Croton (Codiaeum variegatum pictum) is a true tropical plant from Malaysia and India, so it thrives in sunny locations where temperatures hit the 80s during the day and stay at least in the high 60s at night. Cold drafts of air cause plants to drop leaves. Investigate the air seals in your garden room. Do you have cold air that's blowing onto plants? During the summer, even central air-conditioning could cause the problem. Low humidity can also cause leaves to fall. Boost humidity around the plant with a room humidifier.