For most house ferns normal room temperature ranging from 65 to 75 degrees is ideal. High humidity is essential along with warmth. Stand pots on trays of moist pebbles, and suspend saucers of water under hanging baskets at all times. When ever room temperature remains above 70 degrees for more than a day or two, increase the ny mist spraying the foliage at least once every day. Spraying should be done very carefully, however, since drops of water left on the fronds of certain kinds of ferns can mark or damage them. Spray with tepid, not with cold water, and hold the sprayer 2 feet away from the plant. At a distance the air around the plants becomes moist, while only a fine mist falls on the plant itself.
If, for any reason, indoor temperatures are permitted to fall below 65 gegrees in winter, there is no cause for concern. Virtually all ferns can tolerate temperatures down to about 50 degrees. As the temperature falls, growth will slow down, and it will cease alltogether at 50 degrees, but without impairing the health of the plant. The fern will simply take a rest until the temperature rises again. During any such rest period watering should be drastically reduced, but the plant still requires high atmospheric humidity to prevet the fronds from wilting.