Companion Planting, a Win-Win Proposition

Photo credit Echonet.org blog

 Crabapple LandscapExperts are asked, “What is companion planting?”

Companion planting is the belief that certain plants can benefit target crop plants if planted together in close proximity. Companion planting is a form of “polyculture” and involves planting different types of plants next to each other for mutual benefit. The opposite is a “monoculture” such as a corn field or putting green on the golf course, where only one type of plant is grown in the space.

 Companion plants:

Use garden space efficiently, with two or more plants growing in the same spot	For example,  tomatoes with marigolds
Prevent pest problems by repelling pests	catnip reduces the number of flea beetles on cabbage and collards
Lure pests away from crops because they prefer the sacrificial plants	peppers and ragweed
Help each other grow	vining pole beans growing up tall corn plants
Attract beneficial insects such as predators and pollinators more efficiently than crop plants	zinnia nectar and a cauliflower crop
Provide shade for crop plants	short lettuce with taller cleome or nicotiana

By combining plants the gardener draws on the strengths of each. For example, French Marigolds are often planted with tomatoes, since both enjoy sun and hot weather.  Research has shown that chemicals exuded by the roots of marigolds eliminates certain types of root-knot nematodes that otherwise damage the tomato roots, causing swellings on the roots or causing the roots to form like short clubs, which makes the uptake of water and nutrients impossible.

French marigolds

Although a row of short French marigolds planted beneath tomatoes provides a memorable photo, Crabapple LandscapExperts advise the gardener to plant a solid bed of marigolds first, before planting with tomatoes, in order to drastically reduce the number of soil-borne root-knot nematodes.  

Aother example is planting carrots and onions in order to benefit both crops. The smell of the Allium covers the smell of the carrot foliage, and insects have more difficulty finding them and mostly eliminates carrot fly damage (larvea invade carrot roots).  In exchange, the carrot performs the same service to the onions, acting to confuse the onion fly.

Often a row of roses is under planted with chives, garlic chives or garlic because they are said to repel Japanese beetles and other rose pests. Whenever planting Tulip bulbs, be sure to plant a clove of garlic in the planting hole to repel larger pests (mammals) like chipmunks or pine voles, thereby ensuring that the colorful tulips will come up and flower next spring.  

Chives Blossom 

Strong-smelling herbs and plants that are said to repel pests or otherwise benefit other plants include chives, nasturtiums, mints, pennyroyal, garlic, tansy and French marigolds.  Despite numerous testimonials, however, the University of Georgia Extension says further research is needed to verify many claims of the effects of companion plantings.

Digging Deeper

View the Companion Planting Chart from the Organic Garden Goddess webpage:  

Read more on Organic Gardening's Beginners Guide to Companion Planting.