In nature, where plants grow without cultivation, there is always a mixture of plant types growing in an area. The selection of the plants living in an area depends on the soil type, local climatic conditions and horticultural history. With a few exceptions, the plants that grow together in the wild are mutually beneficial, in that they allow for maximum utilization of the light, moisture and soil. Plants needing less light live in the shade of those which must have full light, while the roots of some plants live close to the surface, and others send their roots far down into the subsoil. Some plants will hurry into bloom and flower early in the year before their neighbors have yet to produce leaves, which will cut off the light supply later in the year. This is known as companion planting when it is practiced in the garden. Companion planting enables the gardener to maximize use of sun, soil and moisture to grow mixed crops in one area.

In planting a vegetable garden, you should use plants that are mutually compatible and make demands on the environment at different times. Vegetables may be divided into heavy feeders, light feeders, soil-conserving and soil-improving crops. The heavy feeders should be planted in soil that has been newly fertilized. Among the heavy-feeding vegetables are cabbage, cauliflower, all leaf vegetables such as chard, head lettuce, endive, spinach, and celery, celeriac, leeks, cucumbers, squash, sweet corn, and tomatoes.

The heavy-feeding vegetables should be followed by such light feeders as pole beans, bush beans and other legumes. Light-feeding vegetables are great lovers of compost. Also, better than other kinds of plants, they seem to use the finely pulverized raw rocks and make phosphorus, potassium and many trace elements available to other plants.

Other light-feeders are such root crops as carrots, beets, radishes, turnips, and rutabagas. Most herbs are light-feeders.

Some plants have a beneficial effect upon the garden by virtue of some peculiar character of their growth, their scent or their root formation and soil demands. Among these plants are sunflower, hemp, blossoming hyssop, thyme, savory, borage, and other good bee-pasture plants. Odoriferous plants, including those with aromatic oils, play an important part in determining just which insects visit the garden. Hemp, for instance, is said to repel the cabbage butterfly.

However, there is more to companion planting than just arranging the physical needs of plants for optimum use of your garden space. Although the hard scientific evidence is often lacking, there is a whole host of insect repellent properties attributed to different combinations of plants. In addition, there are combinations of plants that seem to be natural enemies. When planted too close together, the result is often depressed yields of one or both plants. In most cases, plant scientists still do not know all the why's of these relationships. Many theorize that it is root exudates, or leaf secretions. The odor of one plant may be desirable to an insect, but the odor of a neighboring plant may overpower the attractive scent and send the insect packing.

The listing of companion plants and antagonist plants presented here is based on scientific evidence as well as on folklore. What is reported as working in one garden may not work in yours. Then too, you may hit on a beneficial pairing not yet reported. The main thing is not to plant your garden in strict mono-cropped rows. Diversity of plants is the easiest and most effective pesticide and fertilizer the garden has, so use it liberally!