What are companion plants?
Companion plants are those who are planted together to help each other. Some of their roles are:
- good friends – help each other grow better
- interplanting – grow together but take up separate spaces or horizons
- nurse plants (provides shade for seedlings)
- repel pests
- attract pollinators
- trap pests (trap plants)
- accumulate nutrients
- condition the soil
SOME PLANTS ARE GOOD FRIENDS – OTHERS ARE FOES
Friends and Foes
- Friends: alliums, beets, borage, buckwheat, calendula, carrots, chamomile, dill, mint, nasturtiums, rosemary
- Foes: mustard, peppers, strawberries, tomatoes
- Friends: beets, brassicas (e.g., cauliflower), carrots, corn, cucumbers, eggplant, peas, potatoes, radishes, squash, strawberries, tomatoes
- Foes: alliums (garlic, onion), fennel, peppers, sunflowers
- Friends: root crops, celery, lettuce, radish
- Foes: None
- Friends: beans, leeks, lettuce, onions, peas, potatoes, radishes, rosemary, sage, tomatoes
- Foes: dill
Cabbage (kale, cauliflower, collards):
- Friends: beans, celery, cucumbers, dill, lettuce, onions, potatoes, sage, spinach, thyme
- Foes: strawberries, tomatoes
- Friends: beans, cucumbers, melons, peas, potato, pumpkin, squash, sunflowers*
- Foes: None
- Friends: beans, cabbage, cauliflower, corn, lettuce, peas, radishes, sunflower*
- Foes: melons, potatoes
- Friends: beans, lettuce, okra, peppers, potatoes, spinach, tomatoes
- Foes: None
- Friends: fruit trees, roses, tomatoes
- Foes: beans, cabbages, peas, strawberries
- Friends: buckwheat, cabbage, nasturtiums
- Foes: pole beans, strawberries
- Friends: beans, carrots, radishes, strawberries, kohlrabi
- Foes: cabbage, celery, parsley
- Friends: cucumbers, eggplant, sweet peppers
- Foes: None
- Friends: beets, broccoli, cabbage, carrots, lettuce, parsnips, peppers, potatoes, spinach, tomatoes
- Foes: beans, peas
- Friends: beans, carrots, corn, cucumbers, potatoes, radishes, turnips
- Foes: alliums (onion, garlic)
- Friends: basil, carrots, eggplant, okra, onion, parsley, spinach, tomatoes
- Foes: beans, fennel, kohlrabi
- Friends: basil, beans, beets, brassicas, corn, eggplant, horseradish, nasturtiums, peas, squash
- Foes: apples, celery, cherries, cucumbers, pumpkins, raspberries, sunflowers*, tomatoes
- Friends: basil, carrots, cucumbers, eggplant, lettuce, melons, onions, nasturtiums, peas, root crops, spinach, squash, tomatoes
- Foes: beans, kohlrabi, potato
- Friends: asparagus, basil, beans, borage, carrots, celery, dill, lettuce, melons, nasturtiums, onions, parsley, peppers, radishes, spinach, thyme
- Foes: beets, brassicas, corn, kale, peas, potatoes
Zucchini and Summer Squash:
- Friends: corn, beans, nasturtiums, marigolds, onions, radishes, melons, mint
- Foes: Irish potatoes
“Model Citizen Plants:” (They get along with everyone)
*Sunflower also applies to Jerusalem Artichokes (sunchokes)
Examples of combinations:
Beans – Fixes Nitrogen
Brassicas or Eggplant – space filler late
Radishes – space filler early
Squash – living mulch
Corn – first planted, serves as trellis for beans
Beans – climb up the corn stalks, fix nitrogen in soil for the corn
Squash or Melon – serves as living mulch, covering ground to keep weeds down, and also serves to deter raccoons, who like corn (the prickles on the stems and leaves don’t feel good on paws)
Sunflower – attracts bees and pollinators, and serves as a windbreak
■Beans – protects the potatoes and eggplant from Colorado potato beetle
■Potatoes – protects the beans from Mexican bean beetle
■Eggplant – protects the beans from Mexican bean beetle
■Carrot – root exudate beneficial to peas
■Sage – repels carrot fly
■Peas – fixes nitrogen in soil
■Tomato – serves as nurse plant to carrots, shading them while they get established
■Borage – protects tomato from tomato hornworm
■Basil – protects tomato from tomato hornworm
■Marigold – root exudate prevents root knot nematode
■Carrots – shaded by tomatoes for early start to season
Different plants use Two (or more) Horizons: Allows dense planting while avoiding competition for nutrients and sunlight. One plant uses more space above ground, another uses more space underground.
Bok choi and turnips (one uses soil horizon while the other is leafy)
Carrots, lettuce, onions – each provides some shade to the others, and uses a different soil horizon.
Brussels sprouts, parsley, spinach, onions – spinach and onions ready before sprouts mature
Three Sisters – corn, beans, squash – and a fourth: sunflower
One plant can shade a seedling until it is strong enough – or the weather is cool enough – for it to grow. Some plants like less sun, so a plant that is taller is planted to provide shade for another.
Carrots and tomatoes (tomatoes shade the carrots planted in late summer; when tomatoes die back, the weather is cool enough for carrots to grow)
Okra and peppers – the okra grows rapidly and taller, and provides a bit of shade to prevent the peppers from being sunburnt by the hot sun of midday summer
Radish, lettuce, peppers – the radish grows faster; lettuce likes the shade of peppers
Some plants help others by repelling pests.
- Borage, when planted with tomatoes, repels tomato worms
- Basil planted near tomatoes and peppers guards against tomato worms
- French and African marigolds deter aphids – contain natural pyrethrines…. …..also helps prevent root knot nematode in tomatoes
- Nasturtiums and Tansy, when planted with squash, helps deter squash bugs
POLLINATOR and BENEFICIAL INSECT ATTRACTANTS
Some plants attract pollinators to help other plants. NOTE: Approximately 90% of garden bugs are pollinators or pest predators and only about 10% are likely to damage crops.
- Pot marigold, calendula – bees and pollinators are attracted
- Nasturtium – attracts bees.
- Clovers: red – attracts pollinators
- Germander (herb) is a strong attractant for bees
- Attract beneficial insects that prey on the pests
- Aster family (artichokes, chicory, dandelion, endive, lettuce, sunflowers)
- Mustard family (arugula, broccoli, cauliflower, collards, kale, mustard, radish, turnips)
- Carrot/parsley family (celery, cilantro, dill, fennel, parsnip)
These plants are more attractive to the pests than the crop you are trying to protect. So plant something for the pests and they will leave your good plants alone!
- Sunflower is a trap plant for grasshoppers
- Amaranth is a trap plant for cucumber beetles
- Sorghum is a trap plant for aphids
- Nasturtium is a magnet for caterpillars
NUTRIENT ACCUMULATORS AND SOIL CONDITIONERS
Some plants are good for gathering nutrients to make them available for other plants. They are called “Dynamic Accumulators”. Other plants help condition the soil by either having long roots to make channels for water to flow down or earthworms to crawl up. They also encourage beneficial micro-organisms in the soil.
- CLOVER: white – green manure for fixing nitrogen as well as phosphorus
- Borage makes available silicon and potassium
- Dandelion captures sodium, silicon, magnesium, calcium, potassium, phosphorus, iron and copper
- Lamb’s quarters capture nitrogen, calcium, potassium, phosphorus, manganese
- Marigolds capture phosphorus
- Comfrey is good for silicon, nitrogen, calcium, potassium, iron, magnesium
- Gayfeather, a native prairie flower, has roots nearly 16 feet long!
- Daikon radish roots break up soil.
- Dandelion roots are often long and break up soil.
RESOURCES FOR FURTHER READING
Christopher Shein, The Vegetable Gardener’s Guide to Permaculture: Creating an edible ecosystem, Timber Press, Portland, OR, 2013.
Jay L. McCaman, Weeds and Why They Grow, Jay L. McCaman, Sand Lake, MI, 1994.
Louise Riotte, Carrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening, Garden Way Publishing, Charlotte, VT, 1978.
Daron Joffe, Citizen Farmers: The Biodynamic Way to Grow Healthy Food, Build Thriving Communities, and Give Back to the Earth. New York: Stewart, Tabori & Chang, 2014.