For Better or Worse - A Guide to Companion Planting

Many experienced gardeners already know that having a diverse mix of plants helps give you a beautiful and healthy garden.   Some also believe that certain plant combinations have extraordinary powers for helping each other grow.   Scientific study of companion planting has confirmed that some combinations have real benefits unique to those combinations, while experience has demonstrated to many gardeners how to combine certain plants for their mutual benefit.
How can companion plantings help you?

• Companion plantings brings variety into the garden by helping to break up the monoculture, this aids in deterring disease and bad bug infestation.
• It’s a holistic approach to working with the intricate layers of the ecology of your garden.
• Reduces the need for fertilizers and pesticides. Many vegetables and herbs store natural substances in their roots, flowers and leaves that repel unwanted pests and attract beneficial insects.
• Enhances the beauty as well as the flavor and overall health of your garden by working in harmony with nature.  

How close should the plants be to each other?

• Take the average spacing between the two varieties.  

Ancient Companions Over the centuries, companion planting has played a vital role in the survival of people throughout history. The Iroquois American Indians in the Northeast used the “Three Sisters” or De-o-ha-ko. De-o-ha-ko literally means “our sustainers” or “those who support us”. When companion plantings are used they help one another grow, thrive and produce higher yields efficiently and with little impact on the environment.  

Scientific Foundations for using Companion Plantings
Trap Cropping – one plant will lure bugs and pests away from another plant and serves to distract.  
Symbiotic nitrogen fixation – legumes (peas, clover, beans) fix atmospheric nitrogen for their own use and benefit of nearby plants via symbiotic relationship with rhizobium bacteria.  
Biochemical pest suppression – certain plants give off chemicals in their roots or aerial parts that suppress or repel pests and protect neighboring plants.  
Physical spatial interactions – tall growing plants which love sun sharing space with low growing shade tolerant plants gives higher yields in less space, as well as yielding pest control.  
Beneficial Habitats – or refugia is when companion plants provide a desirable environment for beneficial insects and other arthropods, like predatory and parasitic insects which help keep the pest population in balance. Agroecologists believe this is a good way to both reduce pest damage and pesticide use.  
Security via Diversity – a mixed variety of plants, herbs and vegetables helps limit the possible destruction that can be caused to a single crop or cultivar. Simply mixing cultivars will achieve the diversity needed as the University of California demonstrated with broccoli.
As much as there are plants that are compatible together, there are some that are just as incompatible together as well.  Please refer to our Companion Planting Guide that also gives hints as to certain ways that plant may be used to deter certain critters, big and small.
Condensed Companion Planting Guide
Asparagus Plant plant with Aster family of flowers, basil, tomato, parsley, dill, coriander, comfrey, marigolds. Do not plant with garlic, onions, potatoes.  
Basil plant with tomatoes, peppers, oregano, asparagus, petunias; helps improve flavor and growth and aids in repelling thrips, flies, mosquitoes, deer. Do not plant with rue, sage  
Beans are wonderful to plant with most vegetables and herbs (carrots, cauliflower, celery, chards, corn, eggplant, radish, strawberry,
potatoes, cucumbers, cabbage)Beans help to enrich the soil with nitrogen Do not plant with (alliums) garlic, onions   
Beets plant with lettuce, cabbage, onions, kohlrabi, garlic, mint. Beets are good for adding minerals to the soil (leaves are made of up of 25% magnesium), valuable addition to the compost; beets flavor is improved by garlic and mint.
Do not plant with pole beans.
Broccoli is great to plant with basil, bush beans, cucumber, dill, garlic, hyssop, lettuce, marigold, mint, nasturtium, onion, potato, radish, rosemary, sage, thyme, tomato.   Celery, onions and broccoli improve broccoli’s flavor; broccoli loves calcium so pairing it with plants that don’t need calcium like nasturtiums and beets – free up the calcium in the soil for broccoli.  Do not plant with grapes, strawberries, mustards, rue.
Cabbage Family includes broccoli, Brussels sprouts, kale, kohlrabi, cauliflower, and cabbage are all wonderful when paired with celery, beets, onions, potato, spinach, chard, sage, thyme, mint, rosemary. Chamomile and cabbage improves flavor while celery and cabbage improves growth and health. Do not plant with tomatoes, strawberries, pole beans, peppers, eggplants, grapes, lettuce.  
Carrots plant with leaf lettuce, onions, peas, onions, leeks, chives, rosemary. Do not plant with dill, parsnips, Queen Ann’s lace    
Celery plant with potatoes, spinach, bush beans, onions, cabbage families, leeks, tomato, cosmos, daisies, snapdragons. Do not plant with corn, potatoes, aster. Carrots can be infected with yellow disease from aster flowers
Chards plant with beans, cabbage family, tomato, onion and roses. Do not plant with cucurbits, melons, corn or herbs  
Chives plant with carrots, tomatoes, apples, brassica family, mums, sunflowers. Improves growth & flavor of carrots and tomatoes; chives keeps aphids away, drives away Japanese beetles and carrot rustfly; Do not plant with beans and peas.
Cilantro(Chinese parsley, the seeds are coriander)   Anise, caraway, potatoes, dill. Cilantro repels harmful insects(aphids, spidermites & potato beetle)
Corn  Amaranth, white geraniums, lamb’s quarters, melons, morning glory, parsley, peanuts, pumpkin, soybeans, sunflower, potatoes, peas, beans, squash, cucumbers. Corn feeds off of the nitrogen left behind by the beans when interplanted together. Do not plant with tomatoes
Cucumber plant with beans, corn, radishes, peas, sunflower, dill, beets, nasturtiums.When planted with nasturtiums growth & flavor improve and when planted with dill it attracts predatory beneficials. Do not plant with cauliflower, potatoes, basil, sage, rue.
Eggplant plant with amaranth, beans, spinach, tarragon, thyme, marigolds, peppers        
Garlic plant with most herbs, roses, raspberries, apple trees, pear trees, celery
cucumbers, peas, and lettuce. Garlic accumulates sulfur, a natural fungicide which prevents disease. it helps in offending codling moths, Japanese beetles, root maggots, snails and carrot rootfly; time release capsules planted at the base of trees deters deer.
Lettuce plant with beets, broccoli, bush beans, pole beans, carrot, onion, strawberries,  sunflowers radishes, cucumbers, dill. Do not plant with cabbage, parsley  
Marigolds, French plant with most plants but do not plant with beans, cabbage French marigolds keeps soil free of bad nematodes and discourages many garden pests/insects.
Mint plant with cabbage, tomatoes. It improves the health of cabbage & tomatoes. While it also deters white cabbage moths, ants, rodents, flea beetles, fleas, aphids by attracting beneficials like hoverflies & predatory wasps.
Onion plant with beets, carrots, leeks, kohlrabi, brassicas, tomatoes, lettuce, strawberries, dill, chamomile, summer savory. Onions & strawberries help the berries fight disease; intercropping with leeks and onions with carrots confuses carrot & onion flies. Do not plant with peas or asparagus.  
Peas plant with corn, cucumber, celery, eggplants, bush/pole beans, radishes,
spinach, strawberries, tomatoes, turnips . Do not plant with chives, potatoes, onions, gladiolus, grapes.    
Pepper, sweet bell plant with tomatoes, okra, parsley, basil, carrots, marjoram, petunia, onions. Do not plant with fennel, kohlrabi, apricot trees  
Pepper, hot plant with cucumbers, eggplant, escarole, tomato, okra, swiss chard, squash, basil, oregano, parsley & rosemary.  Chili peppers roots exude a substance which prevents root rot and other fusarium diseases; teas made from hot peppers can be used as insect sprays  
Potato plant with bush beans, celery, carrots, corn, cabbage, horseradish, marigolds, peas, petunias, onions, French marigolds. Do not plant with asparagus, kohlrabi, rutabaga, fennel, turnip, pumpkin, squash, tomatoes, sunflowers, cucumbers    
Pumpkin plant with corn, beans, radishes, peas, oregano, marigolds, squash, melon, nasturtiums. When planted with marigolds deters beetles, planted with nasturtiums deters bugs & beetles, with oregano for the pest pest protection  
Radish plant with beets, bush beans, pole beans carrots, cucumbers, lettuce, parsnips, peas, spinach, members of squash family, nasturtium. Planted with squash helps deter squash borers; deter cucumber beetles & rust flies, chervil and nasturtiums improve radishes growth & flavor; lure leafminers away from spinach. Do not plant with hyssop, cabbage, cauliflower, Brussels sprouts, turnips.
Spinach plant with peas, beans, cauliflower, eggplant, onions, strawberries, squash, fava bean.
Squash plant with beans, pumpkins, corn, cucumbers, onions, melon, mint, borage, marigolds, oregano. When planted with borage deters worms and improves growth & flavor; marigolds deter beetles, oregano best pest protection. Do not plant with potatoes.
Strawberry plant with beans, borage, lettuce, onions, spinach, thyme. Borage strengthens resistance to insects and disease.  Do not plant with cabbage, broccoli, Brussels sprouts, cauliflower, kohlrabi.
Tomato plant with asparagus, carrots, head lettuce, mint, nasturtium, onions, beans, basil, lettuce, garlic, cucumber,celery, chives, peas, peppers, parsley, marigolds. Basil helps repel flies, mosquitoes, deer and improves growth & flavor; bee balm, chives & mint improves flavor & health of tomatoes. Do not plant with dill, fennel, apricot trees, potatoes, kohlrabi, corn.
Turnips plant with peas and cabbage. Do not plant with potatoes, radishes or other root vegetables, delphinium, larkspur, mustard.
Zucchini plant with nasturtium and flowering herbs.
It's a lot in information and I have plenty more which is why this only a consolidated companion growing guide.  We love to work with companions in our raised beds and there a wonderful way to help guide you while putting together containers.  Happy Gardening!