Wednesday, December 22, 2010

Companion Plants --- Practical Gardening Advice or More Confusion?

"Planting polycultures (using multiple crops in the same space) to prevent insects from becoming established is on of the best means of providing protection to your garden there is." (Source: The Truth about Organic Gardening, by Jeff Gillman, pg74).  Dr. Gillman also states "Don't plant the same types of plants next to each other.  When you do you offer insects the opportunity to eat their fill of one plant and then simply move on the one next to it." 

"Most people think of plants as very passive organisms. They grow almost unperceptively, and only once a year do they flower or produce edible products. However, plants are very active in ways that are not so obvious to the casual observer. For example, plants change the chemistry of the soil, and influence the types of microorganisms that grow there. They actively compete with other plants for space. Some will poison their neighbor's offspring to maintain a competitive advantage, while others change the environment in ways that benefit other species. Plants wage a constant battle with insects, relying heavily on chemical warfare."  (Source:

Many land grant universities will state there has not been sufficient research done to substantiate the value of companion plants in the garden.  After all, that plant is supposed to protect your valued vegetable plant by either repelling harmful insects, inviting beneficial insects, or exude chemicals into the surrounding soil that may harm or deter unwanted insects and other pests.    Some will provide a list for your use with a disclaimer such as this one at Cornell University:   Adding these plants to the soil will increase competition for the valuable resources our vegetables need --- light, water, nutrients, and space.  

Dr. Linda Chalker-Scott ( states: "There is no scientific basis, however, for any of the several lists that exist describing “traditional companion plants”. Like horoscopes, these lists may be fun to use, but they should not be perceived or promoted as scientifically valid any more than astrology. Furthermore, those of us who value the science behind our horticultural practices should avoid using this phrase for precisely the same reason."  

"The magic and mystery of companion planting have intrigued and fascinated humans for centuries, yet it is a part of the gardening world that has never been fully explored."  (Source:  Carrots Love Tomatoes, by Louise Riotte, pg 1).  Gardeners have recommended certain combination of plants for a long time.  None has been scientifically proven to perform as these gardeners claim, but some do seem to make good common sense as interplants. Test them yourself.  Let's share what you have learned. 

I find that too often, the plant lists are incompatible with considering Central Florida gardening seasons.  For example, rarely do we plant tomatoes and carrots together.  Tomatoes are warm season crops and carrots are cool season crops.  I believe that some benefits could be derived by some "intercropping" of vegetables such as the Three Sisters garden suggests: corn, beans and squash (  For the so called "companion plants" that can be used as a trap crops to lure certain pests from the vegetable garden, I like to keep them in containers so I can move them about in the garden and keep them from competing with my valued vegetables for the limited resources in the garden --- light, water, nutrients and space.  

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