Companion planting
From Wikipedia, the free encyclopedia
Companion planting is the planting of different crops in close physical 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.
Although there is a wealth of information on its historic use, there remains limited available scientific research on the effectiveness for each of these interventions.[1] [2] [3] [4]
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 the cottage garden.
For farmers utilizing an Integrated Pest Management system, increased yield and/or reduction of pesticides is the goal[citation needed].
In the developing world, tropical crops are used instead of temperate ones and provide NGOs and other organizations a tool for alleviating poverty[citation needed].
For gardeners, the combinations of plants also make for a more varied, attractive vegetable garden. It can also be used to mitigate the decline of biodiversity.[citation needed]
Companion planting is considered to be a form of polyculture[citation needed].
Contents |
[edit] In history
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.
One traditional practice of Native Americans was 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.
[edit] Examples of companion 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[citation needed]. This practice is called trap croping.
Marigolds assist crops suffering from aphids (greenfly among others) through their smell being deterrent to aphids and attractant to hoverflies (a predator of aphids)[citation needed]. Marigolds are also said[weasel words] to deter other pests[which?].
[edit] 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.
[edit] 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.
[edit] 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.
This is one of the reasons why monoculture is counter-productive: pesticides effectively immunized the pests more and more, generation after generation, while still providing ample shelter and food for these.
Source: [1]Horticulture Research International, Wellesbourne : “Insects can see clearly now the weeds have gone.” Finch, S. & Collier, R. H. (2003). Biologist, 50 (3), 132-135.
[edit] Companion plant categories
Companion plants can benefit each other in a number of different ways, including:[5]
- Flavor enhancement — some plants, especially herbs, seem to subtly change the flavor of other plants around them[citation needed].
- 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
- 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"
- 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.
