INTENSITY
Here again we find the needs of plants vary and fluorescent-light setups vary accordingly. If possible, measure the light in your growing area. The readings of a photographic light meter—the same instrument you employ in your photography—can be translated into foot-candles. Or you can get a meter that registers foot-candles. For advice, consult your camera dealer, or check with your local power-and-light company. Here in Redding we find the Connecticut Power and Light Company vitally interested in artificial-light plant propagation.
Again “in general,” house plants that require “full sun” when grown in a window need 1200 to 1500 foot-candles of artificial light, and for fourteen hours a day. Foliage plants will get by with 500 to 600 foot-candles. At about 1000 to 1200 foot-candles many plants, and I’m thinking of begonias and gesneriads in particular, will be robust and floriferous.
Should you find it difficult to figure light intensity as suggested above, you might follow the formula worked out by an old friend on Long Island, Elaine Cherry (Mrs. Norman Cherry, the wife of one of our engineering friends). Her formula is easy to follow. “A single forty-watt tube will serve a space approximately four feet long by six inches wide.” Small plants that need intense light can be set up close to the tubes.
Here is a tip—ever notice how your television picture is dim but brightens appreciably when you take a dust rag to the surface of the glass? The same is true of your light fixtures. Wipe them off now and then. Clean tubes give more light than dusty ones, and new tubes give more light than old ones. When a tube darkens at the ends, that means it has seen better days and should be replaced. According to Mrs. Cherry, it is a good policy to replace tubes after five thousand hours of service and not wait for the dwindling light to curtail the rays your plants need. While you are at it, it’s smart to insert new starters.
TYPES OF TUBES
Until the introduction of the Gro-Lux lamps, we had to choose types designed primarily for illumination. And there were as many choices and combinations as there were tube types. In a private and somewhat limited survey, I’ve found that when only one type of tube was used, cool white was to be preferred. In combinations of equal or two-to-one proportions, some growers use daylight and natural tubes; others prefer daylight and de-luxe warm white. And there are those who go for cool white and de-luxe warm white. Those who supplement their lights with 10 per cent incandescent light seem to favor all daylight fluorescent tubes.
The object of all these different combinations is to get the most favorable balance of red and blue rays. If you are a hobbyist who grows plants for the love of them, and not necessarily for their value in interior decoration, the new Gro-Lux tubes are less complex and less troublesome. You don’t have to be a light expert to get results and have fun with your light-garden.
CARE OF PLANTS
Temperature, humidity, soil, fertilizing, potting—almost without exception, plants growing under artificial light need the same care as window-garden plants. But since the light is an artificial substitute for natural sun and light, watch for signs that the plants are not entirely satisfied with it. When they stretch out, get long and lanky, or the foliage has a weak, wan color, set the plant up closer to the tubes, or over toward the center where the light is strongest. You might do well to make room by shifting some of the plants that have been in the center. Sometimes when a plant has too much light it will become stunted. Until a more exact rule book is written, you will have to use your own good common sense.