Leyland cyprus trees
I have a row of Leylands that are about 30-35 feet tall and they are used as a barrier between housing lots. The side facing me gets plenty of sun and the trees look like they are thriving but the other side is in the shade of other trees all the time and the branches are completely brown with no growth on them what so ever. My questions is simply, should I cut these dead branches off to strengthen the trees? If so, how far back close to the trunk should I cut? I have probably been getting away with tree murder so far and no longer want to press the issue. Thanks, Bob R. Any information you can supply will be very appreciated.
Certified GKH Gardening Expert
Hi Bob, I'm Don, a California arborist but familiar with Leyland cypress and the type of issue you present.
You are surely correct in your assessment of the dense shade being the cause of the dead/dying branches at the rear of the row. Pruning off the dead branches is not essential and won't necessarily strengthen the trees, and may in fact increase the weight distribution to the outside. I worry that with a one-sided foliar canopy growing heavier all the time, that when the soil is wet and the wind blows, you could get trees uprooting and falling due to the weight distribution.
In this case, since it's out of sight there is no appearance value to removing deadwood. Cleaning deadwood us usually beneficial for avoiding habitat for bark beetles and wood decay fungi.
Also, there is good reason to try and open to some sunlight penetration to allow the trees to put out some new growth on the back side. That may involve thinning the other trees in the back area too.
If you do remove branches that you confirm as entirely dead, (inflexible and no green growing layer when you slice off a thin amount of bark), then prune all the way back to the branch collar, just out a little from the parent limb or trunk.