Is companion planting as simple as looking at a companion chart for the home garden? Actually, it has a complex history! In ancient days, some farmers believed in growing similarly colored plants together. Others used astrological signs to govern their planting time.
Native American concepts
Many Native Americans tribes used companion gardening. The Massachusetts Wampanoag tribe’s “Three Sisters” garden—corn, beans, and squash—was also instrumental in helping English settlers survive. Corn provided needed support for pole beans, which helped “fix” nitrogen in the soil to benefit all the plants, while the leaves of the squash kept down weeds and preserved moisture. The tribe used an intensive gardening style without plowing or tilling, with fish as fertilizer for maize (corn). The sunflowers often planted outside the Three Sisters garden (why it wasn’t called the Three Sisters and One Brother garden escapes me!) made an alluring picture.
Modern day companion planting
Although home gardeners may consider companion planting a practice for small gardens, new terminology helps explain how plant relationships are applicable to large-scale farming. Dr Linda Chalker-Scott uses the term “plant associations” to refer to the natural relationships among plants. “Intercropping” and “polyculture” are agricultural methods using mutually beneficial species. Our scientific understanding of “plant associations” includes:
• Releasing nutrients helpful to other plants
Symbiotic nitrogen fixation is a plant association that provides many benefits. Legumes “fix” atmospheric nitrogen for themselves and their neighbors. This is especially helpful to plants that need nitrogen, i.e., corn and potatoes.
• Providing buffers against the elements to other seedlings
• Harboring beneficial insects
Justin Duncan, updating Kuepper and Dodson’s work, discusses trap cropping: Planting a less-valued crop susceptible to insect damage in a neighboring field, row, or even among plants can entice destructive bugs away from the more desired plant. For example, planting a row of collards to pull the diamond back moth away from cabbages. Push-pull trap cropping involves incorporating one plant to repel insects and another plant to attract beneficial insects to aid the main crop.
Plant associations can also aid with weed suppression; the growth of pumpkins and squash leaves tamp down weeds and retain moisture in the soil. Certain plant companions can also change the root zone environment for the better and/or reduce the risk of plant diseases.
No doubt about it, companion planting or plant associations can contribute to a healthy garden. So, go on out there and plant your potatoes next to the beans—the beans will fix the nitrogen for the potatoes which are heavy nitrogen feeders. Enjoy your own tasty vegetables and know that they have profited from their neighbors.
Article by Alison Perez, Extension Master GardenerSM Volunteer
For more information:
Companion Planting and Botanical Pesticides: Concepts and Resources, George Kuepper, Mardi Dodson, Justin Duncan https://attra.ncat.org/attra-pub/download.php?id=72
The Myth of Companion Plantings, Linda Chalker-Scott https://s3.wp.wsu.edu/uploads/sites/403/2015/03/companion-plantings.pdf