Use Cupressocyparis × cuprocyparis 'Leylandii' when you want a quick, tall evergreen screen with a narrow conical to pyramidal look. You can let it grow into a large specimen or keep it clipped as a hedge for privacy and windbreaks. Expect strong, upright growth and dense, scale-like foliage that stays green year-round.
Plant your Leyland Cypress 'Leylandii' in full sun for best density, but it can handle light shade in many landscapes. Give it room to mature, or plan on regular pruning if you are using it in a confined space. Good air movement and avoiding chronic stress can help reduce disease pressure over time.
Provide average moisture while the plant establishes, then water during extended dry periods. It is often described as relatively drought tolerant once established, but consistent care during heat and drought helps keep foliage full and reduces stress-related problems. It adapts to a range of soils as long as drainage is reasonable.
For screening, space plants with their mature size in mind and prune as needed to keep the hedge within bounds. If you top or shear, do so intentionally and maintain a shape that allows light to reach lower growth so the hedge stays full from top to bottom.