Companion planting has long been part of the organic gardeners tool kit. We’re all aware that some crops aide in the growth of other crops. The “three sisters” — corn, squash and beans — are probably the best known example of different plants that do well when planted close by. Other plants are known to repel pests. Geraniums are often planted in the garden to repel leafhoppers, corn earworms, even mosquitoes. And planting legumes — beans, field peas, hairy vetch – where heavy feeding vegetables will later grow helps increase soil nitrogen.
One problem with these principles is that there’s little scientific study to back up what we know from experience. And, in the case of companion planting, some of the scientific “proof’ can be questionable (scroll down). But science is beginning to take a serious look at one form of companion planting known as allelopathy. Scientists have discovered that certain plants have the ability to produce toxic substances that inhibit the growth of other plants. And when those “other plants” are common weeds, well, the ears of organic gardeners begin to perk up. (more…)