Companion planting

Gardens can be full of friends.

People plant different crops close together. This helps the plants grow well.

Some plants help keep bugs away. Onions have a smell. This smell keeps flies away from carrots.

Carrots have a smell too. It keeps onion flies away.

Plants can also help the soil. Some plants take food from the air. This food helps the plants nearby grow big.

Other plants give shade. This keeps the soil cool and wet. This is good for the plants.

It is a smart way to farm. It helps plants stay healthy and strong.

Companion planting is a way to grow different crops close together.

This helps plants grow better. It can stop weeds. It can also help control pests.

Some plants work like a team. Long ago, people in the Americas used the Three Sisters method. They grew corn, beans, and squash together. The corn gave beans a tall pole to climb. The beans put nitrogen, a plant food, into the soil. The big squash leaves gave shade to keep the soil moist.

In China, people used mosquito ferns to help rice grow. These ferns take nitrogen from the air.

Smells can also protect a garden. The smell of onions can keep carrot flies away. The smell of carrots can keep onion flies away.

Some plants act as decoys. They attract bugs away from the main food. Other plants attract "good" bugs. These are insects that eat the pests. For example, spearmint attracts a bug called the mirid bug. This bug helps keep the garden safe.

Some crops even need shade. Coffee plants often grow under trees to stay cool.

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Instead of growing just one thing, farmers use many plants together to help them thrive. This method is a form of polyculture, which means growing more than one type of plant in the same space. People do this for many helpful reasons. It can stop weeds from growing or help plants get more food from the soil. It can also attract helpful insects or provide shade. By working together, these plants can increase how much food a garden produces.

\n\nThere are many ways these plant teams work. Some plants, called legumes, have special bumps on their roots called nodules.

These nodules help the plant take nitrogen from the air and put it into the soil. This acts like natural food for the plants growing nearby. Other plants act as decoys or \"trap crops.\" For example, some gardeners plant nasturtiums to attract caterpillars away from cabbage. This keeps the cabbage safe from being eaten. Some plants even use smells to protect their neighbors. The scent of marigolds can stop certain pests from feeding on nearby plants.

\n\nPeople have used these ideas for a very long time. Thousands of years ago in Mesoamerica, indigenous peoples used the \"Three Sisters\" method. They grew corn, beans, and squash together as a team. The corn provided a tall pole for the beans to climb. The beans added nitrogen to the soil to help the corn grow. The wide squash leaves covered the ground to keep the soil moist.

In China, people have used mosquito ferns to help rice crops for at least a thousand years. These ferns help by adding nitrogen to the rice plants. Even in ancient Greece and Rome, writers noticed how some plants could affect others. For instance, Pliny the Elder wrote that walnut trees could poison other plants nearby.\n\nModern gardeners and farmers still use these rules today. Since the 1920s, organic farmers have used companion planting to avoid using artificial chemicals. They use many things like vegetables, fruit trees, and herbs. Some plants are great at attracting \"good\" bugs that eat the "bad" pests. For example, planting cornflowers among cabbage helps a tiny wasp called Microplitis mediator. This wasp hunts the moths that try to eat the cabbage.

Other herbs like spearmint can attract the mirid bug to help protect crops.

Scientists are still studying these complex relationships to learn even more.\n\nYou can see these ideas in many places around the world. Some people use \"forest gardening\" to mimic how a natural woodland works. This involves growing plants at many different heights. Others use \"square foot gardening\" to pack plants closely together. You might even see it in coffee plantations. In places like Costa Rica, coffee bushes often grow under the shade of taller trees. This protects the coffee from getting too hot in the sun. Whether in a small backyard or a huge farm, companion planting helps nature work together.", "media": [ "File:Companion Planting Mechanisms.svg", "File:Companion Planting Interactions.svg", "File:Medicago sativa root nodules.JPG", "File:KarottenZwiebeln 266.JPG", "File:Coffee shadow trees costa rica.jpg", "File:Microplitis mediator adult female.jpg", "File:Nesiocoris tenuis on leaf.jpg" ] }

Companion planting is a method of polyculture used in gardening and small-scale agriculture. It involves planting different crops in close proximity to achieve specific benefits. These benefits include weed suppression, pest control, and improved pollination. It can also provide habitats for beneficial insects and maximize the use of space. By using these methods, farmers may increase their total crop productivity. This approach can also reduce the need for expensive artificial fertilizers and pesticides.

The biological mechanisms behind companion planting are diverse and complex. One primary method is nutrient provision through nitrogen fixation. Legumes, such as clover, host symbiotic bacteria in their root nodules.

These bacteria take nitrogen from the atmosphere and convert it into compounds in the soil. This process provides natural fertilizer for neighboring plants, such as grasses. Another mechanism is trap cropping, where alternative plants attract pests away from the main crop. For example, nasturtium plants may attract caterpillars that would otherwise eat members of the Brassicaceae family.

Plants can also use chemical or physical ways to manage pests. Some plants are allelopathic, meaning they produce chemicals that affect other species. Rye is a cereal crop that can act as a cover crop to suppress weeds. It produces phytotoxic substances called DIBOA and BOA, which inhibit the growth of nearby seedlings. Other plants use aromatic volatile compounds to mask the scent of a target crop. For instance, the smell of onions may deter the carrot root fly. Conversely, the scent of carrots may deter the onion fly.

Another important strategy is host-finding disruption. Insects often find host plants by detecting specific odors in the air. If a target plant is surrounded by "decoy" plants or green ground cover, pests may experience "inappropriate landings." Research showed that 36% of cabbage root flies laid eggs in bare soil. However, only 7% laid eggs when cabbages were grown with clover ground cover. This disruption makes it harder for flying pests to locate their intended food source. Some companion plants also act as insectary plants by producing nectar and pollen. These plants recruit predators, such as the mirid bug attracted to spearmint.

The history of these practices spans thousands of years across many cultures. In Mesoamerica, indigenous peoples developed the "Three Sisters" technique. They grew maize, common beans, and squash together in a functional system. The cornstalk acted as a trellis for the beans to climb. The beans fixed nitrogen to benefit the maize. The wide leaves of the squash provided shade to keep the soil moist.

In China, mosquito ferns have been used with rice for at least a thousand years. These ferns host the bacterium Anabaena azollae, which fixes nitrogen and blocks light from competing plants.

Ancient writers also documented these plant interactions. About 2000 years ago, Theophrastus noted that bay trees and cabbage could weaken grapevines. Pliny the Elder observed that the shade of the walnut tree could poison other plants. In the 20th century, organic farming and permaculture revitalized these methods. Since the 1920s, these techniques have been vital where chemical inputs are restricted. Modern agronomists now suggest a multitrophic approach for sustainable crop protection. This involves managing interactions between crops, companion plants, pests, and natural enemies.

While many interactions are beneficial, they are not always predictable. Some combinations can actually fail to protect a crop. For example, French marigold inhibits the codling moth, which destroys apples. However, it also inhibits the moth's natural enemy, the parasitoid wasp Ascogaster quadridentata. This can result in no actual reduction in apple damage. Similarly, a 2019 study in Brazil found that parsley helped suppress aphids in collard greens. Yet, it also reduced the number of parasitoid wasps because predatory insects ate them. These complex biological webs show why companion planting requires careful study.