Leyland cypress is an accidental hybrid, the result of two North American conifers cross-pollinating on a Welsh estate in the 1880s: Monterey cypress from the California coast and Nootka cypress from the Pacific Northwest. The combination produces a fast-growing, densely needled tree that can reach three feet of growth per year in its early decades, hit 50 feet within 15 years, and eventually top out near 70 feet. The blue-green foliage arranged in flat sprays is genuinely attractive, and the symmetrical form requires no training. For those reasons, it was planted by the millions across the American South and Mid-Atlantic as a privacy screen and Christmas tree crop.

The problems are well documented by now. Shallow roots make large specimens prone to toppling in storms. The same density that makes it attractive as a screen also traps moisture and restricts airflow, creating ideal conditions for Seiridium and Botryosphaeria cankers, which kill entire branches without warning and have no cure. Armillaria and Phytophthora root rots follow drought stress with similar finality. Bagworms can strip a tree in weeks. Most Leylands in the Southeast show serious decline by their third decade, which is a short lifespan for a tree of this ambition. Better alternatives exist for screening: native hollies, Eastern red cedar, and cryptomeria all offer similar scale without the disease burden.