Companion planting

Companion planting is the planting of different crops in proximity (in gardening and agriculture), on the theory that they assist each other in nutrient uptake, pest control, pollination, and other factors necessary to increasing crop productivity. Companion planting is a form of polyculture.

Companion planting is used by farmers and gardeners in both industrialized and developing countries for many reasons. Many of the modern principles of companion planting were present many centuries ago in cottage gardens in England and home gardens in Asia.

For farmers using an integrated pest management system, increased yield and/or reduction of pesticides is the goal.^{[citation needed]} For gardeners, the combinations of plants also make for a more varied, attractive vegetable garden, as well as allowing more productive use of space.

History

In China, the mosquito fern has been used for at least one thousand years, as a companion plant for rice crops. It hosts a special cyanobacteria that fixes nitrogen from the atmosphere, and also blocks out light from getting to any competing plants, aside from the rice, which is planted when tall enough to stick out of the water above the azolla layer.^{[citation needed]}

Companion planting was practiced in various forms by Native Americans prior to the arrival of Europeans. One common system was the planting of corn (maize) and pole beans together. The cornstalk would serve as a trellis for the beans to climb while the beans would fix nitrogen for the corn. The inclusion of squash with these two plants completes the Three Sisters technique, pioneered by Native American peoples.^{[citation needed]}

Companion planting was widely touted in the 1970s as part of the organic gardening movement.^{[citation needed]} It was encouraged for pragmatic reasons, such as natural trellising, but mainly with the idea that different species of plant may thrive more when close together.^{[citation needed]} It is also a technique frequently used in permaculture, together with mulching, polyculture, and changing of crops.

Examples of companion plants

See also: List of companion plants, List of beneficial weeds, and List of repellent plants

Nasturtium are well-known to attract caterpillars, therefore, planting them around vegetables such as lettuce or cabbage protects them from damage, as egg-laying insects will tend to prefer the nasturtium.^[1] This practice is called trap cropping.

Marigolds assist crops suffering from aphids (greenfly among others) through their smell deterring to aphids and attracting hoverflies (a predator of aphids)^{[citation needed]}.

Versions

There are a number of systems and ideas using companion planting.

Square foot gardening, for example, attempts to protect plants from many normal gardening problems by packing them as closely together as possible, which is facilitated by using companion plants, which can be closer together than normal.

Another system using companion planting is the forest garden, where companion plants are intermingled to create an actual ecosystem, emulating the interaction of up to seven levels of plants in a forest or woodland.

Organic gardening often depends on companion planting for its best performance, since so many synthetic means of fertilizing, weed reduction, pest control, and other garden needs are forbidden.

Good weeds

There are many beneficial weeds, which can be allowed to grow alongside plants, imparting the same kinds of benefits as mixing cultivated crops.

Host-finding disruption

Recent studies on host-plant finding have shown that flying pests are far less successful if their host-plants are surrounded by any other plant or even "decoy-plants" made of green plastic, cardboard, or any other green material.

The host-plant finding process occurs in phases:

• The first phase is stimulation by odours characteristic to the host-plant. This induces the insect to try to land on the plant it seeks. But insects avoid landing on brown (bare) soil. So if only the host-plant is present, the insects will quasi-systematically find it by simply landing on the only green thing around. This is called (from the point of view of the insect) "appropriate landing". When it does an "inappropriate landing", it flies off to any other nearby patch of green. It eventually leaves the area if there are too many 'inappropriate' landings.
• The second phase of host-plant finding is for the insect to make short flights from leaf to leaf to assess the plant's overall suitability. The number of leaf-to-leaf flights varies according to the insect species and to the host-plant stimulus received from each leaf. The insect must accumulate sufficient stimuli from the host-plant to lay eggs; so it must make a certain number of consecutive 'appropriate' landings. Hence if it makes an 'inappropriate landing', the assessment of that plant is negative, and the insect must start the process anew.

Thus it was shown that clover used as a ground cover had the same disruptive effect on eight pest species from four different insect orders. An experiment showed that 36% of cabbage root flies laid eggs beside cabbages growing in bare soil (which resulted in no crop), compared to only 7% beside cabbages growing in clover (which allowed a good crop). Simple decoys made of green cardboard also disrupted appropriate landings just as well as did the live ground cover.^[2]

Companion plant categories

Companion plants can benefit each other in a number of different ways, including:^[3]

• Flavor enhancement — some plants, especially herbs, seem to subtly change the flavor of other plants around them.^[4]
• Hedged investment — multiple plants in the same space increase the odds of some yield being given, even if one category encounters catastrophic issues
• Increased level interaction — plants that grow on different levels in the same space, perhaps providing ground cover or working as a trellis for another plant
• Nitrogen fixation — plants that fix nitrogen in the ground, making it available to other plants
• Pest suppression — repelling pest insects, weeds, nematodes, or pathogenic fungi, through chemical means .^[4]
• Pollinator and predator recruitment — The use of plants that produce copious nectar and protein-rich pollen in a vegetable garden (insectary plants) is a good way to recruit higher populations 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.
• Positive hosting — attracts or is inhabited by beneficial insects or other organisms which benefit plants, as with ladybugs or some "good nematodes".^[4]
• Protective shelter — one type of plant may serve as a wind break or shade for another
• Trap cropping — plants that attract pests away from others
• Pattern disruption — in a monoculture, pest spread from one plant to the next, is interrupted by companion plants.^[2]

See also

• Satoyama
• Intercropping

References

1. ^ "Pest control / Companion planting". Notcutts. October 27, 2010. http://blog.notcutts.co.uk/latest-articles/2010/10/27/pest-control-companion-planting.html. Retrieved 2010-27-10. 
2. ^ ^{a b} Horticulture Research International, Wellesbourne : "Insects can see clearly now the weeds have gone". Finch, S. & Collier, R. H. (2003). Biologist, 50 (3), 132-135
3. ^ "Notes on Natural Pest Control for an Organic Garden on DigGood.com". http://www.didgood.com/health/naturalpestcontrol.html. 
4. ^ ^{a b c} "The Self-Sufficient Gardener Podcast--Episode 24 Companion Planting and Crop Rotation". http://theselfsufficientgardener.com/episode-24-companion-planting-and-crop-rotation/. Retrieved 2010-08-13. 

External links

• Companion planting: A chemical-free way to repel pests with plants Jessica Damiano
• A companion planting table
• Companion Planting at Golden Harvest Organics