Companion Planting Does It Work?

The following was taken from K-States weekly horticulture newsletter. Thought it would be of interest to the masses and probably start some discussion! Dennis

Companion planting is a procedure that is sometimes recommended to naturally reduce pest problems by planting two types of plants close to one another. For example, planting catnip with cabbage is supposed to reduce worm damage on the cabbage. Controlled studies are needed to determine whether such a practice is effective. We now have results from two studies that give some insight into companion planting.
The University of California looked at the effect of planting cabbage with catnip, nasturtium, marigold, summer savory and basil. The cabbage-catnip plots had reduced cabbageworm eggs and larvae but the amount of worm injury was the same. Also, the average weight per cabbage head was reduced probably due to competition from the catnip for sunlight, water and nutrients. The other cabbage companion plantings also failed to show positive results.
The University of Georgia studied companion plantings of beans-marigolds, cucumber-nasturtium, cabbage-thyme, eggplant- catnip, tomato-marigold, and tomato-basil. None of these combinations prevented insect damage from the major garden insect pests.