The Leyland cypress is commonly used as a wind break or hedgerow, which is precisely why it is subject to winter damage. The reasons for planting it in these locations -- blocking the wind, creating privacy or other type of barrier -- contribute to exposing the trees to the very conditions that can lead to winter damage. High winds, strong sunlight in below-freezing temperatures, snow and ice can prevent the Leyland cypress from being able to maintain an ample flow of water during the winter months and can lead to damage or even death of the tree.
About Leyland Cypress
The Leyland cypress is a fast-growing evergreen tree, adding 3-to-4 feet of height annually. Its mature height is between 60-and-70 feet, but it has been known to reach 100 feet. The leaves are fine, feathery needles that give it a delicate appearance. The tree is tolerant of full sun to partial shade and both alkaline and acidic soils.
Winter damage is evident when the needles of evergreens such as the Leyland cypress turn brown from the tips. It is called leaf or needle desiccation. Desiccation occurs when plants lose water through transpiration faster than roots can draw in moisture from the soil. It is prevalent in the winter because that it when the soil freezes, making water unavailable to the roots. In spite of cold temperatures, bright sunshine can actually heat the leaves internally, causing transpiration or water loss.
In addition to the browning of needles at the tips, Leyland cypress trees may display other symptoms if the case is more severe. The browning or drying out can move inward and affect branches and twigs as well. Needles and branches take on a burned look, and needles can begin to drop. In severe cases, the drying out can kill the tree.
In some cases the browning is a result of cracked or split branches caused by the weight of ice or snow or from severe winds. These damaged branches cannot supply water efficiently to the tips beyond the split. In cases where desiccation is the primary cause, contributing factors can be the tree's proximity to reflective surfaces such as concrete, a white house, snow cover or any surface that may intensify the sun's heating properties. Symptoms may be worse for trees with strong sun or wind exposure, particularly on the side of the tree that receives the brunt of the sun or wind.
There is no actual treatment for winter damage on Leyland cypress tree. Before any steps are taken, the damaged tree should be allowed to begin spring growth. Often, if the damage did not injure leaf nodes, new growth will emerge, and the browned needles will drop off naturally. If new growth does not emerge, the branch was severely damaged and should be pruned away about one-fourth of an inch above where green color is still visible. Leyland cypress trees are tolerant of heavy pruning, but if more than one-third of the tree is damaged, the tree may need to be replaced. Selecting sites that do not expose the Leyland cypress to conditions that lead to drying out can greatly reduce the risk of winter damage.