It’s helpful to think of building good plant communities when planning your garden. This is the most important concept behind companion planting. Time-tested garden wisdom holds that certain plants grown close together become helpmates. (See the list at the bottom.)
Plants need good companions to thrive. Except for growth and fruiting, plants are relatively idle objects. They are rooted in one spot and don’t seem to have much control over their environment. In fact, however, relationships between plants are varied - similar to relationships between people. In plant communities, certain plants support each other while others, well, just don’t get along. Plants, like people, compete for resources.
Science confirms some plants bully others. Certain plants grow rapidly, crowd others and take more than their fair share of water, sun and nutrients. Some exude toxins that retard plant growth or kill plants. A common example of this is the Black Walnut tree that produces hydrojuglone. Other plants are upstanding citizens and do good by adding nutrients to the soil, drawing beneficial insects into the garden or by confusing insects in search of their host plants.
As a gardener, you’re the both the mayor and the city planner for the city that is your garden. By growing plants with good companions, you bring peace and prosperity to your town.
As in city planning, the way your lay your vegetable garden out is crucial. Avoid planting vegetables in large patches or long rows and interplant with flowers and herbs. Large groupings of one type of vegetable serve as a beacon to problematic pests. If you mix in flowers and herbs, it becomes more difficult for pests to find your veggies. The scent of flowers and herbs, as well as the change up in color, is thought to confuse pests. Certain flowers and herbs attract beneficial insects to your garden.
Almost any article on companion planting references the Native American “Three Sister Planting”. This age old grouping involves growing corn, beans and squash – often pumpkin - in the same area. As the corn stalks grow, beans naturally find support by climbing up the stalk. Beans, as all legumes, fix nitrogen in the soil, which supports the large nutritional needs of corn. Squash grows rapidly and the large squash leaves shade out weeds and serve as natural weed block. Good plant companions work in support of each other.
Many long time gardeners swear that growing certain plants together improves flavor as well. While science hasn’t found support for some of the benefits of companion planting, there is support for the above information. Garden wisdom and experience supports these traditional beneficial plant companions.
Here are combinations found to be beneficial over time from Todd Weinmann of North Dakota State University Agriculture Extension:
|Plant||Plant Companions||Plant Allies||Plant Enemies|
|Asparagus||Basil, parsley, tomato||Pot marigold deters beetles.|
|Beans||Beet (to bush beans only), cabbage family, carrot, celery, chard, corn, cucumber, eggplant, pea, potatoes, radish, strawberry.||Marigold deters Mexican bean beetles. Nasturtium and rosemary deter bean beetles. Summer savory deters bean beetles, improves growth and flavor.||Garlic, onion and shallot stunt the growth of beans.|
|Beets||Bush beans, cabbage family, lettuce, onion.||Garlic improves growth and flavor.||Pole beans and beets stunt each other's growth.|
|Carrots||Bean, lettuce, onion, pea, pepper, radish, tomato.||Chives improve growth and flavor. Rosemary and sage deter carrot fly.||Dill retards growth.|
|Celery||Bean, cabbage family and tomato.||Chives and garlic deter aphids. Nasturtium deters bugs and aphids.|
|Chard||Bean, cabbage family and onion|
|Corn||Bean, cucumber, melon, parsley, pea, potato, pumpkin, squash.||Odorless marigold and white geranium deter Japanese beetles. Pigweed raises nutrients from the subsoil to where the corn can reach them.||Tomatoes and corn are attacked by the same worm.|
|Cucumber||Bean, cabbage family, corn, pea, radish, tomato||Marigold deters beetles. Nasturtium deters aphids, beetles and bugs, improves growth and flavor. Oregano deters pests in general. Tansy deters ants, beetles, bugs, flying insects.||Sage is generally injurious to cucumber.|
|Eggplant||Bean, pepper.||Marigold deters nematodes.|
|Lettuce||Beet, cabbage family, carrot, onion, radish, strawberry.||Chives and garlic deter aphids.|
|Melons||Corn, pumpkin, radish, squash.||Marigold deters beetles. Nasturtium deters bugs and beetles. Oregano provides general pest protection.|
|Onions||Beet, cabbage family, carrot, chard, lettuce, pepper, strawberry, tomato.||Chamomile and summer savory improve growth and flavor. Pigweed raises nutrients from subsoil and makes them available to the onions. Sow thistle improves growth and health.||Onions stunt bean, pea.|
|Parsley||Asparagus, corn, tomato|
|Peas||Bean, carrot, corn, cucumber, radish, turnip.||Chives deter aphids. Mint improves health and flavor.||Garlic and onion stunt the growth of peas.|
|Peppers||Carrot, eggplant, onion and tomato|
|Potatoes||Beans, cabbage family, corn, eggplant, pea.||Horseradish, planted at the corners of the potato patch, provides general protection. Marigold deters beetles.||Tomatoes and potatoes are attacked by the same blight.|
|Pumpkins||Corn, melon, squash.||Marigold deters beetles. Nasturtium deters bugs, beetles. Oregano provides general pest protection.|
|Radishes||Bean, carrot, cucumber, lettuce, melon, pea.||Chervil and nasturtium improve growth and flavor.||Hyssop|
|Spinach||Cabbage family, strawberry|
|Squash||Corn, melon, pumpkin.||Borage deters worms, improves growth and flavor. Marigold deters beetles. Nasturtium deters squash bugs and beetles. Oregano provides general pest protection.|
|Strawberry||Bean, lettuce, onion, spinach, thyme.||Cabbage.||Borage strengthens resistance to insects and disease. Thyme, as a border, deters worms.|
|Tomatoes||Asparagus, carrot, celery, cucumber, onion, parsley, pepper.||Basil repels flies and mosquitoes, improves growth and flavor. Bee balm, chives and mint improve health and flavor. Borage deters tomato worm, improves growth and flavor. Dill, until mature, improves growth and health. Once mature, it stunts tomato growth. Marigold deters nematodes. Pot marigold deters tomato worm and general garden pests.||Corn and tomato are attacked by the same worm. Mature dill retards tomato growth. Kohlrabi stunts tomato growth. Potatoes and tomatoes are attacked by the same blight.|
|Cabbage Family (Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Chinese Cabbage, Kale, and Kohlrabi)||Beet, celery, chard, cucumber, lettuce, onion, potato, spinach.||Chamomile and garlic improve growth and flavor. Catnip, hyssop, rosemary and sage deter cabbage moth. Dill improves growth and health. Mint deters cabbage moth and ants, improves health and flavor. Nasturtium deters bugs, beetles, aphids. Southernwood deters cabbage moth, improves growth and flavor. Tansy deters cabbageworm and cutworm. Thyme deters cabbageworm.||Kohlrabi and tomato stunt each other's growth.|