to cut back or pune a 15ft Lilac tree

kjavwkjavw YorkshirePosts: 14
  I am looking for some informed advice on how and when to cut back a lilac tree?  As you can see from the photo there are no suckers and the tree gives a glorious display every year but its blocking all the light from the kitchen window and is on its way up to the bedroom window and I want to cut it back before it gets there, without killing it off.  We don't mind if it misses blossoming a year.  How severe can I be without harming it?

Not sure if it makes any difference but it is heavy clay soil and the tree thrives every year.  I have cut it back for them a couple of times (its nearly 50 yrs old) to no ill effect but I am an amateur and don't want to harm the tree. Most stuff I find refers to lilac bush and this seems to be a tree to me?


  • ObelixxObelixx Vendée, Western FrancePosts: 28,363
    Generally speaking, lilac should be pruned after flowering finishes and not too drastically.   This keeps them in shape and encourages the production of new flower buds for the following year.  They are classed as shrubs but can become very large if not maintained.

    If you want to do renovation pruning and don't mind missing out on flowers you can do this any time between now and the ned of winter when frost is not forecast.

    Start with clean, sharp tools such as a pruning saw, loppers and secateurs depending on the thickness of branches.  Remove any dead, damaged or diseased looking stems back to their base.  After that, remove any stems that cross with others as these may rub and cause damage to the bark that lets in viruses, pests and diseases.

    Then step back and look at the shape of the shrub.   If it looks balanced, leave it alone.  If it looks lopsided remove stems as far back as you need to balance it but go easy.

    Just cutting the whole thing back to short stems or a stump in one go will provoke the lilac to produce lots of water shoots and a thicket of stems which will be hard to manage and make attractive so be patient and do it over 2 or 3 years.   Once you have strong, fresh new stems growing you can take more of the older ones out.
    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
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