The Leyland Cypress is a hybrid evergreen tree, popular in landscaping for its dense foliage and rapid growth, making it an excellent choice for privacy screens and windbreaks. It is a cross between the Monterey cypress and the Nootka false cypress, resulting in unique vigor and adaptability. The primary challenge for homeowners is managing its tendency toward immense size, which can quickly overwhelm a residential property. Understanding its natural growth pattern is essential for maintaining a manageable and healthy tree.
Understanding Growth Rate and Mature Height
The Leyland Cypress is one of the fastest-growing evergreen trees, capable of adding significant height quickly. Under optimal conditions, a young tree can grow between three and four feet each year, which is a key reason for its popularity as a quick-forming screen. This rapid vertical growth continues for many years.
The maximum height the tree can reach depends heavily on whether it is cultivated or left to grow naturally. In a managed landscape setting, most Leyland Cypresses are maintained at a height between 30 and 50 feet through regular pruning. Unmanaged trees can easily reach heights of 60 to 70 feet, and documented instances exceed 100 feet in height.
The tree reaches maturity when its growth rate begins to slow down, which typically occurs after many years. While a growth rate of three to four feet per year is common in youth, this rate generally decreases as the tree approaches the 50-foot mark. For practical purposes, the tree is considered mature once it has reached the height the homeowner is willing to maintain.
Environmental Conditions That Impact Size
The ultimate size a Leyland Cypress attains is heavily influenced by the quality of its growing environment, which dictates its vigor and longevity.
Sunlight and Soil Requirements
Maximum growth is achieved when the tree receives full sun exposure, meaning at least six hours of direct sunlight each day. Trees planted in partial shade will still grow, but their vigor and density will be reduced. Soil quality plays a significant role, with well-drained, fertile soil producing the best results. The Leyland Cypress is highly sensitive to overly wet or dense soil, which can lead to root rot and premature death. Consistent moisture is necessary for fast growth, but overwatering is detrimental and will severely limit its ability to achieve its full potential size.
Hardiness Zones
The geographic location, specifically the USDA hardiness zone, dictates the tree’s overall lifespan and ability to thrive. Leyland Cypresses perform best in Zones 6 through 10, where temperatures do not dip too low. Growing the tree outside of its preferred zones can stress the plant, reducing its growth rate and maximum achievable height.
Techniques for Controlling Leyland Cypress Height
Due to the tree’s rapid growth, managing its height requires proactive and consistent intervention throughout its life. The most effective method for maintaining a manageable size is regular shearing, which should begin when the tree is young. Shearing involves trimming the new growth on the sides and top, encouraging the development of dense, thick foliage.
Once the tree has reached the desired height, the central leader, or main vertical branch, should be shortened to approximately six inches below that final height. The subsequent new growth will then thicken the top of the tree, allowing the height to be held consistently with repeated annual trimming. For established trees, trimming the top and sides up to three times during the active growing season is often necessary to prevent rapid height addition.
It is important to understand the distinction between proper shearing and improper “topping,” which involves cutting back into the old, leafless wood. Leyland Cypresses do not reliably produce new growth from bare, older branches, so topping can leave permanent, unsightly gaps or cause the top of the tree to die back. Reducing the height of an overgrown hedge by more than one-third is stressful and should be avoided, as it compromises the tree’s health and appearance. The best time for height reduction and trimming is typically between April and the end of August, avoiding late-season pruning that could stimulate new growth vulnerable to winter damage.