Companion planting is the placement of various crops in close physical proximity to one another so as to symbiotically compliment each others progress. One traditional practice was interplanting corn and pole beans. The cornstalk would serve as a trellis for the beans. The beans fixed Nitrogen for the corn. The squash serves as a living mulch and completes the Three Sisters technique, pioneered by Native Americans.
Companion planting was widely touted in the 70s as part of the organic gardening movement. It was encouraged not only for pragmatic reasons like trellising, but rather with the idea that different plants may thrive more when close together.
It is also a technique used in permaculture, along with mulching, polyculture, and crop rotation. The combinations of plants also makes for a varied, attractive vegetable garden. Avoid monoculture. Where the same plant is grown in rows or large groups. Monoculture attracts pests and diseases to their preferred crops and enhances their spread.
Many of the modern principles of companion planting were present many centuries ago in cottage gardens. Companion plants can benefit each other in a number of different ways, including:
Flavor enhancement Some plants, especially herbs, seem to subtly change the flavor of other plants around them.
Hedged investment Multiple plants in the same space increase the odds of some yield being given, even if one category encounters catastrophic issues.
Level interaction Plants which grow on different levels in the same space, perhaps providing ground cover or working as a trellis for another plant.
Ferilization Primarily nitrogen fixation plants, such as beans and legumes fix nitrogen in the ground, making it available to other plants. Plants, such as Borage add trace minerals.
Pest suppression Plants which repel insects, plants, or other pests like nematodes or fungi, through chemical means. Pest Suppression is also relative to Trap Cropping, plants which attract pests away from others.
Positive hosting Attracts or is inhabited by insects or other organisms which benefit plants, as with ladybugs or some “good nematodes”.
Protective shelter One type of plant may serve as a wind break, or shade from noonday sun, for another.
Most companion planting guidelines are steeped in myths handed down from generation to generation ,conjecture, and personal observations with no considerations to multiple variables. Basically there is little documented scientific support. Plant relationships are parroted from one site to another.
Whenever at all possible, we attempt to provide the rationale behind plant relationships. Please keep in mind that many inter-actions are also percentage based. If an insect that attacks a certain garden plant is repelled by another type of plant – that doesn’t mean that absolutely no insects of the genus in question will go near the plants in question – it simply means a much lower percentage than normally would have attacked the plant will show up.
Thank You for taking the time to read this. Happy Gardening