Garden Column for the Salisbury Post

Darrell Blackwelder

June 24, 2004

     Leyland cypress is generally considered the perfect shrub for urbanites crowded in housing developments. Alas, these shrubs have become over planted, sharing the same fate as red tipped photinias. Red tips are generally never planted because of entomosporuium leaf spot that rapidly defoliates and eventually kills the shrub.

     Leyland cypress is rapidly approaching red tip’s fate. Leyland cypress is an intergeneric shrub of two separate genera; a cross between Monterey cypress Cupressus macrocarpa and Alaska cedar Chamaecyparis nootkatensi that originated in England in 1888. Through careful selection, plant breeders discovered that the unusual cross provided nurserymen the perfect narrow screening plant with extreme hybrid vigor. However, over planting over the years has made the plant very susceptible to insects and diseases.

     Bag worms are now a serious problem that first appeared about 5 years ago.  Moth larvae hatch in the early summer forming a protective cocoon. Scores of larvae feed during June and July with the potential of defoliating the shrub. These insects can completely defoliate a shrub in a matter of days easily killing the plant. Sprays of Sevin or Thuricide in the early larval stage easily kill the insect. Those with a few larvae can hand pick them off the shrub. As the insect matures, they increase in size and become and resistant to insecticides. As the summer progresses, the larvae become very difficult to control.  After these pupate, they are impossible to kill. Large shrubs can be difficult or in some cases impractical to spray.

     More recently, fungal diseases have become a problem on Leyland cypress. Root rots, needle blights and canker diseases are taking their toll on the shrubs. There are 6 known fungal diseases that easily kill Leyland cypress.

     Phytophthora root rot and Armillaria root rot are two of the root diseases that are killing them in Rowan County. Plants decline slowly and eventually die. Unfortunately, there is no control for these diseases. Removal of affected plants is the best solution.

     Cankers are fungi that affect both trunks and limbs causing limbs to dieback.  Prune out the infected portions. Avoid heavy fertilization and water during dry periods. Mulching will help, but avoid excessive applications. Spacing plants no closer than 5 feet to allows for good air movement reducing incidence of fungal disease problems.

     Anyone with these shrubs during the ice storms a few years ago can testify that ice and Leyland cypress do not mix. Tall weak branches make them susceptible to damage from both ice and high winds.

     Those considering planting a hedge or replacing dying Leyland cypress should consider alternatives such as the new arborvitaes or Cryptomeria japonica.  Hollies such as “Nellie R. Stevens” and Greenleaf holly do well as border or screening materials.    

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com , e-mail Darrell_Blackwelder@ncsu.edu