Happy Together

By Diane Olson

Companion planting in the vegetable garden.
by Diane Olson

NOTE: To check out the companion planting table (which would have been terrible to try to lay out in HTML), download the pdf: CLICK HERE

Plants, like people, have complicated relationships: Some are deep and beneficial, others shallow and of little consequence, and some are downright toxic. Take broccoli: It grows larger and tastier hanging out with onions, potatoes and beans, and healthier under the protection of rosemary, sage, dill and chamomile. It’s OK sharing space with light feeders, such as beets, nasturtium and marigolds, but tomatoes, pole beans and strawberries cramp its style, by siphoning off calcium. In turn, broccoli becomes downright nasty around lettuce, poisoning the seedlings with its burley roots.

The practice of companion planting makes use of the complex interactions among plants. The National Sustainable Agriculture Information Service defines companion planting as: the establishment of two or more plant species in close proximity so that some cultural benefit (pest control, higher yield, etc.) is derived. Basically, it’s organic gardening in its most basic form, as it is simply utilizing the natural abilities of plants. Companion plants can be used for a variety of purposes, including to:

•    Repel insects, plants or other pests, through chemical means

•    Produce odors to deter or confuse pests

•    Draw pests away from crops

•    Hide crops from pests

•    Provide breeding grounds for beneficial insects

•    Provide food for beneficial insects

•    Improve flavor of nearby plants

Companion planting has been used since at least ancient Roman times and probably long before that. (The first evidence of plant domestication is approximately 10,000 years old; the first society primarily dependent on domesticated crops and livestock developed about 6,000 years ago.) One example that pretty much everyone has heard about is the “Three Sisters” technique of interplanting, which originated in North America with the Haudenosaunee, or Iroquois, and has long been used in the Caribbean and throughout the Americas.

In the Three Sisters planting, corn, beans and squash are planted in the same hole, and each benefits the other: The corn provides support for the climbing beans; the beans supply extra nitrogen to the corn and squash; and the squash limits weed growth. The grower benefits, too, from increased crop yield and the efficient use of space.

Flowers are often used in companion planting to protect crops from pests-sometimes in a round-about manner. Nectar and pollen-rich species, such as goldenrod and yarrow, can be used to lure beneficial insects to the garden, and dense, low-growing flowers like alyssum provide both food and shelter. Some flowers-most notably marigolds-exude chemicals from their roots that suppress or repel pests and protect neighboring plants, and others, such as nasturtiums (a favorite of caterpillars), are used as magnets to lure pests away from crops. It’s basically a benign form of chemical warfare, conducted entirely with nature’s own formidable weapons.

Herbs, too, are used as companion plants, both for their not-fully-understood ability to subtly change the flavor of the plants around them, and for their appeal-or lack of-to pests. Basil, the star among herb companions, does triple duty: It improves the flavor of tomatoes and peppers; repels aphids, mites and mosquitoes; and acts as a fungicide. And it’s darn tasty, too.

If it all sounds complicated, well, it is. Fortunately, other people have done the work to find out what to plant, or not plant, with what, so all you need to do is consult the accompanying chart as you plant the late spring/early summer phase of your garden. Keep in mind that you can incorporate companion flowers and herbs into your vegetable garden by using them as a border or backdrop, as well as by interplanting them in the beds.

CLICK HERE to download the handy, printable table of companion planting guidelines.

Diane Olson writes and gardens in Sandy, Utah.

This article was originally published on April 30, 2007.