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Cutting back a lilac tree

Mike176Mike176 Posts: 21
Hello all,
There is a wildly overgrown lilac at the back of the garden. The flowers are too high up now and there are multiple stems and branches around the base. I will obviously cut back any dead or diseased branches, but just how much would you recommend pruning back overall? Worried I might kill the tree if I really cut back hard.


  • Blue OnionBlue Onion Posts: 2,995
    I've seen neighbors cut them right back down to the ground, pull up the main stumps, and soon it's shooting up all over the area in their lawn.  So I wouldn't worry about a hard prune.. except it looks very shady there.. about how much sun are they getting each day?  They look like they are reaching for the sky.  If they are in full shade, they will suffer from a hard prune and will likely grow leggy and tall again.  
    Utah, USA.
  • Pete.8Pete.8 Posts: 11,287
    I gave my Korean lilac a reasonably hard prune just after flowering and it died.
    It did eventually send a single new shoot out from underground a couple of years later and is a good shrub again, but the hard prune killed everything above ground for several years.
    Best wait until winter

    Billericay - Essex

    Knowledge is knowing that a tomato is a fruit.
    Wisdom is not putting it in a fruit salad.
  • BenCottoBenCotto Posts: 4,679
    edited June 2020
    I gave my lilac a hard prune in early spring I think and it responded by sending out a mass of suckers. The circular bed it was in - approximately 3 metres diameter - was smothered in emerging shoots. I ended up taking the whole thing out and don’t regret it.

    Here are three photos of the lilac: February 2017, May 2017 and last summer

    The lilac is to the right of the shed, right of the plank on the ground

    Suckers are just about visible

    Replaced by geranium Rozanne and Ann Folkard. The herringbone brick path is to the left.

    Rutland, England
  • RhodoNRhodoN Posts: 13
    Hi Mike176, I would choose a main trunk, eventually with a few nice side branches and prune all the rest down to the ground. I would also remove all the growth on the main trunk so that your Syringa will look better. I see that it has flowered this year, so I'd recommend removing the faded flower buds as well. The tree will react by sending up some shoots but you'll just have to prune them back yearly. If you'd like to have flowers at a lower level next year, you could also choose to bend/tie some of the branches and so force the tree into a new shape (just like with roses). I've done it in my garden and it works perfectly. Good luck! :) 
  • Mike176Mike176 Posts: 21
    Thank you all for taking the time out to respond to me 👍
    @Blue Onion - a very shady part of the garden indeed - gets a little summer sun in the morning but mostly in shade - situated in the back-left hand corner of a NW facing garden.
    @Pete.8 - a hard prune it shall not be then!
    @BenCotto - I have to say the Rozanne and Ann Folkard look fantastic. Will they tolerate much shade?
    @RhodoN - Will take that onboard. The tree is actually veering heavily to one side and so I need to get the proper structure back again. Had it in my mind to do a 30% prune all over (i.e. play it safe) but that probably wouldn’t be very effective. Looks like I better invest in a proper saw as well.

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