Companion planting is sometimes considered the front runner of organic gardening, the reasons for which are obvious in the garden. Gardeners have been planting certain types of plants together as companions for centuries. The benefits of companion planting are natural insect repellents, shade and windbreaks, and to discourage animals that are harmful in the garden like rabbits dogs and cats. Some plants, like legumes, release nitrogen into the soil which decreases the need for yearly fertilization and provide needed nitrogen to its neighbors. Another benefit to companion planting is spacing: growing tall and vining plants in the same patch can free up valuable real estate in the garden.
Ward off insects by planting strong smelling crops next to mild crops, like tomatoes and onion next to cabbage, carrots and celery. Onions are also good companions to beets, cucumbers, lettuce, peppers, squash and strawberries.
Repel flying insects with the use of colors. Plant nasturtium next to cabbage, cucumbers, melons, radish, squash and tomatoes. Plant marigolds next to bush and pole beans, the cabbage family, cucumbers, strawberries and tomatoes.
Provide shade to corn roots with melons and cucumbers. The corn will in turn provide shade to the fruiting vines below.
Deter Mexican bean beetles and nematodes with marigolds, which can and should be planted throughout and around the border of the garden. Potted marigolds keep dogs out of the garden. Use Rosemary to keep cabbage moths, carrot fly and bean beetles away.
Grow onions, garlic and chives mixed in with leafy green plants to keep rabbits from feasting on your lettuce and such.