December 7, 2023


"Knowledge is Power"

Time To Think About Planting

Companion planting is used by farmers and gardeners in both industrialized and developing countries for many reasons.

The Legend of the Three Sisters

The term “Three Sisters” emerged from the Iroquois creation myth. It was said that the Earth began when “Sky Woman” who lived in the upper world peered through a hole in the sky and fell through to an endless sea. The animals saw her coming, so they took the soil from the bottom of the sea and spread it onto the back of a giant turtle to provide a safe place for her to land. This “Turtle Island” is now
what we call North America.
Sky woman had become pregnant before she fell. When she landed, she gave birth to a daughter. When the daughter grew into a young woman, she also became pregnant (by the West wind). She died while giving birth to twin boys. Sky Woman buried her daughter in the “new earth.” From her grave grew three sacred plants—corn, beans, and squash. These
plants provided food for her sons, and later, for all of humanity. These special gifts ensured the survival of the Iroquois people.

Companion planting can be described as the establishment of two or more plant species in close proximity so that some cultural benefit (pest control, higher yield, etc.) is derived. The concept embraces a number of strategies that increase the biodiversity of agroecosystems. Generally, companion planting is thought of as a small-scale gardening practice.

Companion planting in gardening and agriculture is the planting of different crops in proximity for any of a number of different reasons, including pest control, pollination, providing habitat for beneficial insects, maximizing the use of space, and otherwise 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 forest gardens in Asia, and thousands of years ago in Mesoamerica.

The Scientific Foundations for

Companion Planting

While conventional agriculturalists and BD

practitioners may disagree over the validity of

sensitive crystallization research, there is

general agreement today on the validity of

several mechanisms that create beneficial plant


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 diamondback moth

away from the cabbage.

Symbiotic nitrogen fixation. Legumes.

such as peas, beans, and clover. have the

ability to fix atmospheric nitrogen for their

own use and for the benefit of neighboring

plants via a symbiotic relationship with Rhizo-

bium 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 thiophene, 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


Physical spatial interactions. 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

disorient 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, hoverflies,

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, 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


Security through diversity. A more

general mixing of various crops and varieties

provides a degree of security to the grower. If

pests or adverse conditions reduce or destroy a

single crop or cultivar, others remain to produce

some level of yield. Furthermore, the

simple mixing of cultivars, as demonstrated

with broccoli in University of California research,

can reduce aphid infestation in a crop. (ATTRA, 2007)

It doesn’t just matter what plants you grow, it also matters where you plant them. As author Jessica Walliser explains in her book, Plant Partners, gardens are “an ecosystem rather than a contrived environment,” and choosing to grow certain plants together can be the secret to gardening success. Companion planting works by pairing the right plants in garden beds to enhance the growth of one or both plants. But what are companion plants exactly?

Companion plants are plants that benefit each other in at least one way. Those benefits can include natural pest control, increased pollinator activity, improved plant and soil health, added shade and support, weed suppression, and better disease resistance.  

One of the most classic examples of companion planting is the Three Sisters, which was developed by Native American cultures centuries ago. In this companion plant pairing, corn, squash, and climbing beans are interplanted together to enhance the growth of each other. The corn provides support to the beans, the beans boost soil nutrients due to their nitrogen-fixing abilities, and the squash’s large leaves shade the soil to conserve moisture and block weeds.

The Three Sisters is just one example of companion planting, although there are many more.