Most of our houseplants enjoy temperatures in the house that are comfortable for us. A range of 60 degrees at night to 75 degrees in the daytime is suitable. Now, with the thermostat lowered and temperatures not as comfortable for us as we might like, what about the plants? Actually, most of them won't suffer too much. And, there are some means by which you can relieve the stress.
If you have lowered the temperature from a customary 70 or 75 degrees (or even more) in the daytime to 65 daytime and 55 at night, as we have been asked to do, some of your plants may lose leaves or at least go into a "holding pattern" of no growth as they react to lower temperature.
However, if the temperature remains below 60 degrees for any length of time, plants will be checked in growth and may not recover. If your office is maintained at 40 to 45 for long weekends, plants will suffer, especially flowering species. Tropicals such as dracena, schefflera, philodendron species and ficus species will be adversely affected.
Let's look at some of the conditions you'll encounter and consider what you can do to alleviate the situation.
Indoor temperatures can vary as much as 20 degrees in the same room at the same time, from near the window to near the radiator. Check on this and arrange warmer accomodations for the plants, if need be.
Plants situated close to windows will experience a lower night-time temperature than plants elsewhere in the room. In extremes of cold, such as we have had recently, it is advisable to move the plants away from the window, draw curtains between plants and window panes, or place cardboard or newspaper between plants and window panes, especially at night.
Leaves should not touch window panes. The entire plant may not be frozen but that leaf will be lost.
If you decide to move plants away from windows to a warmer spot, don't get them in front of hot air radiators or space heaters. Remember, too, that heat from incandescent blubs such as those in table and desk lamps can burn leaves.If you set a plant under such a light, the plant is close enough when you can feel the warmth of the light on the back of your hand.
Avoid drafts or blasts of cold air from doors frequently opened. Move plants away from entryways where there is continuous traffic.
With lower temperature and slower plant growth, less water is required to maintain the plant. Watering will probably need to be reduced.
For specific plants: Most foliage plants will not suffer with temperature at 50.55 degrees at night. Geraniums, miniature roses, strawberry begona (saxifraga), ivy, wandering jew, and some cacti can be even cooler. For gloxinias, African violets and other gesneriads, the temperature should never be less than 60 degrees at night. Perhaps you can contrive a protective enclosure where these plants will have the benefit of any warmth your heating system provides during the night.
Optimum growth for a plant in relation to temperature depends on the plant's place of origin. Most of our indoor plants come from warm climates but from elevations that are cool at night. When lights go out at night in home and office, a drop of 10 degrees is welcome; in fact, it is needed because the growing processes that go on during darkness do not require as much warmth as daytime functions. When a plant is dormant, that is, resting or not actively growing, a temperature of 60 degrees at night is adequate. Most of our foliage houseplants are not actively growing during the short, often sunless, days of winter. Consequently, unless the low temperature is excessive and of some duration, your plants will just sit there and wait for things to warm up as the rest of us have been doing for the past few weeks.