By Eddie Ayers, County Extension Agent, March 9, 2015
Leyland cypress is a popular, fast growing hedge or border tree reaching heights of 50 to 100 feet and widths of 20 to 30 feet. Though Leyland cypress originally appeared pest resistant, problems have recently become apparent. Over use of this plant, improper site selection, improper planting, and stressful weather conditions have led to two disease problems. They are cankers and root rot.
Cankers are infected wounds on limbs and branches that may ooze infectious sap. The trees get the canker because of fungi entering the tree. Leyland cypress can actually get two canker diseases. Botryosphaeria Canker is one type and it is commonly called Bot Canker which kills individual branches in the tree. The foliage may turn rust colored before it dies. The dead branch will have darker bark and will have a sunken canker where the dead part of the branch begins.
The other canker is Seiridium Canker. Limbs infected with Seiridium Canker turn yellowish and then brown when they die. Limbs often die back from the tips. The cankers on the main stem are sunken, reddish and ooze sap profusely. There can be many cankers on a limb and unfortunately, there is no spray to control these diseases. The diseases enter wounds and are worse during stressful conditions. The main control is to keep the plant in good health so it can resist these diseases. Extreme weather and improper watering can be big factors in the spread of these diseases. Plants with roots that get too wet or too dry are more likely to get either these canker diseases or root rot.
If the weather turns into a drought, water plants deeply once every 7 – 14 days and wet the soil to a depth of twelve to eighteen inches when watering. This will probably require one inch of water. If you use sprinklers, put a pie pan or tuna can under the sprinkler and turn it on. Time the sprinkler to see how long it takes to apply one inch of water and water this long each time. Soil must dry out between watering or roots may die. Avoid wetting the leaves and limbs when you water. Soaker hoses are better because they keep the foliage dry, which may reduce disease problems.
Selecting the proper planting site will go a long way in helping prevent disease problems. Leyland cypress planted too close together, near paved areas, next to walls or other heat reflecting surfaces may need special care in watering and planting to get established and to grow well. Plant Leyland cypress in well-drained soil in sunny locations. Mulch them after planting but mulches should be no deeper than two to four inches. Apply mulch from the base of the tree out to several feet beyond the reach of the branches. Because it holds in water, do not use landscape fabric unless the soil is very well drained. Do not pile mulch against the base of the plant.
Do not plant Leyland cypress in wet soils or poorly drained areas. They may respond to wet feet by developing root rot or dying. Check soil drainage before you plant or if the tree has problems. Dig a hole about a foot deep and wide. Fill it with water. If it takes longer than three hours for the water to drain out, the soil is probably poorly drained. Do not plant Leyland cypress closer than eight feet. As the plants get big enough for the limbs to touch, remove every other tree. As the limbs rub together, they cause wounds that can be infected by the fungi which causes the canker diseases.
If your Leyland cypress already has these diseases, first cut out the dead limbs. Be very careful to make cuts into good live disease free tissue. Cutting diseased limbs and then good limbs may spread the disease. While pruning you can periodically clean your shears with a towel dipped in rubbing alcohol. Leyland cypress generally does not respond well to cuts on the main stem, but if you have cankers on the main stem, remove the tree or cut below the canker and see if the tree recovers.
Use the information mentioned earlier to find out more about your Leyland cypress. Nothing can be done about the weather, but you can lower the stress on the tree. For more information view the on-line publication Diseases of Leyland Cypress in the Landscape Bulletin 1229 on our web site at http://www.caes.uga.edu/extension/gilmer/. Finally, because of the problems with Leyland cypress, you might want to consider using a different plant.
For more information, contact me at the Gilmer UGA Extension office.