Emerald arborvitae is the slow-growing tree. It is best ideal for the natural hedges. Usually it was 10-15 feet tall and 3-4 feet wide. Green Emerald Arborvitae takes 6 to 9 inches of growth in one season. To maintain proper health, remove dead leaves and regular pruning. The treatment involves handpicking pests, pruning. It may turn brown especially if it is stressed.