Getting To Know Companion Plants

Leslie Fitzwater, KC Master Gardener 2002

I first became interested in companion plants several years ago when a television gardening show host suggested planting basil among tomato plants to enhance the flavor of the tomatoes.  The concept made sense to me; after all, basil is a widely-used ingredient in many tomato-based dishes.  This herb and fruit combine together deliciously in the kitchen, who’s to say they can’t also complement each other in the garden? With the growing season several months ahead of me, I decided to study this concept of companion plants to see what other combinations I could find.

My first stop was at my local branch of the Kanawha County Public Library where I found multiple references to companion plants and at least two volumes devoted solely to the topic.  Author Louise Riotte has written two books specifically about companion plants, “Roses love garlic: companion planting and other secrets of flowers,” and “Carrots love tomatoes: secrets of companion planting for successful gardening,” both of which are available through the library system and at local bookstores.  Both volumes are a good start for those interested in learning more about companion plants.  Another good source of information on companion plants is the Internet.  A search of www.google.com turned up more than 1 million results for the term “companion plants.”

As I continued to research this topic, I learned that companion planting is not a precise science.  What some authors consider to be companion plants, other authors do not.  The pairings and combinations I discuss in this article are ones I have found to be widely accepted by multiple sources.  Although everyone may not agree on which plants make the best groupings, what every author I read does agree on is that companion planting does work.

The objectives of companion planting are simple:  determine which plants are beneficial to one another; group them together in the garden; and allow them to form symbiotic relationships that result in the plants reaching their fullest growing potentials.  Although using companion plants in the garden is an imperfect science, it is a practice used extensively by gardeners interested in reaping multiple benefits.  Plants that require shade may be planted with taller plants that need sun.  Plants with shallow root systems can be planted alongside those that have deeper roots.  Plants that release nitrogen into the soil can be planted with ones that require large doses of it.  Plants that repel the pests of another plant can take the place of pesticides and other control methods.

Companion plants may be grouped together to achieve multiple benefits as seen in the Native American “Three Sisters’ Garden.”  The practice of growing corn, beans, and squash together is a perfect example of companion planting.  The corn stalks grow tall lending physical support to the beans, which in turn fix nitrogen in the soil enhancing the soil’s growing potential.  The shade of the large leaves of the squash plant help keep weeds from sprouting, and the squash plant itself helps retain moisture in the soil.  This use of companion plants is also referred to as  inter-planting or inter-cropping.

Gardeners often use companion plants for insect, pest, and disease control. Garlic is often planted among roses to deter mildew and black spot.  Roses also get a helping hand from geraniums that, when planted nearby, are thought to ward off Japanese beetles.  Members of the onion family, including shallots, leeks, and chives, allegedly repel moles and mites from garden areas.  On the other hand, companion plants can also be chosen for their abilities to attract valuable insects, such as bees.  Flowers and herbs, like thyme and rosemary, are enticing to bees, luring the bees to the plants and thus increasing pollination.

Flavor enhancement is another benefit gardeners may wish to achieve with companion planting.  When certain plants are grown together they are thought to enhance each others’ growth resulting in more flavorful harvests. As I mentioned earlier, the practice of planting tomatoes and basil is commonly accepted, and the pairing is thought to enrich the flavors of the fruits.  Garlic is reported to increase the production of oils in herbs, and is often placed in herb gardens for this reason. 

Lists of companion plants are available in gardening books and from Internet web sites, and are as extensive as gardeners’ interests.  Vegetables, herbs, flowers, and fruit trees - all have or are companions to lend support and enrichment to each other’s lives.  When planning your next gardening experiment, take some time getting to know companion plants, it could be a relationship that will last a lifetime.