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leylandii trunk growth

In our garden we have inherited a cluster of 3 Leylandii with a good 1m+space within where we plan to build a small (low level) tree house for our toddler.  The tree house will be supported fully by posts and fill the space created by the tree triangle.  My question is how much space do you think we should leave for trunk growth?  I don't know the age of the trees but they are atleast 15 feet tall with a trunk diameter of approx a foot each (maybe more).

What would you advise?

Many thanks


  • fidgetbonesfidgetbones Posts: 17,237

    I'd take the tops out at about 10 ft. They will grow at 2 to 3ft a year and before long you wont be able to get to them and they will be out of control. Assuming you are going to trim out the inner branches of the triangle, allow up to 6 inch for growth room from the trunk. When you prune back into brown wood it will not resprout.

  • Thank you for the advice image We currently trim them down yearly as we like their height-lots of overloooking windows!  We are also lucky to have excellent access from all sides. Will tarp the centre in future prior to cutting to protect treehouse from stray bits and the centre is ready to start with a nice big hollow space.

    How long do you think it would take for the trunks to grow by 6 inches in diameter?

    Thanks again

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