Leyland cypress, known botanically a Cypress leylandii, is an evergreen tree with the profile of a classic, pyramidal Christmas tree. While we often think of evergreens as forest trees that live in at least partially shaded conditions, this is not the preferable setting for leyland cypress. The tree is fast growing and requires full sun to maintain its foliage and even its natural structural form. Overhead shade as well as shade-created crowded lateral plantings can do more harm to the tree than the average person might imagine.
Leyland cypress trees require a full sun exposure, year-round, to grow at their optimal rate and produce the lush, dense, full pyramidal canopy they are known for. Any consistent shade will begin to reduce and thin their flat, scaly foliage. The foliage can brown and drop, slow its growth or stop growing entirely. In addition, limbs that receive little or no sun will weaken and may eventually die back entirely due to a stall in photosynthesis activity.
Spacing of Plants
Leyland cypress tree grow to a mature spread of 25 feet. When the trees are young and planted too close together, the lower branches become entangled and shaded. When the wider lower branches and limbs of the tree are shaded, they can become defoliated and die back entirely. This permanently alters the shape of the tree, raising the canopy height and reducing the screening effect for which the tree was likely planted in the first place. Lateral overcrowding also spurs problems with poor air circulation, creating conditions ripe for fungal diseases and other pathogens. Trees planted too closely together should be thinned by transplanting or removal to allow more distance between trees, somewhere in the range of 25 feet between each trunk.
Leyland cypress trees grow to reach a height of 60 to 70 feet at maturity. While considered a fast growing species, they do not reach this height overnight. When small, the tree can often be planted where overhead shade or cast shade is problematic. Planted too near a house, overhanging eaves and taller trees can all reduce the sun the tree receives, thereby altering its growth and form. When pruning of nearby trees is not a full solution, transplanting the tree to a location where it can bask in the sun from every angle, throughout the day, is recommended.