Companion planting is a form of intercropping which intends to create mutually beneficial relationships between neighboring plants. Different species have a variety of possible interactions. For example, some plants' roots secrete different growth inhibitors and promotors, making a neighbouring crop grow worse or better. Plants are chosen as companion plants for the functions that they can provide, which can be grouped into the following categories: dynamic accumulators, edible nitrogen fixing species, green manures, weed inhibiting plants and weed barrier plants. Besides providing nutrients and suppressing weeds, there are also other possible benefits such as more efficient space utilization, higher yields, improvement of the flavour of the harvested products, wind sheltering, etc. The combinations of plants also make for a more varied, attractive vegetable garden.
One of the earliest examples of companion planting we have today is that of the Native American peoples, who planted corn and pole beans together. The cornstalk would become a trellis for the beans to climb up. With the addition of squash, they pioneered what became the Three Sisters technique. Many of the modern principles of companion planting were present many centuries ago in the cottage garden. Companion planting was widely touted in the 1970s as part of the organic gardening movement. It was encouraged not for pragmatic reasons like trellising, but rather with the idea that different species of plant may thrive more when close together.
Examples[edit | edit source]
Nasturtiums are well-known to attract caterpillars, so planting them alongside or around vegetables such as lettuce or cabbage will protect them, as the egg-laying insects will tend to prefer the nasturtium.
The use of plants that produce copious nectar and protein-rich pollen in a vegetable garden is a good way to enhance the population of beneficial insects that control pests. Some insects in the adult form are nectar or pollen feeders, while in the larval form they are voracious predators of pest insects.
Pungent or a brightly-colored crops can repel pests. Trap crops may distract pests another crop. These include:
- Onions (smell) with cabbage
- Marigold with ground nuts and peas (colour, smell repels pests)
- Coriander (smell)
- Mint plant (smell)
- Other herbs (smell)
- Garlic around fruit trees - Repels Borers
- Garlic around tomatoes - Repels red spider mites
- Traditional practice of planting garlic bulbs under Roses to repel pests