Companion gardening is the planting together of plants that have similar growing needs, to maximize the production of both plants. It is still an experimental field with more research needed, but there are some things we do know and can pass along.
Plants, like people, sometimes like or dislike each other, depending on their natures. As plants grow, they begin to relate to the plants around them. And just like people, plants develop distinct personalities, which show up as aromas, pollens, and other essences that are given off around them. Beneficial relationships can develop due to proximity to one another, crop rotation and flowers that attract certain insects.
As an example, green beans and strawberries grow better when they are grown together than when they are grown separately.
To get really good tasting Bibb lettuce, plant one spinach plant for every 4 Bibb lettuce plants.
Even weeds have really good instincts, which is demonstrated by the fact that they take well to sick soil where cultivated crops have difficulty thriving. Dandelions have beneficial effects by increasing the aromatic qualities of herbs and improving the potash level of vegetables (a good thing).
Certain plants benefit the entire plant community:
- Lemon Balm, Marjoram, Oregano, Stinging Nettle, and Chamomile are among these beneficial plants;
- Marigolds are the workhorse of pest deterrents. They discourage Mexican bean beetles, nematodes, and other insects.
- Garlic is good planted near roses and raspberries for their growth and deterring Japanese beetles;
- Chives are a good companion to carrots and tomatoes but are not good next to peas and beans;
- Dill improves the health and growth of cabbage, but is not liked by carrots;
- Bush Beans are good companions for cucumbers, corn, strawberries and celery, but are antagonistic to onions.
For a more complete list of common plants and their companions, see “Companion Plants and How to Use Them” by Helen Philbrick and Richard B. Gregg.