As we said before, you are going to want to select the plant to fit the environment rather than the other way around. The range of temperature in which various house plants flourish varies a great deal. Some, such as the majority of Begonias, Primroses and Geraniums, will live best in a comparatively cool setting where the temperature ranges between 50° and 60°; while others, such as the increasingly popular African Violet, whose natural habitat is the jungle of East Africa, prosper at room temperature as high as 70° to 80°.
In almost every home the thermostat is arranged so that the furnace is turned down after a certain hour every night, and as a result the temperature plummets. Unless the drop is extreme and the night time temperature desperately cold, this is nothing to worry about. Even during their blooming seasons, plants in their natural habitat are used to a 10° to 15° temperature drop when the sun goes down, and so they do not react violently to a similar situation indoors. If the indoor temperature falls too low, say 25° to 30° below the normal daytime heat, then it is best to rig some kind of protection for the buds and the foliage of your plants. A tent made out of newspaper or an old piece of burlap will do the trick and act as a blanket until the morning when the rays of the sun (and the heat from the furnace) will again warm up the room.
Because house plants are almost always kept near the window, you must be careful to see that the frame is tight against the sash, or that the cracks are guarded with weather stripping. Often the wall in which the thermostat is set will be comfortably warm while over by the window the temperature will be several degrees cooler. This situation arises most frequently with casement windows which tend not to shut completely. If there is no convenient method of stopping these local drafts, one solution is to arrange your pots on a table provided with casters that can be moved away from the windows at night, and rolled back in the morning.
On the other side of the coin there is the problem of overheating. Although it is doubtful that many house plants suffer directly from an excess of heat, they are certainly affected by the low humidity that always accompanies it. In the winter, the outdoor humidity is generally lower than it is in summer, and central heating tends to dry the air even more. Next to light and proper soil, there is nothing more important to the well-being of plants than moisture, and this goes for the humidity in the air which they absorb through their foliage as well as for the water they take in from the ground through their root structure. There are a number of ways of combating the lack of moisture in the air.
If you care to spend the money you can buy a free standing humidifier which has a humidity thermostat and keeps the moisture content of the air around it at a constant point. A much less expensive and almost equally efficient method is to attach evaporating pans to the radiators, keeping them filled with water at all times. If your plants are clustered around a window below which there is a radiator you can set them in a pan kept filled with a one- to two-inch layer of pebbles, and in which the water is kept just below the top of the pebbles. This pan also acts as a drain for any excess water in the pots.
Most plants will also benefit from having their foliage sprayed lightly every now and again. Once or twice a week is sufficient and it accomplishes three separate purposes. 1) It provides moisture to the foliage dried out by low humidity; 2) it cleans the leaves of accumulated dust; and 3) it helps keep the leaves free of insects. There are many makes of bulb sprayers on the market (see Chapter 2), or you can use an old Flit gun or even a perfume atomizer. Don’t spray the leaves of the African Violet or any other of the varieties of plants with hairy leaves. It will leave white spots on their foliage, and will tend to hasten decay of the leaves.
Remember, your plants are adaptable. They will prosper with reasonable care.