‘Castlewellan Gold’ is a golden Leyland cypress with yellow‑green new growth that deepens to lime in summer, providing year‑round colour. Slightly slower than the type (60 cm yr), it still makes a quick hedge or column to 15 m if unpruned. Full sun intensifies colour; otherwise, culture matches standard Leylandii—any free‑draining soil, coastal wind tolerance and hardy to −20 °C. Clip lightly 2–3 times a year to keep dense and bright.