Companion Gardening Companion planting, or companion gardening is the practice of planting two different plants in close proximity to each other on the theory that they help each other in some way. Some plants complement each other, giving off by products that the other plant needs. Those by products are chemicals and micro-nutrients. Other beneficial plants provide some protection against insects and planting a few of them near a desired plant will keep the insects away.
Foundations for Companion Planting
Trap cropping
Sometimes, a neighboring crop may be selected because it is more attractive to pests and serves to distract them from the main crop. An excellent example of this is the use of collards to draw the diamond back moth away from cabbage.
Symbiotic nitrogen fixation
Legumes—such as peas, beans, and clover—have the ability to capture atmospheric nitrogen for their own use and for the benefit of neighboring plants via symbiotic relationship with Rhizobium bacteria. Forage legumes, for example, are commonly seeded with grasses to reduce the need for nitrogen fertilizer. Likewise, beans are sometimes interplanted with corn.
Biochemical pest suppression
Some plants exude chemicals from roots or aerial parts that suppress or repel pests and protect neighboring plants. The African marigold, for example, releases thiopene—a nematode repellent—making it a good companion for a number of garden crops. The manufacture and release of certain biochemicals is also a factor in plant antagonism. Allelochemicals such as juglone—found in black walnut— suppress the growth of a wide range of other plants, which often creates a problem in home horticulture. A positive use of plant allelopathy is the use of mow-killed grain rye as a mulch. The allelochemicals that leach from rye residue prevent weed germination but do not harm transplanted tomatoes, broccoli, or many other vegetables.
Physical spatial advantages
For example, tall-growing, sun-loving plants may share space with lower-growing, shade-tolerant species, resulting in higher total yields from the land. Spatial interaction can also yield pest control benefits. The diverse canopy resulting when corn is companion-planted with squash or pumpkins is believed to confuse the adult squash vine borer and protect the vining crop from this damaging pest. In turn, the presence of the prickly vines is said to discourage raccoons from ravaging the sweet corn.
Nurse cropping
Tall or dense-canopied plants may protect more vulnerable species through shading or by providing a windbreak. Nurse crops such as oats have long been used to help establish alfalfa and other forages by supplanting the more competitive weeds that would otherwise grow in their place. In many instances, nurse cropping is simply another form of physical-spatial interaction.
Beneficial habitats
Beneficial habitats—sometimes called refugia—are another type of companion plant interaction that has drawn considerable attention in recent years. The benefit is derived when companion plants provide a desirable environment for beneficial insects and other arthropods—especially those predatory and parasitic species which help to keep pest populations in check. Predators include ladybird beetles, lacewings, hover flies, mantids, robber flies, and non-insects such as spiders and predatory mites. Parasites include a wide range of fly and wasp species including tachinid flies, and Trichogramma and ichneumonid wasps. Agroecologists believe that by developing systems to include habitats that draw and sustain beneficial insects, the twin objectives of reducing both pest damage and pesticide use can be achieved.
Table
1. COMPANION PLANTING CHART
FOR HOME & MARKET GARDENING
(compiled from traditional literature on
companion planting)
|
|
CROP
|
COMPANIONS
|
INCOMPATIBLE
|
| Asparagus |
Tomato,
Parsley, Basil |
|
| Beans
|
Most Vegetables & Herbs |
|
| Beans,
Bush |
Irish
Potato, Cucumber, Corn, Strawberry, Celery, Summer Savory |
Onion
|
| Beans,
Pole |
Corn,
Summer Savory, Radish |
Onion,
Beets, Kohlrabi, Sunflower |
| Cabbage
Family |
Aromatic
Herbs, Celery, Beets, Onion Family, Chamomile, Spinach, Chard
|
Dill,
Strawberries, Pole Beans, Tomato |
| Carrots
|
English
Pea, Lettuce, Rosemary, Onion Family, Sage, Tomato |
Dill |
| Celery
|
Onion
& Cabbage Families, Tomato, Bush Beans, Nasturtium |
|
| Corn
|
Irish
Potato, Beans, English Pea, Pumpkin, Cucumber, Squash |
Tomato |
| Cucumber
|
Beans,
Corn, English Pea, Sunflowers, Radish |
Irish
Potato, Aromatic Herbs |
| Eggplant
|
Beans,
Marigold |
|
| Lettuce
|
Carrot,
Radish, Strawberry, Cucumber |
|
| Onion
Family |
Beets,
Carrot, Lettuce, Cabbage Family, Summer Savory |
Beans,
English Peas |
| Parsley
|
Tomato,
Asparagus |
|
| Pea,
English |
Carrots,
Radish, Turnip, Cucumber, Corn, Beans |
Onion
Family, Gladiolus, Irish Potato |
| Potato,
Irish |
Beans,
Corn, Cabbage Family, Marigolds, Horseradish |
Pumpkin,
Squash, Tomato, Cucumber, Sunflower |
| Pumpkins
|
Corn,
Marigold |
Irish
Potato |
| Radish
|
English
Pea, Nasturtium, Lettuce, Cucumber |
Hyssop
|
| Spinach
|
Strawberry,
Faba Bean |
|
| Squash
|
Nasturtium,
Corn, Marigold |
Irish
Potato |
| Tomato
|
Onion
Family, Nasturtium, Marigold, Asparagus, Carrot, Parsley, Cucumber
|
Irish
Potato, Fennel, Cabbage Family |
| Turnip
|
English
Pea |
Irish
Potato |
|
Ancient Companion Planting
For centuries, many Native American tribes throughout North America have cultivated corn, beans, and squash. The term “Three Sisters” was primarily used by the Iroquois who live in the Northeastern United States and Canada. These crops were considered to be special gifts from Great Spirit and were believed to be protected by the Three Sisters—spirits collectively called the De-o-ha-ko, meaning “our sustainers” or “those who support us”.
This ancient style of companion planting has played a key role in the survival of all people in North America. Grown together these crops are able to thrive and provide high-yield, high-quality crops with a minimal environmental impact. Corn, beans, and squash have a unique symbiotic relationship in a Native American garden. Corn offers a structure for the beans to climb. The beans, in turn, help to replenish the soil with nutrients. And the large leaves of squash and pumpkin vines provide living mulch that conserves water and provides weed control.
Corn
Corn is considered the most important of all Native American crops. Originating in South America and Mexico, corn was introduced during the Mississippian Period (600 A.D. to 1450 A.D.) to North American tribes via an intricate series of trade networks. Corn, beans, and squash combine to create a nearly perfect meal loaded with essential vitamins and minerals.
Beans
Beans provide a high-quality protein food source that combines well nutritionally with corn. Beans also play a valuable role in the Three Sisters garden. Through a symbiotic relationship with rhizobium bacteria, beans help to take nitrogen from the air and convert it into a usable form for next year's crop.
Squash
Growing low to the ground, squash and pumpkin serve as living mulch. The large leaves block out much of the sunlight, thus reducing weed seed germination. Allelopathy may be an additional factor in weed suppression. (Allelopathy refers to chemical secretions from a plant which have adverse effects on some weed species).
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