My Leyland cypress trees are 5 years old and until three months ago they were beautiful. All of a sudden, they are turning yellow from the inside out. My soil is sandy and well-drained. What is happening?
The Gardener’s Answer
Hello, Kathleen in Virginia: It sounds like your Leyland cypress (Cupressocyparis leylandii) are well-established evergreens. It is perfectly normal that these plants shed some of their inner foliage. This is especially true for the Leyland cypress because they are such fast growers that they need to drop some of their foliage in order to make room for new growth. Although this is a natural process it typically does not happen this time of the year. These evergreens do have their share of problems, including bagworms and various fungal diseases. You should take a sample of the yellow foliage to your County Cooperative Extension Service to rule out any insect or disease issues. They will be able to give you a positive diagnosis as well as control methods if needed. Leyland cypress thrive when planted in full sun, at least six hours each day, and demand well-drained soil. Root rot can become a problem if the plants are exposed to excessive moisture, although this does not seem to be a problem in your case. Making sure the space around the plants is free of fallen plant debris is important in terms of not spreading any potential insect or disease problems. Dead plant material is an inviting place for insects to live and potentially over-winter. Without seeing a sample I can only speculate as to what is going on with your evergreens.