Leyland Cypress (Cupressus x leylandii) are a popular tree/shrub, commonly planted for its rapid growth and dense evergreen canopies providing year round screen. In southern oregon, these trees can grow to an average height of 40-50 feet with a canopy spread of approximately 25-30 Feet. A species cultivated from Monterey Cypress (Cupressocyparis macrocarpa) and Alaska Cedar (Chamaecyparis nootkatensis). Leyland Cypress prefer moist well draining soil and require annual pruning to maintain a hedge or shrub size and optimize any shade or privacy goals. Often, the goals are established, a tree is planted, but no long term management plans are created. For some tree species in the right conditions this could be ok but for Leylands it usually results in large overextending canopy with a higher likelihood of failure, or a significantly stressed or declining tree that could be costly to remove once dead.
If you plant Leyland Cypress it’s a good idea to establish how tall the canopy will need to be to achieve your goals like privacy or screen. Once the tree reaches this size consider pruning periodically to manage the canopy and reduce the chance of branch failure. Irrigation is also important. Make sure your Leyland’s are watered thoughly during the summer. We suggest using Arborist woodchips as mulch to help retain moisture, regulate soil temperature, and improve soil biology further improving the growing conditions for any tree.
If you have large mature Leyland Cypress and your unsure how to manage them, contact your local ISA Certified Arborist to evaluate your trees and provide a management plan tailored to your specific situation. Often irrigation practices can be adjusted to maintain tree health while pruning addresses structural characteristics and mitigates any risk to your property.
When Leyland Cypress do not receive sufficient irrigation, they become severely drought stressed making them highly susceptible to pests like the cedar bark beetle (Phloesinus species) and numerous diseases such as Cypress Canker (Seiridium cardinale) that can be fatal.
References:
https://depts.washington.edu/hortlib/keyword/trees-diseases-and-pests-washington/
https://pnwhandbooks.org/plantdisease/host-disease/cypress-cupressus-spp-canker