Companion planting is planting plants together that will aid in the growth of both species, repel pests and help control the weed population. It is a great addition to the many other practices used in organic gardening. It is practical and can be beneficial to both the plants and the soil. Companion planting is one way to be better stewards of our gardens too!
Protecting and Repelling
When using companion planting, understand that the benefits may or may not act quickly. For example, when using marigolds to help control “nematodes,” they need to be grown over for at least one season. Also in this situation more is better, as their protective properties are cumulative in nature. Likewise some companions planted together will diminish each other’s natural repellant qualities; you may want to vary these companions season by season.
A beneficial companionship is that of roses and garlic. Growing garlic between your rose bushes will protect the bushes against black spot. You can also puree garlic cloves in your blender with a quart of water and a tablespoon of oil and strain to spray on the flowers and foliage of plants to discourage insects and many of the blights that can be found on other flowers and vegetables.
Repellant and attracting qualities come from smell, and the root and leaf secretions of plants. For example the carrot fly plagues carrots while onion flies and leek moths afflict leeks. But planted together, the smell and secretions from the carrots repel the onion flies and the leek moths, and the leeks repel the carrot flies. Both grow up together healthier than they would if they were grown separately. It is similar when you grow kohlrabi or radishes with your lettuce – different pests, same effects.
Accumulating or “Fixing” Plants
There are also plants that are accumulating (or fixing) plants. These have the ability to collect trace minerals from the soil and retain them in their fibers. Many accumulators are plants that are usually considered weeds, but they are useful for adding to our compost piles, used as ‘green manures,’ or mulches. However, in order to be useful to our gardens they must be decomposed first.
Symbiotic Growing Partners
There are also those plants that grow well because of their relationship of soil depth, plant height and other aspects of their stature. A good example of this partnership is what the Native Americans taught our Pilgrim forefathers, that is, the legend of the “Three Sisters.” The three sisters are corn, beans, and pumpkins or squashes. The Native Americans would put a dead fish, three bean seeds, three corn seeds, and three squash seeds in the same hole. The fish would fertilize the plants.
Legend has it that as they dropped each seed in the hole, they would say for each group of seeds: “One for brother bird, one for brother squirrel, and one for the tribe.” This is why they planted three of each type of plant in each hole. The corn would grow tall like a pole, the beans would climb the stalk, and the squash would provide a living mulch to keep the ground cool and protect the young plants as they grow up.
Fruit and Nut Orchards
In the orchard we can easily see that this is a different type of plant community, yet it can benefit from companion planting. In small spaces we may be tempted to plant only one of any given type of fruit or nut tree. This would be an error. Fruit and nut trees must be planted in tandem to be pollinated properly. Planting one fruit or nut tree by itself will cause it to have beautiful blooms, but no fruit. As the old saying goes, “It takes two to tango,” or to pollinate for that matter. You can also under-plant your orchard with colorful, shade-tolerant flowers to attract more insects and birds to help in the pollination process.
Also you never want to plant a young tree in the same place where a tree of the same type died, because the root and leaf secretions of the dead tree will poison the new tree. For example, if there was an old apple tree that died in the orchard, the farmer would not want to plant a new apple tree in the same hole. However if he planted a cherry tree in the hole where he removed the dead apple tree, it would flourish, as the nutrients left behind by the dead apple tree would feed the cherry tree instead of poisoning it.
Companion Plant Categories
- Flavor enhancement — some plants, especially herbs, may change the flavor of other plants around them in small but noticible ways.
- Hedged investment — multiple plants in the same space increase the odds of some yield being given, even if one category encounters catastrophic issues
- Increased level interaction — plants that grow different heights in the same space can provide ground cover or work as a trellis for other plants
- Nitrogen fixation — plants that add nitrogen to the ground, making it available to other plants
- Pest suppression — repelling pest insects, weeds, nematodes, or fungi
- Pollinator and predator recruitment — the use of plants that produce a lot of nectar and protein-rich pollen in a garden is a good way to recruit beneficial insects that control pests. Some adult insects are nectar or pollen feeders, while in the larvae predators of pest insects.
- Positive hosting — attracts good insects or other organisms which benefit plants, as with ladybugs or some “good nematodes”
- Protective shelter — one type of plant may serve as a wind break or shade for another
- Trap cropping — plants that attract pests away from others
- Pattern disruption — in a monoculture, pests spread from one plant to the next. This is interrupted by companion plants.1 
Below I have included links to three charts that I found helpful in Companion Planting.
Get creative, plant some companions and see what ‘Crops Up!’
Charts To Use In Companion Planting:
1  All information in this article was taken from:
Carrots Love Tomatoes, Louise Riotte, 1975 by Storey Communications
Roses Love Garlic, Louise Riotte, 1983 by Storey Communications