Leyland cypress trees are a very common and popular landscaping plant. They are planted by people all over Georgia. However, there are a couple of issues that are commonly seen in Leyland cypress trees. Let’s talk about Leyland cypress trees, what some of those issues are, and what steps you can take to reduce the chances of your Leyland cypresses getting diseased, because recently I have gotten a lot of calls from people with questions on their Leyland cypress trees.
The biggest issue that people have right now is that their trees are turning yellow and brown on the inside. This is due to the mild winter that we had earlier in the year. Leyland cypress trees prefer a climate that is colder than what we have in the Georgia Mountains. When plants don’t have the climatic conditions that they prefer it makes them much more prone to stress. The tree’s natural response is to start to drop the needles that are closest to the trunk. These needles turn yellow and then brown before falling off. The best thing to do if you see this happening is to make sure that you are watering your trees during a dry spell. Leyland cypresses have a shallow root system, which makes them prone to drought stress.
Another thing to keep in mind is that these trees have an effective lifespan of 15-20 years. So, if your trees are that age and don’t look healthy, they probably aren’t going to improve significantly.
The two canker diseases that Leyland cypress trees get are Seiridium and Botryosphaeria canker. Seiridium canker is the most common and destructive of the two in Georgia. The symptoms from both diseases look very similar. You will see individual branches begin to die off. Sometimes you’ll see resin in spots on the branches because of the cankers. These cankers are essentially suffocating the branch, leading to the branch turning brown. Once a tree has been infected the best treatment is to remove the dead branch and dispose of the branch.
Stressed trees are going to be more susceptible to cankers. During times of drought, trees that are already infected will spread the disease much more quickly. Ice damage and spring freezes can create wounds where infection is able to occur. Trees that are near buildings that reflect sunlight will also be more stressed. Unfortunately, with canker diseases there is not a fungicide that can be used to eliminate the pathogen.
Passalora needle blight has become more common as well. This is a disease that will cause the needles to drop off of the tree, working its way up to the top. It is possible to spray for passalora, but it is not practical. The spray must be applied to the whole tree multiple times a year. If you have a 40 foot tall tree, that is very difficult.
Try to keep plants from becoming stressed by laying mulch around their base. This will increase the moisture retained by the soil, and suppress competitive weed growth. During dry, hot summer days, water the trees if the soil has become dry. If trees are extensively damaged by cankers or needle blight, then they will need to be removed. When planting Leyland cypress make sure to dig out an area 3-4 times larger than the diameter of the root ball. This will improve soil drainage, resulting in your trees being less stressed and less susceptible to root rot diseases. In addition, plant trees at least 15 feet apart. A common issue is that Leyland Cypresses are planted very close together to make a better screen. This also invites disease and increases the rate of decline.
There are some alternatives to Leyland cypress trees that are better adapted to our environment. Green Giant arborvitae and Arizona cypresses are both trees that serve the same purpose in landscape and are more disease resistant. For anyone planting trees as a barrier or screen, I would encourage them to look into these alternatives.
If you have questions about Leyland cypress please contact your county Extension Office or email me at Jacob.Williams@uga.edu.