Prevent Problems with Leyland Cypress

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, as we have planted more of them - problems are becoming apparent. Over use of this plant and improper site selection and planting have led to disease problems with Leyland Cypress.

Fungi cause canker diseases on Leyland cypress

 Cankers are infected wounds on limbs and branches that may ooze infectious sap. Leyland cypress can get two canker diseases.

Bot canker kills individual branches in the tree.  The foliage may turn grey-green before it dies.  The dead branch will have darker bark and will have a sunken canker where the dead part of the branch begins.

Limbs infected with Seiridium canker turn yellowish and then brown to grey 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.

There is no spray to control these diseases.  These 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.

Dry 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 these canker diseases. 

Prevent disease problems with proper site selection and care

Water plants deeply once every 7 – 14 days during drought.  Wet soils 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. Water this long each time. Soils 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. Run soaker hoses once every 7 - 14 days in dry weather. Turn them on just long enough to wet the soil twelve to eighteen inches deep.

Leyland cypress planted near paved areas, 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 soils 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. 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 getting sick 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 apart.  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 disease.

If your Leyland Cypress already has these diseases …

First cut out the dead limbs.  Be very careful to cut way back into good live tissue.  Cutting diseased limbs and then good limbs may spread the disease.  While pruning you can periodically clean your shears with a towel dipped into rubbing alcohol. We generally do not cut the main stem on a Leyland cypress. If you have cankers on the main stem, remove the tree or treat the disease as per these directions and see if the tree recovers.

Finally, use the information mentioned earlier to find out what needs to change about the way we are growing the plant.  The main problem is often improper watering.  Solving tree problems often comes down to watering and root care since there is generally little else we can do for trees.

Other issues with Leyland cypress

Leyland cypress grow quickly but people plant them in areas too small for their mature size.

All Leylands are propagated by cuttings. Some cuttings do not root well and these trees are prone to be blown over in heavy winds.

Consider these issues when you plant

Avoid plants like Leyland cypress and Japanese cedar (Cryptomeria) if you cannot give them the care and conditions discussed today. Other plants may give you the same results without the potential problems. Consider selecting one of these alternatives. However remember that all plants have certain requirements. Match the plant to the site in terms of size, sunlight, soil type, irrigation and care required.

Possible alternatives to Leyland cypress

See this publication for details on size, growth rate, site preferences, etc. of some of these -

http://pubs.caes.uga.edu/caespubs/pubcd/B625/B625.htm

‘Green Giant’ Thuja                                          ‘Foster’s’ holly

‘Little Gem’ magnolia                                        ‘Bracken’s Brown Beauty’ magnolia

Lusterleaf holly                                                 ‘Nellie R. Stevens’ holly

Osmanthus (tea olive)                                       Eastern red cedar (good option but growth rate can be slow)

Kevin Ong, Texas AgriLife Extension Service, Bugwood.org