Houseplants: Improving the Plant Environment
There are many ways to improve the environment indoors so that plants will really thrive. The best way to increase humidity in winter is by a central humidifier, although a portable humidifier in the plant room will also help a lot. Other aids include pans of water placed under radiators and shields to deflect the hot dry air away from the plants. Moist pebbles in a tray will humidify a whole group of plants. Pebbles can also be used in individual saucers placed under each pot. Often the perfect solution to the problem of high heat an low humidity is turning off radiators near the plants and using an electric heater in the room. In hot weather, protection from the direct blast of an air conditioner is imperative and plant rooms should not be kept abnormally cold.
Improving light intensity may simply involve adjusting blinds or drapes, or trimming shrubbery outside the window, or keeping the window glass clean. Overcrowded plants will cut off light from one another, and hanging plants may suffer from lack of light if hung too high. Where good natural light is not available, electric light can be used. Even where ample natural light is available in summer, supplementary artificial light may be needed in winter.
A pair of 40 watt fluorescent lamps with a reflector will light a 2 by 4 foot area sufficiently to promote healthy plant growth. Such a unit can be used either for supplementary light in a window that receives no direct sunlight or to supply the full quota of light. In the latter case, lamps are kept on 12 to 16 hours daily for African violets and 10 to 12 hours for foliage plants. Fluorescent daylight lamps, or fluorescent lamps made specifically for plants, or a combination of the two may be used.
Incandescent bulbs may be used as a light supplement, but they are less suitable because they are hotter and their light is more concentrated. Foliage plants benefit from the light of a decorative lamp if not kept too close to the bulb.
Spotlights may be of some help, if kept at a distance.
A terrarium, a fully enclosed container made mostly of glass, provides a means of creating a tiny landscape in an island of humidity, even in the driest room. The addition of a fluorescent light makes it completely independent. Small tropical plants thrive in such a miniature greenhouse, but woodland plants can also be used, if temperatures can be kept cool. An old fish tank makes an ideal terrarium, but fish bowls and brandy snifters will also serve the purpose.
A window greenhouse is a boon to the indoor garden. Since it projects from the building, light reaches the plants from three sides and from above, instead of from only one side. The light in a window greenhouse may be more than double that of the windowsill light. (The light intensity one foot back into the room may be about half that at the windowsill.) Glass shelves are good because they allow light to pass through to plants on lower shelves. Mesh shelves are even better because they permit the passage of air as well as light.