The more experienced members provided insight regarding the severity of the winter and the problems it brings to people attempting to grow in a greenhouse or modified structure. As the discussion progressed, here is some of the advice given to novice and experienced growers of Phals. Because the Phals are nearly all equatorial and low altitude growers, they have very low tolerance of cold weather. The temperature shift between day and night should probably not be excessive, and the night temperatures should never be allowed below 50 F. Water carefully to avoid getting water in the leaf crown. Water should feel warmer than the ambient temperature.
Cold water causes stress and cold water standing in the crown causes crown rot and fungus.
Be alert for signs of leaves developing a transparent appearance, soft texture, loss of lower leaves, or black in the center leaves and crown. The former are progressive symptoms of damage caused by exposure to cold extremes in air temperature and water. A consideration in the greenhouse is thermal layering or changes in temperature based on distance from the heat source and floor. All orchids are sensitive to reduced humidity caused by artificial heat. Electric heat dries the air and reduces the humidity, gas heat can also complicate the dryness by contributing fumes and carbon monoxide.