EVER heard of companion planting? It is based around the idea that certain plants can benefit others when planted next to, or close to one another. It exists to benefit certain plants by giving them pest control, naturally without the need to use chemicals, and in some cases they can give a higher crop yield.

Companion planting, considered to be a form of polyculture, is used by farmers and gardeners in both industrialized and developing countries for many reasons.

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Researchers have proven that by having a beneficial crop in a nearby field that attracts certain insects away from a neighboring field that has the main crop can prove very beneficial.

Companion planting exists in a physical way. For example, tall-growing, sun-loving plants may share space with lower-growing, shade-tolerant species, resulting in higher total yields from the land.

Planting tall or dense-canopied plants may protect more vulnerable plants through shading or by providing a windbreak. In some instances, the benefit is derived when companion plants provide a good environment for beneficial insects, and other arthropods, especially those predatory and parasitic species that help to keep pest populations in check.

Other ways that companion planting can be beneficial is to plant a crop like legumes on an area where it will feed nitrogen into the soil, then it will not be necessary to use any chemical fertilizers for the next crop.

Unfortunately, there are other plants that slow down each other's growth. These crops should not be grown together. Experts call this phenomenon as antagonistic planting.

Now, here's a list of vegetable crops with their companion plants and antagonistic plants (culled from various sources):

Amaranth: A tropical annual that needs hot conditions to flourish. Good with sweet corn; its leaves provide shade giving the corn a rich, moist root run. Also, amaranth is host to predatory ground beetles.

Ampalaya: This all-year round vegetable can be grown along with trellised lima bean, yard-long bean, and winged bean.

Asparagus: Friend of tomato, parsley, basil, and marigold. Avoid planting asparagus with onion, garlic and potato.

Basil: Plant with tomato to improve growth and flavor. Basil also does well with peppers, oregano, asparagus and petunias. It can be helpful in repelling thrips. Basil is said to repel flies and mosquitoes.

Beans: All beans enrich the soil with nitrogen fixed from the air. Generally, they are good company for carrot, celery, corn, eggplant, peas, potato, beets, radish, and cucumber. Beans are great for heavy nitrogen users like corn because beans fix nitrogen from the air into the soil so the nitrogen used up by the corn are replaced at the end of the season when the bean plants die back. Keep beans away from the alliums.

Cabbage: Potato, celery, dill, and onion are good companion plants. Celery improves growth and health. It does not get along with tomato, peppers, eggplant, grapes and pole sitao.

Carrot: Its pals are leaf lettuce, leek, peas, onion and tomato. Keep dill away from carrot. One drawback with tomato and carrot when planted together: tomato plants can stunt the growth of the carrots but the latter will still be of good flavor.

Cassava: It gets along well with sweet potato, swamp cabbage, pechay, alugbati, lettuce, garlic, golden squash, and peanut.

Celery: Among its companions are beans, cabbage, leek, onion, and tomato. Its foe: corn.

Corn: Grown best with amaranth, beans, cucumber, melons, parsley, peanut, peas, potato, soybean, squash, and sunflower. Keep corn away from celery and tomato plants.

Cucumber: Cucumber is great to plant with corn and beans. The three plants like the same conditions: warmth, rich soil and plenty of moisture. Let the cucumbers grow up and over the corn plants. A great duet is to plant cucumber with sunflower. The sunflower provides a strong support for the vines. Cucumber also does well with peas, beets, radish, and carrot. Radish is a good deterrent against cucumber beetles. Dill planted with cucumbers helps by attracting beneficial predators. Keep potato away from cucumber.

Eggplant: Plant with amaranth, beans, peas, swamp cabbage, golden squash, radish, and marigold. Eggplant is a member of the nightshade family and does well with peppers. Avoid planting potato near eggplant.

Garlic: This spice crop accumulates sulfur: a naturally occurring fungicide which will help in the garden with disease prevention. Garlic is systemic in action as it is taken up the plants through their pores and when garlic tea is used as a soil drench it is also taken up by the plant roots.

Lettuce: Does well with beet, bush bean, pole bean, cabbage, carrot, cucumber, onion, and radish. It grows happily in the shade under young sunflowers.

Onion: Planting chamomile with onion improves the former's flavor. Other companions: carrot, leek, beet, dill, lettuce, and tomato. Intercropping onion and leek with your carrot confuses the carrot and onion flies! Keep onion away from peas, beans, and asparagus.

Peas: Companions for peas are bush beans, pole beans, carrots, celery, corn, cucumber, eggplant, parsley, radish, and sweet pepper. Do not plant peas with onion, garlic, and potato.

Potato: The following may be planted with potato: bush bean, cabbage, carrot, celery, corn, marigold, peas, and onion. Don't plant these around potato: asparagus, cucumber, squash, and sunflower. Keep potato and tomato apart as they both can get early and late blight contaminating each other.

Tomato: Grown along with asparagus, parsley, cabbage, onion, radish, garlic and carrot. Tomato protects asparagus from asparagus beetles while asparagus protects tomato from nematodes. Planted with garlic, the latter repels red spider mite. Don't grow potato and tomato with each other; potato inhibits tomato growth while tomato renders potato more susceptible to blight.