Asked August 20, 2014, 6:25 PM EDT

Can I trim Leland cypress trees the trees are about 20' tall and some of the branches are over an area the needs to be cleared for passage , will the trees die if I trim if I can trim when will be a good time to do

Kent County Delaware

1 Response

The best time to trim Leyland cypress is in the spring (April). You can prune up until the end of August. Here is some information about pruning Leylands. It is primarily referring to maintaining them as a hedge, but also talks about reducing overall size near the end of the passage.

How to prune Leyland cypress

Formative pruning young hedges

  • Year one: trim back the overlong sideshoots at the start of the growing season in April. Trim sides lightly in July and tie in the leader to a supporting cane as it grows. This will encourage dense growth
  • Second year: trim sideshoots again to encourage further dense growth and leave a neat appearance over winter
  • Subsequent years: continue trimming the sideshoots, but not the top of the tree, until the desired height is reached
  • Once the desired height is reached: in the following spring, shorten the leading shoots to 15cm (6in) below the required height. The new growth will make up the difference and form a thick top

Established pruning

  • Trim the top and sides up to three times in the growing season (between April and the end of August)
  • Shape the hedge to an inverted wedge – a flat-topped A-shape. By keeping a wide base, light reaches all parts of the hedge evenly and ensures the base does not become brown and bare

Pruning overgrown hedges

  • With its rapid growth, a Leyland cypress hedge can soon become overgrown if not maintained at the desired height
  • Healthy plants will usually respond well to reduction of up to one-third of the height. This is best carried out in early April as the new growth is about to begin
  • Taking too much off the top can result in a bare, flat-topped hedge. Worse still, it may result in the death of older or less vigorous plants
  • Where essential to reduce height by more than one third, it is possible (although not recommended) to reduce by one third in the first instance and then, when the plants have recovered, reduce the remaining plant by up to one half
  • If reduction in width is required, care needs to be taken not to cut into older leafless growth as new growth will not appear from bare wood