The ‘X’ preceding its Latin name ‘X Cupressocyparis leylanii‘ designates Leyland cypress as a hybrid of two distinct genera, namely Monterey cypress and Nootka cypress. (Those who consider the parents to be two species of the same genus know Leyland cypress as Cupressus X leylandii.) The many cultivars combine desirable qualities of both parents, but also innate weaknesses.
Rows of Leyland cypress grow fast to become densely evergreen windbreaks or informal screens within only a few years. However, they are very susceptible to cypress canker, and are likely to succumb within twenty five years or so. Farther inland, they may not last half as long. That may be quite acceptable for temporary windbreaks in front of slower but more permanent shrubby trees.
Common Leyland cypress develops a distinctly plump but conical form, with slightly grayish foliage. Most other cultivars are more columnar. Foliar color ranges from bluish green to gold. The tiny scale leaves are densely set in flat sprays. Healthy trees can get nearly thirty feet tall in ten years. Most stay lower where exposed. Crowded trees that live long enough exceed a hundred feet tall.