Humidity for Houseplants

Although plants don't need as much water in the winter, they do need sufficient humidity. Most homes stay at about 20 percent humidity in the winter, which is fine for cacti, but most tropical plants need 40 to 60 percent for good health. The best and most expensive solution is to install a furnace humidifier (and it's good for people, too). The second-best solution is a portable room humidifier. Place plants next to the unit, and direct the moisture stream right at them.

Misting, however, is the most common humidifying method, and Gardening by the Yard host Paul James uses filtered water at room temperature. He mists three times a day and advises against drenching the plants.

Indoor plants slow their growth or go dormant in the winter. Water them only when the soil is dry to a depth of one to two inches, and use only tepid water--cold water can shock the plants. Cut back or even stop fertilizing, too, since you don't want to stimulate new growth in the winter. For the same reason, don't repot plants until the spring.

Keep houseplants away from heating vents to avoid drying them out too quickly. They should not be exposed to cold drafts, either, especially uninsulated windows and frequently-used doors. It's also good to shelter plants from the lower angle of the winter sun so that they don't receive more light than they need or normally expect .