This article was written by Gail Griffin, Extension Master Gardener Volunteer with North Carolina Cooperative Extension in Lee County.

To get an idea of how many diseases commonly affect Leyland cypress, take a look at the episode of The Andy Griffith Show titled “Barney’s First Car”. After the once over at Wally’s Filling Station, the car needed “plugs, points, bearings, valves, rings, starter switch, ignition wires, water pump, fuel pump, oil pump…”, well, you get the picture. If you have had no issues with Leyland cypress, consider yourself fortunate. Its popularity has led to overplanting the species to the point that diseases are taking a toll on the landscape.

Leyland cypress, X Cuprocyparis leylandii, is a large, extremely fast growing evergreen that has the potential to grow one hundred feet tall and fifty feet wide. It is able to grow in a variety of soils and temperatures. It grows best in full sun in a well-drained location, spaced at least twelve to fifteen feet apart. Two main types of fungus affect the root system. Phytophthora root rot is found in poorly drained soils and usually affects younger trees. Plants may become stunted with sparse foliage that turns yellow, purple or tan. Sometimes cankers or lesions are evident at the soil line. Armillaria root rot results from deteriorating woody materials like tree stumps that have been left beneath the soil. It spreads to newly planted root systems and eventually, the rest of the plant, causing decayed areas on roots and bark. Symptoms include stunted growth, dieback of stems and branches and gradual or sudden death. Mushrooms may be present at the base. Pathogens of both types of fungus can remain in the soil even after the plant is removed. Poorly drained soils can spread the disease to plants nearby.

Three additional types of fungus affect portions of the plant above ground. Seiridium canker can be identified by dark oval lesions on stems and branches. Multiple cankers can form causing dieback. Needles will easily fall by running a

hand along the affected branch. It can spread by open wounds from lawn equipment or pruning tools. It can also be spread by overwatering. In Botryosphaeria dieback, needles don’t readily fall when handled but branches will turn yellow to brown. Cankers will girdle a stem and kill the stem beyond the canker. Passalora needle blight usually occurs during summer months and generally affects one year old growth. It causes needle browning and eventual drop from near the trunk spreading toward branch tips. It will spread upward over time until the only green is on the upper tips.

The decline of Leyland cypress has been as a result of monoculture problems meaning the overuse of a single plant species or cultivar. Plants placed too close together will only hasten the spread of these diseases. Control after these pathogens have reached the plant whether by air, by water or underneath the soil may be futile. Removal of infected branches and stems require disinfecting of tools in between cuts to avoid further spread. If the whole plant has to be removed, do not put another Leyland cypress in its place. Alternatives include Arizona cypress, Japanese cedar and Green Giant Arborvitae. The use of mixed screens is another solution. It involves planting multiple species in small clusters of three or five, or alternate layers to help control the spread of disease from one plant to another. For more information, go to hgic.clemson.edu/factsheet/leyland-cypress-diseases-insects-related-pests/

Other problems with Leyland cypress involve pests including bagworms, spider mites and scale. Also, a cypress weevil may be on the horizon. The list may continue to grow, only time will tell. For now we can only make better choices in replacing them should it become necessary. In case you need a reminder, “…clutch, clutch bearings, clutch plate…”

Gail Griffin is an Extension Master Gardener Volunteer with North Carolina Cooperative Extension in Lee County.