Overgrown evergreen hedge? Here’s what to do

December 22, 2023

We are frequently asked how to deal with an overgrown evergreen hedge like the exceptionally quick-growing Cypress tree. Often used as a hedging plant, quite often inherited from a previous homeowner, and while good wildlife habitat because they are very dense and offer good cover for bird life, they can become difficult to deal with when they get big and outgrow the space.

Leyland cypress (Cupressus × leylandii) is a sterile hybrid accidentally created in Wales from two species of cypress from North America. Leyland cypress is not found in the wild. It is fast-growing and works well in its natural form, far down at the end of the garden and allowed to grow naturally. However, problems can arise when they are grown as hedges. Thanks to their fast growth, you can create a nice, thick green wall, tall enough to block off a neighbouring view, that you don’t need planning permission for, but you must be meticulous in the maintenance thereafter, or they can cause a horrible problem if allowed to become an overgrown evergreen hedge.

*This Leyland cypress hedge is a prime example of an overgrown evergreen hedge. It has been hit hard with a tractor-mounted flail hedge trimmer. Parts of it are dead and will not recover.*

The problem when using this species as hedging is that if you trim or prune the branches back too much, then the branch dies, and you’re left looking at a brown stick. The reason for this is that there are no dormant buds in the woody part of the branch; the buds are all in the green leaves at the end of the branch. If you trim off all the green bits, it can’t regenerate the branch and grow leaves again, so it dies.

For other hedging plants, you can do a hard prune, but for this one, you can’t. You, therefore, can’t do a hedge reboot if it gets too big. So, you must live with a big green blob that doesn’t allow any light through, trimming it all the time, or you must get rid of it and replant or have a fence or both. Lots of people in Edinburgh have this problem.

This is kind of what Leyland Cypress is supposed to look like however the crab apple to the right is suppressing its growth. The cypress is also suppressing the crab apple growth. Cypress will usually outcompete and dominate other species because they are fast-growing and block out light.

Cupressus x leylandii can get enormous. We’ve removed some with trunks bigger than two metres in diameter. The biggest one recorded is forty metres tall and still growing. Leylandii, as they are usually called around here, have been known to grow to fifteen metres in 15 years! That’s a lot for a tree. If you think about grasses that grow up to one or two metres in a year, compare the structure of the two kinds of plants. It’s impressive, really, but they’re a nightmare to keep small. Check out this overgrown Cypress hedge in Plymouth that made national headlines.