Companion planting is planting two plants together so that both grow better. In some cases, the second plant is bait for the pests that would otherwise plague the first, more desirable, plant. Before chemical pesticides were available, companion planting was used as a method of pest control, to provide nitrogen for plants that needed more than the soil could give, and improve the harvest of food plants.
In addition to repelling pests, companion planting can attract beneficial insects. Planting flowers that bees and hummingbirds are attracted to can improve the pollination rates for your vegetables. Companion plantings also take into account plants that do not get along well, such as dill and fennel, or that cross pollinate, such as cucumbers and cantaloupes.
I should mention that much of this information is based on folklore, not scientific research. Scientists are only now beginning to seriously research the issue so peer reviewed studies are hard to come by. However, there are records of companion planting in the writing of Theophrastus (300 B.C.E.), Pliny (50 C.E.), and John Gerard (1597 C.E.). Something that endures for that long is likely to be of some validity.
The most famous companion planting practice in North America is the planting of corn, pole beans, and squash by Native Americans. Not only did the corn stalks provide support for the pole beans, the corn shaded the squash from the hottest part of the sun. The beans fixed nitrogen and returned it to the soil where the corn could use it. All the plants benefited and grew better when planted together.
Another classic combination is planting marigolds around your tomatoes to deter nemotodes. I have done this and noticed significantly fewer problems on my tomatoes than when I do not plant the marigolds. The bright yellow flowers look nice, too.
Companion planting can be very complicated with endless combinations of plants. I do not have room to go into that here. However, there is a classic book called Carrots Love Tomatoes by Louise Riotte that discusses the ins and outs of companion planting. I have included an affiliate link to the book below.
What combination of plants have you used in your garden? How have they helped or harmed your harvest?
For more help gardening, buy my book, Preparing A Vegetable Garden From The Ground Up
Available in print or ebook from Amazon.com or other retailers, this book walks you from choosing the site of your garden all the way through what to do after the harvest. Buy a copy for yourself or a friend today!