1. 2217 Washington Street
Greenville, Texas 75401
(903)455-9885
April 3, 2009
TO: Greenville Herald Banner
Tawakoni News
Country World News
Wolfe City Mirror
Commerce Journal
Kuumba Heritage
Celeste Tribune
Lone Oak Newsletter
FROM: Thomas Clark
Master Gardener
Hunt County
SUBJECT: Weekly News Column B On the Grow
Are you a people person? The theory of companion planting is largely the same.
Just as not all children on the playground play well with others, there are plants that bring
out the best in others and plants that inhibit others. This idea is not new. Allelopathy
was described in 1937 by plant physiologist Hans Molisch as inhibitory or stimulatory
biochemical interactions between plants. The history of these concepts goes back to
dates BC. Research this on the Texas Agrilife Extension website if you would like more
information on the history.
Companion planting is a method that may enable you to have better and more
quality yields from your vegetable garden or a better landscape with less effort. This
methodology is part folklore, part research. If you walk in the woods, certain plants
flourish next to each other, but in other areas they may not live. You may be witnessing
a natural example of companion planting. Companion planting is a more general term

2. than allelopathy. Allelopathy focuses more on the chemical relationships and how they
may affect the plant. An example is pine bark and needles on some trees may have
sufficient tannins that over time become concentrated near the tree to the point of
inhibiting nitrogen fixing microorganisms in the soil. This affects the growth of grass
and other nearby plants. Shade is not always the culprit.
Companion planting takes in many general ideas. Recall the three sisters. Native
Americans planted corn, squash, and beans together. Corn uses a lot of nutrients, but
beans, being nitrogen fixing, help restore the soil while the corn gives them a natural
trellis. Squash grows low and shades the soil to help retain moisture and shut out weeds.
Real teamwork! Trap cropping is when a sacrificial plant is placed in with desirable
ones. The idea is that the pests can be attracted by a decoy and killed or removed with it.
Monoculture often brings in more pest load. So breaking up plantings with other crops
can lower the attraction your plantings have for pests. Positive hosting is planting targets
that attract beneficial insects that feed on pests. Pest suppression is planting to repel
critters and pests. Various flowers and plants such as garlic are seen as undesirable by
much of the pest and critter world. The challenge is to compare lists of companion plants
and develop a garden layout that grows compatible plants in a manner to stimulate
growth, taste, and overall quality, while decreasing the downside of pest load and plants
that might compete with each other. For example tomatoes are said to do better next to
carrots and asparagus but potatoes and cabbage may hinder them. You can find all sorts
of sources. Organic Gardening and Farming in 1972 reported that borage could deter
tomato worms and improve growth and flavor. This statement leaves a bit to learn. Try
it but keep records, certain varieties may be affected but not others. As well as the Texas

3. Agrilife Extension, you can also search the National Sustainable Agricultural Information
Service for information on companion planting.
Roses Love Garlic and Carrots Love Tomatoes are two books directly speaking to
companion planting. Many other authors such as John Jeavons in How to Grow More
Vegetables have written on the subject as well.