Year-Round Companion Planting for Organic, Pesticide-Free Gardening

Just as we understand in the animal kingdom how different, unrelated species will mutually benefit one another, whether intentionally or not, so too does the plant kingdom experience the same caliber of harmony and symbiosis (mutual benefit). Herbs, fruits, grains, vegetables, and ornamental flowers offer a wide variety of benefits to surrounding plants both above soil (pest control, disease, pollination, and physical support) while amending soil nutrition and tilth to deter soil-borne diseases, insects, and weeds, while boosting flavor and yields.

Also known as intercropping among professional growers and greenhouses, companion planting is the purposeful cultivation of mutually beneficial (symbiotic) plants grown immediately next to one another. These companion plants may be similar in size, shape, and taxonomy, or they may be very contrasting and seem to have nothing in common. But it is these differences that make for a healthier, organic, and less labor-intensive gardening season.


History of Companion Planting

For well over a thousand years, various methods of intercropping have been documented throughout the world that are still honored today. Most notably, as Americans, we’re familiar with the Native American agricultural tradition known as the “Three Sisters” method, in which corn, beans, and squash are grown in tandem––corn providing the tall support trellis for beans, while beans replenish the soil with nitrogen, and the low-growing squash cools and protects the roots of both the corn and squash. Chinese rice farmers have intercropped their rice fields with Mosquito Fern (azollo fern) because it keeps other plants from competing with the rice, transfers nitrogen back into the soil, while preventing mosquitoes from laying eggs in the field. Japanese growers traditionally intercrop with clover as a proven weed-suppressant, while East African farmers plant both Silverleaf desmodium and Elephant Grass to deter their seasonal pests. Companion plants are not universal and will need to be adjusted dependent on region, climate, and crop.


Cover Crops

One of the most well-known examples of companion planting is the seasonal cultivation of cover crops––legumes and grasses known to replenish the soil of depleted nitrogen. Cover crops, such as clover, fava bean, hairy vetch, and mustards, are generally grown alongside members of the nightshade, cucurbit, and brassica families, to provide nitrogen and nutrients during the growing season. However, many cover crop grains, such as buckwheat, rye, and alfalfa, are planted after the harvest and allowed to overwinter, eventually being turned back into the soil as organic “green manure”.


Culinary Herbs

Despite cover crops being the most well-known of modern companion plants, the most surprising may be traditional culinary herbs. Classic heirloom herbs are one of the best-kept secrets used by growers to deter pests, leafhoppers, and diseases from the garden. Natural oils secreted by aromatic herbs such as catnip, chives, pennyroyal, sage, and rosemary, are known to repel pests due to its, sometimes toxic, chemicals creating an inhospitable environment to many aphids, mites, thrips, and leafhoppers. These same culinary herbs, however, will attract those beneficial insects and pollinators required to keep the garden healthy and productive, while known to improve flavor of surrounding crops such as tomatoes, berries, peas, and root vegetables.


Wildflowers

Nearly synonymous with bees, butterflies, and other essential pollinators, wildflowers are truly one of the oldest and most successful companion crops ever. While there are several thousands of known wildflowers in just North America alone, wildflower seed mixes often feature varieties domesticated to specific regions to best attract the local insects and pollinators to the garden.


Ornamental Flowers

Despite being traditionally grown for showy aesthetics and simple home decor, common ornamental flowers such as nasturtium, calendula, marigold, petunia, and alyssum––to name a few––are proven garden companions known to deter several disease-carrying pests. Low-growing alyssum, for example, is known to provide protection for spider habitats keeping your garden free of harmful insects while marigolds emit a potent chemical into the soil called limonene which, once established, will repel whiteflies and aphids for multiple growing seasons. Larger-scale farms and home gardens will often plant an entire row of ornamentals and herbs between each row of summer vegetable crops.


Companion planting is not an exact science because there are so many variables when preparing the garden such as climate, region, soil health, and choice of crop to just name a few. If new to companion planting, try a fall cover crop in the garden this season. Whether growing a legume or grain, cover crops are quick to mature and certain to show the fastest return on investment in your future harvests.

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8 comments

  • jiraporm66 04:50 AM

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  • Robin 04:32 PM

    Excellent article. Now to address the complaining about not spelling out what the companion crops are, the article clearly stated that the companion crops are regional or more accurately zonal. Do your own homework for your area. Again, excellent article. Thanks

  • JoAnn Baku 03:19 PM

    My one bad experience, sunflowers and cucumbers did not do well. Beets and horseradish do well. Green beans and potatoes seem to like each other, planted in adjoining beds. My sisters experiment did not turn out as well as I expected.

  • Stephanie 03:02 PM

    I enjoyed the article! The only thing I noticed was that it says that culinary herbs can improve the flavor of surrounding crops and this isn’t a fully true but is a myth that persists for whatever reason. I would have loved to have seen some examples of good companions as well.

  • Holly Whiteside 02:51 PM

    I did enjoy your article and got something out of it, but I’m sorry, I don’t think I agree with your term definitions. I would say “3 Sisters” is not an example of intercropping, but is an example of companion planting. And there is another term, “plant guild” which is similar, but not quite the same either. In nature, some plants rather consistently grow together. I didn’t believe this until my husband and I were travelling and he pointed it out to me. Both of us have been to agricultural schools, but on different continents. In the United Kingdom, when you see brambles (any in the raspberry/blackberry family), you will also see burdock and nettle. He was warning me to look out for nettle whenever I saw a bramble. Cultivated or wild, everywhere we went for a month, this was true. This is an example of a plant guild that occurs naturally, but is also mimicked by gardeners. Each of these plants both takes and gives different nutrients to the soil that strongly complement each other. Permaculturists mimic these natural guilds, or sometimes, try to construct one using their own reasoning of nutrient and sunlight needs. Companion planting is very similar, but as the name implies, it is manmade. It is planted. It may or may not mimic as found in nature, but as it often contains cultivated species, it can’t always be found in nature. Three sisters is an excellent example of companion planting. Each of these plants is from a different plant family, so they do not tend to compete for nutrients or experience the same problems. Squash, for example, often gets powdery mildew, but less so when it is off the ground. But is this found in nature? Definitely not. 3 Sisters was a cultivation design only, that occurred sometime during the very long cultivation of corn as we know it today, from its beginning as a grass. Intercropping also has a clue to its meaning in its name. INTERcropping. It implies between, alternating, etc. This is most often found in row planting but can be found in “square foot” planting, too. Usually the intention is quite different and more about the growth rate of different plants, space requirements, or preventing weeds by filling in. It is possible to have something that is both interplanted and is a companion at the same time. Say, sticking garlic rows in between rows of kale, or growing clover in between rows of broccoli would be both companion planting and intercropped. Intercropping is handy when you are growing something that will need a lot of space but will take a long time to grow. For example, I sometimes intercrop radishes while onions are small, harvest them out when ready, and by then the onions need more space. In the mean time, the radishes helped keep the ground covered. But they don’t really help eachother, so I don’t consider that companion planting. Usually in intercropping you are pairing a fruit or leaf crop with a root crop, or something of that nature. It is a way of “packing it in,” covering the soil and keeping it moist, and getting more crop per square foot. Anyway, that’s only my opinion, but I see companion planting and intercropping as different strategies. Thank you for your article, I did enjoy it.

  • Ed Raduazo 02:24 PM

    If you want more information go to : https://www.google.com/search?source=univ&tbm=isch&q=companion+planting+chart&sa=X&ved=2ahUKEwjForn-7f_qAhXFknIEHbPKBDoQsAR6BAgKEAE&biw=1945&bih=1263&dpr=2#imgrc=9XzdGdIT6_wQiM Ed

  • GiGi 10:53 AM

    Good article. I plant a three sisters garden. Cirn, squash and green beans.

  • Will Covert 10:43 AM

    Great article however it would have been an excellent article had you included examples of plants that do well together in companion planting.

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