Leyland cypress (Cupressus x leylandii) is a hybrid species resulting from a cross between the Alaskan cedar (Chamaecyparis nootkantensis) and the Monterey cypress (Cupressocyparis macrocarpa). It is a popular choice for privacy screening because of its extremely fast growth rate - quickly growing 40-60 feet high and over 15 feet wide. In prime growing conditions, they can reach 100 feet tall and 50 feet wide.
In the Pacific Northwest, Leyland cypress is often an inexpensive and well-intentioned planting, but quickly takes over yards and driveways, damaging nearby fences, shading out gardens and overwhelming urban landscape. Craig Bachmann, Lead Arborist for Tree133, often refers to this as "the alligator in the bathtub." Before you know it, the tree is out of control.
Should I plant a Leyland Cypress hedge?
What seems to be an inexpensive and easy privacy screen will need annual trimming to maintain the hedge form. These trees are aggressive growers so a small upfront investment to plant may become a significant investment of time and dollars to maintain.
Can't we just top the trees once they get too big?
Topping actually encourages faster lateral growth and a "candelabra" shape with multiple tops that are difficult to contain. Topped Leyland cypress develop large, upright limbs that more prone to failure. Read more from the University of Washington Elisabeth C. Miller Gardening Knowledgebase.
Can anything be done to help my Leyland cypress trees that are bare and "browned out?"
Leyland cypress are generally very tolerant of hard pruning. However, pruning that removes all green foliage from a limb will result in a dead stub. Like most conifer trees, Leyland cypress do not have "latent buds" that begin growing in response to pruning. Instead, new foliage grows from the tips. Unless these trees are contained - hedged or hand pruned - appropriately at a young age and then regularly maintained, these interior "dead zones" become visible and a lasting problem.
What happened to my Leyland cypress under the wires?
Trees that are growing into and around wires may be cut back hard during city safety clearing. Seattle City Light will notify homeowners of upcoming pruning.
Contact the certified arborisits at Tree133 with questions about how to manage and maintain trees on your property.