Yard Crops That Complement Each Other : Gardens: In small spaces, companion planting offers efficiency. Shading, support and windbreaks are among the advantages.

Companion planting, as its name indicates, is a friendly, old-time garden practice. It means growing two or more different kinds of plants close together with the hope that some mutual benefits will result.

Early settlers in America found Indians planting corn and pumpkins close together.

In small, space-limited gardens, companion planting offers efficiency. It’s not the same as successive planting, which refers to garden arrangements in which an early maturing crop is followed by a late-maturing crop as soon as the first has been harvested.

In short, companion planting uses several plantings at the same time. For example, radishes, spring onions or leaf lettuce can be planted so that rows of sweet corn, peppers or tomatoes can be sown between them. The early crops mature before the taller crops shade them too much. Also, as shading begins, vegetables such as leaf lettuce are kept cooler and produce longer.

One plant may also form support for another. A common example is close planting of climbing green beans and tall varieties of sweet corn. Tall plants may also become windbreaks for tender, smaller plants growing nearby.

Roots of some green plants develop a symbiotic relationship with beneficial fungi in the soil called micorrhiza. They may produce growth substances or help the uptake of such nutrients as phosphorous. Crops growing close together may share the same micorrhiza, which improves growth and, it is thought, may seem to indicate that the plants “like” each other.

There is some controversy about beliefs that some plants can protect other plants against attack by some insects.

A few years ago, companion trial tests took place at Pennsylvania State University to determine whether radish protected against striped cucumber beetle; marigold against Mexican bean beetles; thyme against cabbage worms; onion against leaf hoppers on carrots, and catnip against flea beetles on eggplant.

The results showed that none of these plants could protect its companion from attack by any pest.

Another concept--that marigolds protect nearby plants from nematodes--found no verification in University of Georgia test. A study showed that some marigolds attracted nematodes that are then killed within the roots. A researcher reported that this concept would be useful only to suppress the buildup of nematodes but would not protect existing plants from them.

Companion planting can make the garden more attractive. Close spacing can also keep weeds down as plants mature, and some plants attract bees, which can help in the pollination of other plants nearby.