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The effects of light reflection and artificial light on plant growth the urban gardener
Tomato harvests can be improved dramatically in size and quality by growing the plants over red mulch, scientists at the Agricultural Research Service have found. Potatoes and green peppers, by contrast, do best with white mulch. The finding is significant not only for obvious commercial reasons but because it raises new questions about how plant leaves respond to various colors of light. It is well known that different colors of light affect plant growth differently. While green leaves do well in almost any color of light, for example, many plants do not bloom well if deprived of certain parts of the spectrum. The mulch studies show plant growth can be affected not only by the light falling on the upper surfaces of leaves but by the light reflected from below up to the leaves' lower surfaces. The color of this light depends on the color of the reflecting surface on the ground. In most commercial and many home gardens, the surface is mulch, which is any material spread over the soil. The purpose is usually to stop weeds and slow the evaporation of soil moisture. Straw and plastic sheeting, usually black or white, are the most common vegetable mulches. Any colored surface absorbs all colors (turning the light into heat) except those it reflects. Thus, a red mulch reflects only the red portion of the full spectrum falling on it. Tomatoes are often grown over black plastic, which reflects almost no light. Michael J. Kasperbauer and Patrick G. Hunt, who did the mulch studies at the Agricultural Research Service's research center in Artificial light and plant growth
Plants need light to grow, and the chances are good that in a basement apartment there is too little natural light for plants to survive. Many indoor gardeners use artificial lighting to start seeds, grow houseplants and even produce some crops that can be eaten. Fluorescent lights work best. Incandescent bulbs get too hot and will toast any plant that is close enough to benefit from the light. Home centers sell shop light fixtures that hold two 48-inch fluorescent tubes. Plants that don't require much light can be grown under two tubes. Double up the fixtures for plants that need more light. Special plant lights are not required in most cases. Use a cheap tube that supplies bluish light (cool white) in combination with a slightly higher-priced tube that supplies yellowish light (warm white). These will provide a spectrum that will do for many plants. Replace the tubes every year or so. They won't burn out, but the light intensity drops off with time. The fixtures should plug into a timer that turns the lights on and off automatically. Ten to 12 hours of light a day works well. Be sure everything is properly wired and grounded and that you're not overloading the electrical circuit. The distance from the lights is important because light intensity drops off quickly the farther away the plants are from the tubes. Generally the height of the fixture is raised as the plants grow. There are various ways of suspending the fixtures so the height is adjustable. Plans for a low-cost frame for the lights. Many plants do well in soilless potting mix, which is well drained, relatively clean and pest-free. Containers come in all materials, shapes and sizes. They must be a little larger than the root ball and have holes for drainage. It helps if the container is wider at the top than at the bottom, so you can get the plant out when it needs repotting. What would you like to grow? Plants that flower are more challenging than foliage plants. Garden centers get regular shipments of inexpensive, small-size tropical foliage plants that are a good start. The pot labels are generally inadequate. Figure out the Latin name of the plant and learn its requirements by checking a reference book at the library or doing an Internet search. Light, water, temperature and fertilizer are the variables. |
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