Companion Planting Guide

What is Companion Planting?

Companion planting, or companion gardening, has been around a long time. Gardeners throughout agricultural history have known that it works to improve the vigor of their plants. Only recently, however, have scientists understood why it works.

History of Companion Planting

Even before agriculture was created around 12,000 years ago, nature evolved companion vegetables and fruits. Beans, squash, and teosinte (the progenitor of maize or corn) grew together in the wild in Mexico. As people settled down and they copied what they saw in the wild with garden companion planting.

Growing beans, corn, and squash together spread throughout the Americas, with the Iroquois people eventually naming it the “Three Sisters.” The “Sister Plants” are still grow today as part of vegetable garden companion planting.

Fast forward to the 20^th Century, Richard B. Gregg published a pamphlet in 1943 titled “Companion Plants and How to Use Them.” While he didn’t invent the idea, he did become a pioneer in the field of modern companion planting. Twenty years later, his book of the same title was released. The book contained his experiments with companion cropping along with the laboratory experiments of Dr. Ehrenfried Pfeiffer.

With the rise of organic gardening in the 1970s and 80s, companion planting had another surge in popularity. Vegetable companion planting was the rage in many gardens. Louise Riotte added to the trend with her books, Carrots Love Tomatoes (1975) and Roses Love Garlic (1983). She wrote about what plants grow well together –vegetables in the first book and flowers in the second—and what plants don’t grow well together. A whole new generation was introduced to compatible vegetable gardens.

A lot was going on in the 1970s organic gardening movement. Bill Mollison and David Holmgren coined the term “permaculture.” At the basic level, permaculture is a design system based on ecological principles. The Three Sisters and companion planting fell nicely under the permaculture umbrella.

Today there are two camps on whether companion planting works. There are those that think compatible vegetables benefit each other and those who think companion planting is a farce. Certainly a shade loving plant benefits from growing under a sun loving plant. And the nitrogen fixing bacteria in the nodules of legume (bean) roots benefits many plants that can’t make usable nitrogen. But, the idea of plants “liking” each other in some magical way, as espoused by Riotte in her books, can’t be proved. (Those books still have a lot of other great information!).

Benefits of Companion Growing

The idea behind companion planting is that plants can benefit from being planted near other plants of a different species. These plants can help each other out by providing nutrients in the soil, attracting beneficial insects, protecting each other from wind or other elements of the weather or by acting as a decoy for harmful insects. Companions also help make your garden more efficient: vining plants can grow beneath upright plants and share space.

Companion planting is an important component in Integrated Pest Management and can be great tool for the organic gardener or farmer. Companion planting is about creating plant communities rather than monocultures. These communities are healthier and more resilient than their one-plant counterparts. By bringing balance to the garden landscape, nature can do its job in growing nutritious, delicious fruits and vegetables.

Trap Cropping

Sometimes someone needs to be sacrificed for the greater good of the garden. A decoy plant can be grown near desired plants to lure insects away from the main crop. For example, collards draw the diamond back moth away from cabbage.           

Fixing Nitrogen

Peas, beans and clovers are part of what is collectively known as the legumes. These helpful plants can take nitrogen from the air and “fix” it, or make it available to other plants without this fixing ability. Technically, it is the bacteria on the rhizomes of the legumes that do the fixing, but the legumes get the credit.

Suppressing Pests

Some beneficial plants can repel or suppress pests by excreting chemicals from their roots or vegetation. This not only benefits the exuding plants, but any other plants that are growing around them.

 Physical Interactions

Don’t think this refers to hugging (although some plants might like that), physical spatial interaction can yield pest control benefits and increase yield. Tall-growing plants that love to be in full sun can shade lower-growing shade-preferring species. Prickly vines grown on sweet corn may prevent raccoons from stealing your crop. These plants help each other out by their mere presence.

 Nurse Cropping

Behaving in a similar way to physical interactions, nurse crops can protect more defenseless plants by shading or cutting the wind. Oats have been used for a long time to help alfalfa get established. The oats out-compete with weeds that could impede the alfalfa’s growth.

 Beneficial Habitats

Some plants provide beneficial habitats (also known as refugia) for parasitic and predatory insects. When these critters have a home in your garden, they can go forth and munch on harmful insects.

Diversity Security

Growing a wide diversity of plant species, or even cultivars, can ensure that if one crop takes a beating from pests or disease, there are still lots of others left to provide food or pretty garden views.

Companion Planting How-To

Put away the synthetic fertilizers, herbicides and insecticides. After incorporating companion planting into your organic gardening routine (along with building healthy soil, composting, mulching etc) you won’t need them. Your plants will be better off and so will the environment.

Before you decide what vegetables to plant together (or herbs or flowers) check with local experts (Master Gardeners, Cooperative Extension Service, Native Plant Societies, local garden shops etc.) to find out what plants grow best in your area and what harmful insects or diseases you should be on the lookout for.

Keep track of which plant partners work well together. Your garden is different than anyone else’s, so it is important to keep good notes and experiment with different companions from year to year until you find the best recipe for your own success.

Companion Planting Garden Layout

To create a companion garden layout, you can use a companion planting chart. A companion vegetable planting guide can get you started with what vegetables to grow together. These are some of my favorite books on companion gardening.

However, you might not want to grow everything in these books. Or perhaps you can’t easily grow certain plants in your area. (I live in Montana, believe me, I am familiar with this.) I recommend choosing what you want to grow and then seeing if there are any companion plants that will work with them. Keep track over the seasons and write down what seems to be working and what doesn’t.

Tomato Companion Plants

Marigolds emit a strong odor that repels black flies and greenflies; intersperse them with your tomatoes to keep the fruits fly-free. Add some asparagus and it will help keep nematodes from attacking the tomato’s roots. Basil also helps out tomatoes by improving their growth and flavor. Basil repels thrips, flies and mosquitoes. And then you are two-thirds of the way to a Caprese salad.

Onion Companion Plants

The onion-y scent of chives can repel aphids from chrysanthemums, sunflowers and tomatoes. Onions are also known to repel cabbage loopers, cabbage worms, and cabbage maggots, so they are great to plant with plants in the cabbage family: broccoli, kale, Brussels sprouts, and cabbage.

Cabbage Companion Plants and Dill Companion Plants

Cabbage is helped out by its proximity to tomatoes. The tomatoes repel diamondback moth larvae that chew holes in cabbage leaves. Plant dill along with members of the cabbage family (broccoli, Brussels sprouts and, of course, cabbage). The cabbage lends support to dill and dill draws in beneficial wasps, which prey on cabbageworm and other cabbage pests.

Sage Companion Plants

Plant sage with members of the cabbage family or carrots to keep pests away.

Carrot Companion Plants

Plant leeks and carrots in the same vegetable patch since leeks keep carrot fly away and the carrots will repel leek moth and onion fly.

Lettuce Companion Plants

Chervil will keep aphids off your lettuce. Growing tall flowers in the lettuce will provide shade in the heat of summer.

Garlic Companion Plants

Garlic also wards off aphids and works particularly well when planted with roses, as does garlic chives. Plus, the purple chive flowers look nice with roses.

Cucumber Companion Plants, Nasturtium Companion Plants, and Squash Companion Plants

Let your cucumbers and squashes intertwine their vines with nasturtium. The pretty orange-flowered plant will repel cucumber beetles and provide habitat for predatory insects such as spiders and ground beetles.

Corn Companion Plants and Bean Companion Plants

Corn and beans can be great friends as beans attract leafhoppers, fall armyworms, and leaf beetles (all beneficial insects that prey on corn). The corn literally holds up the bean vines. Companion planting beans also adds nitrogen to the soil since bacteria in legume roots can make atmospheric nitrogen available to plants. If you boast very fertile garden soil, you can grow purslane as a ground cover in the corn patch. Then cook it up in a stir-fry.

Radish Companion Plants

When radishes are grown near spinach, they draw leafminers away from Popeye’s favorite food. The damage done to the radish leaves doesn’t affect the underground growth.

Companion Planting Flowers

Marigold companion plants are probably the most well-known companion flowers for vegetables. Marigolds and tomatoes are known to go hand in hand. I mentioned marigolds and tomato plants in the best companion plants for tomatoes section above. Marigolds in the vegetable garden add color and scent (though today’s marigolds are nowhere near as strong-scented as they used to be). Planting marigolds with tomatoes can repel some flies, thirps, and hornworms. If you are wondering where to plant marigolds in the vegetable garden, plant them 18-24 inches from the tomato plant seedling.

Sweet alyssum smells nice and its little flowers attract beneficial insects. Plant it next to bushy crops like potatoes or underneath arching plants like broccoli.

The sweet nectar of dwarf zinnias lures ladybugs and other predators away from cauliflower. Zinnia also attracts hummingbirds that eat whiteflies.

Geraniums look good, smell good and repel cabbageworms and Japanese beetles, so plant them around grapes, corn, roses and cabbage.

Companion Planting Herbs

Grow summer savory along with onions and beans to improve their flavor. The savory will attract honeybees and repel black aphids, cabbage moths and Mexican bean beetle.

Other Good Companions

Below are plants that can be mixed in wherever they are needed.

Coriander is one of the great companion herbs. It can be helpful in warding off aphids, while dill attracts beneficial insects such as hoverflies and predatory wasps that eat aphids. Anise does the same thing and grows well with coriander.

The strong scent of tansy keeps ants at bay.

Grow legumes (peas, sweet peas, beans, lupines) in different places each year. They fix nitrogen from the air and make it available to other plants. They are good companions to carrots, celery, chard, corn, cucumbers, eggplant, potatoes, brassicas, beets, radishes and strawberries. Legumes are especially good company for corn and grain, which are heavy nitrogen users.

Yarrow is known to boost the vigor in other plants while at the same time taking up calcium, silica and phosphorous. Add this mineral-rich plant to your compost to boost its nutritional value. Yarrow also attracts beneficial critters such as ladybirds and hoverflies.

Alfalfa is a plant that is resistant to almost all diseases and insect pests. Plant it throughout the garden during the off-season (as a cover crop) and it will improve the soil by fixing nitrogen, accumulating iron, potassium, phosphorous and magnesium. Plow it under in the spring to give the soil—and the plants that grow in it—a nutritional boost.

Borage is a good companion to most plants. It repels cabbageworms and tomato hornworms while attracting beneficial bees and wasps. Borage also increases resistance to insects and diseases for any plant growing near it. Plus, the flowers are edible.

Yummy-smelling lavender repels moths, whiteflies and fleas while providing food for butterflies and other beneficial insects. Lavender companion plants can be used to make a tincture to help with headaches or dried and put into a sachet to help you relax or sleep.

Mint repels a whole slew of harmful creatures: ants, white cabbage moths, fleas, rodents, flea beetles, and aphids. It attracts earthworms, predatory wasps and hoverflies. Be cautious with mint, as it is very invasive.

To repel asparagus beetles, certain aphids, tomato worms, leafhoppers, Mexican bean beetles and general garden pests plant petunias.