The Three Sisters Garden garden of corn, beans, and squash is a good example of companion planting. The beans fix nitrogen in the soil, helping to feed the corn and squash plants.
Plants, like people, have certain likes and dislikes when it comes to companions. Companion planting is a long-held idea that certain plants benefit each other when grown in close proximity. While this technique has been used for centuries in many traditional agricultural communities, companion planting has mixed results when scientifically tested. But certain aspects of companion planting are well understood. For example, legumes such as beans and peas fix atmospheric nitrogen into a form that plants can use. This works to the advantage of crops growing nearby. The traditional Three Sisters Garden of corn, beans, and squash works well because the beans add nitrogen to the soil that the corn and squash use to grow. It's also known that some plants exude chemicals to repel insects or inhibit the growth of other plants. Walnut trees give off juglone from their roots that inhibits the growth of certain plants, such as tomatoes, growing nearby. African marigolds emit the chemical thiopene from their roots, which has been proven to repel nematodes. Companion plants can also be used as trap crops. The concept involves growing one plant that is especially desirable to an insect pest in order to lure insects away from another crop you are trying to protect. The bugs congregate on the trap crop and are easier to control. For example, Blue Hubbard winter squash has been used to draw cucumber beetles away from summer squash.
Maximize your planting space by growing vining crops, such as cucumbers, around climbing crops, such as pole beans.
However, beyond these examples, many companion planting techniques are based on personal gardening experiences rather than scientific studies. While it may not be clear why a crop grows better in close proximity to one plant than another, there are many combinations that have been discovered over the years that seem to have some benefit. One of the most famous proponents of companion planting was Louise Riotte. In her famous books, Carrots Love Tomatoes and Roses Love Garlic, (Storey Books), written in the 1970s and still in print, she describes many of the companion planting combinations that work best. These not only include plants that grow well together, but also ones that should be separated because they are antagonistic.
Below is a chart from the National Sustainable Agriculture Information Service summarizing some of the common companion planting combinations that gardeners might use. Give some of these combinations a try and let me know what happens in your garden.
|Asparagus||Tomato, Parsley, Basil||--|
|Beans||Most Vegetables & Herbs||--|
|Beans, Bush||Irish Potato, Cucumber, Corn, Strawberry, Celery, Summer Savory||Onion|
|Beans, Pole||Corn, Summer Savory, Radish||Onion, Beets, Kohlrabi, Sunflower|
|Cabbage Family||Aromatic Herbs, Celery, Beets, Onion Family, Chamomile, Spinach, Chard||Dill, Strawberries, Pole Beans, Tomato|
|Carrots||English Pea, Lettuce, Rosemary, Onion Family, Sage, Tomato||Dill|
|Celery||Onion & Cabbage Families, Tomato, Bush Beans, Nasturtium||--|
|Corn||Irish Potato, Beans, English Pea, Pumpkin, Cucumber, Squash||Tomato|
|Cucumber||Beans, Corn, English Pea, Sunflowers, Radish||Irish Potato, Aromatic Herbs|
|Lettuce||Carrot, Radish, Strawberry, Cucumber||--|
|Onion Family||Beets, Carrot, Lettuce, Cabbage Family, Summer Savory||Beans, English Peas|
|Pea, English||Carrots, Radish, Turnip, Cucumber, Corn, Beans||Onion Family, Gladiolus, Irish Potato|
|Potato, Irish||Beans, Corn, Cabbage Family, Marigolds, Horseradish||Pumpkin, Squash, Tomato, Cucumber, Sunflower|
|Pumpkins||Corn, Marigold||Irish Potato|
|Radish||English Pea, Nasturtium, Lettuce, Cucumber||Hyssop|
|Spinach||Strawberry, Fava Bean||--|
|Squash||Nasturtium, Corn, Marigold||Irish Potato|
|Tomato||Onion Family, Nasturtium, Marigold, Asparagus, Carrot, Parsley, Cucumber||Irish Potato, Fennel, Cabbage Family|
|Turnip||English Pea||Irish Potato|
Another way to grow plants together for their mutual benefit is a better understood technique called interplanting. Interplanting uses the plants natural growth pattern to match crops together and maximize the space in the garden. Farmers have used interplanting systems for years to increase production and decrease erosion. For example, corn and soybeans are often grown either in strips or even together to increase yields. Interplanting also can be used to attract beneficial insects to the garden to help ward off harmful insects. In general, the more diversity of plants in your garden, the fewer problems you'll have with pests.
In the home garden, you can use interplanting, not so much to maximize yields, but to save space and plant more vegetables. Often it's a matter of matching a slow growing, large vegetable plant with a faster growing, smaller crop. The slow growing, large crop requires wide spacing between plants to accommodate its eventual size. Small, fast growing crops can be grown in the spaces between individual large plants, maturing before the larger plants shade them out. Some examples of slow and fast maturing vegetables are listed below.
Kale is a fast maturing, cool season vegetable that grows well intercropped with pole beans or tomatoes.
Larger, Slow Growing Vegetables: Peas, onions, parsnip, corn, tomatoes, peppers, eggplant, squash, cabbage, broccoli, pole beans, and Brussels sprouts.
Smaller, Fast Maturing Vegetables: Lettuce, mesclun, spinach, beets, kale, Swiss chard, radish.
Some examples of combinations that you might try include:
More great information on companion and interplanting