Companion planting involves growing multiple plant species together so they benefit each other. It can reduce the need for fertilizers and pesticides by using chemical, physical, and spatial interactions between plants. Chemically, some plants make nutrients available to neighbors or release chemicals that repel pests. Physically, tall plants can shade shorter ones and plant canopies can block birds and insects. Spatially, some plants attract pests away from others or their placement protects crops. Examples illustrate combinations like cucumbers with beans and tomatoes with eggplant that benefit each other.

1. Garden Clippings
Niagara College Greenhouse & Nursery Success Sheet No. 114
Companion Planting
Definition vine borer in finding the vines and the prickly
Companion planting is growing two or more vines discourage raccoons from getting to the
plant species together so they can benefit corn plants.
from each other. This can be used on any Physical: Tall sun-loving plants shade shorter
scale and is sometimes called polyculture. plants, protecting them from the sun and
Companion planting balances an ecosystem, drying winds. Plant canopies can also
allowing nature to do its job. discourage birds and insects.
Benefits Chemical. Some plants capture nutrients that
Companion planting can reduce the need for can be used by their neighbours, reducing the
chemical fertilizers and pesticides. It need to add fertilizers to your garden. Beans,
stimulates plant growth and increases crop peas and clover capture nitrogen from the air
harvests. It also can reduce your work and for their own use, but Rhizobium bacteria
increase your enjoyment of your garden. make it available to neighbouring plants such
as corn. This reduces the need for nitrogen
History
fertilizer.
Although the science behind companion
Some plants produce chemicals that repel
planting is relatively new, this technique has a
harmful pests without harming the beneficial
very long tradition. It is even mentioned in the
insects. For example, African marigolds
Bible. Cultures around the world practise
release thiopene, which repels nematodes,
companion planting in large-scale agriculture
making it a good companion for vegetables.
as cover crops and nurse crops for grains and
This reduces the need to use chemicals for
in home gardens. Before scientific explana-
insect control.
tions, a spiritual belief existed about growing
food. The North American tribes believed the Examples of Plant Combinations
Main Crop Good Companion Poor Companion
“Three Sisters” (beans, corn, and squash) Cucumber Beans, broccoli, Rue, sage
grew well together because they were a gift celery, peas, radish,
from the Great Spirit. lettuce
Tomatoes Egg plant, Potatoes
Factors asparagus, carrot,
Three factors influence beneficial plant cabbage, peas
Onions Beets, cabbage, Peas
associations: spatial, physical and chemical. carrots
Spatial: Some plants can be used as a decoy to Beans Cabbage, beets, Onions
carrots, corn,
attract pests away from the main crop. An tomatoes, squash
example is collard greens, which attract the Potatoes Beans, corn, lettuce, Apples, pumpkins,
diamondback moth away from cabbage. The radish tomatoes
spatial placement of plants can protect crops Companion planting benefits plants, garden-
and promote growth. ers, farmers, the economy and the environ-
For example, corn, pumpkin and squash ment around the world.
when planted together protect each other
because the corn canopy confuses the squash Susan Barbetti, Class of 2007
Niagara College Greenhouse & Nursery
Niagara-on-the-Lake Campus, 135 Taylor Road, Niagara-on-the-Lake, ON L0S 1J0
phone: (905) 641-2252, ext. 4464; fax: (905) 988-4309; e-mail: jthomson@niagaracollege.ca
Website: http://www.niagaracollegegreenhouse.com