Have you ever wandered through the forest and wondered to yourself how all of the plants manage to thrive together? Forests possess an astonishing level of biodiversity, flourishing without the need for added fertilizers or irrigation. The key to their survival is due to an intricate web of symbiotic relationships between plants, fungi, animals, insects, trees and microorganisms. Through mutual support and interdependence these things work in harmony, supporting the functionality of the forest’s ecosystem and life cycle of its inhabitants. Examples such as nitrogen fixing bacteria, mutualistic interactions with insects and vast networks of fungal mycorrhizae highlight the remarkable  interdependence and interconnectedness that allow ecosystems to flourish.

What may surprise you is that we can encourage and employ similar relationships in our own gardens and farms. By incorporating these types of relationships, our gardens can become dynamic and diverse systems that require fewer fertilizers and less water, while providing us with more delicious food! When we begin to see our gardening space as an ecosystem, a space where plants and creatures relate, we take the steps towards a more abundant future.

One of the most effective, tried and true ways to encourage relationships between plants is companion planting. Companion planting is the practice of growing plants together strategically. It takes advantage of positive interactions such as shade, support, pest repellent qualities, and through the creation of beneficial habitats. Companion planting is sometimes described as polyculture, which just means simultaneous cultivation. 

Throughout history companion planting has been practiced by indigenous communities around the world. This relationship and understanding of the natural world is described as traditional ecological knowledge (TEK) as opposed to scientific ecological knowledge (SEK). According to Robin Wall Kimmerer, a professor of Environmental and Forest Biology and an enrolled member of Citizen Potawatomi Nation, “Traditional ecological knowledge is not restricted to the biology of subsistence activities but includes detailed observations of population ecology and species interactions, which arise from long-term association with a particular flora and fauna.” (1) Plainly speaking, when you get to know the plants and non-human people around you, you start to create an understanding of the relationships of those creatures, which will in turn inform your interactions with them. Observation, care and a knowing, loving relationship between you and the world around you.

One of the most well known companion planting methodologies is colloquially known as Three Sisters Intercropping. Which generally includes a variety of corn, a dry bean and a squash variety and can often include a sunflower as well. Three Sisters Intercropping was practiced mostly by Indigenous communities in the midwestern portion of the United States. It has undergone a resurgence in use due to Indigenous food sovereignty movements and seed rematriation (2).

Three Sisters Intercropping is fairly ingenious. If we look at the relationships between the three plants we can see that the structure or action of each plant is mutually beneficial. The corn offers both a trellis for the beans but also perhaps acts as a physical barrier for insects. Squash plants are an incredible ground cover and their spiky stems can be deterrents for mammal pests (3). Beans are nitrogen fixers. All plants require nitrogen for growth. Plants that fix nitrogen allow colonies of soil bacteria known as rhizobium to form on their roots. These bacteria  convert nitrogen from the air into a bioavailable version for plants.  Clover is another excellent example of a nitrogen fixer. In a scientific study of companion planting clover with orchard grass, there was observable increase in soil microbiology as well as patterns showing significant nitrogen fixation (4).

Intercropping is not only significant to Indigenous people in North America but also shows up in other places such as India. The Dongria Khat tribes in the Eastern Ghats in India have agrarian practices where they incorporate over 80 different crops in their interplantings. They do this by sowing seeds in correlation to their climate needs and cultivate varieties which can handle adverse weather such as drought (5). As climate change will have a huge impact on agricultural systems it is important for communities to start adapting and maintaining agricultural practices that are capable of withstanding climate change. 

Companion planting is an important aspect of modern market gardening  practices. Market gardens use bio-intensive methods like companion planting to maximize available growing space, maintain soil health and create microclimates to protect sensitive crops. Now a popular movement among farmers in the United States, market gardening also known as “French Intensive Gardening” was developed in France from the 1500s to late 1800’s (6).

Now that we have a brief understanding of the significance of companion planting, let’s talk about how to employ some of these techniques in your own garden. Determine what your goals may be. Do you want to make the most of your garden space? Do you have issues with water evaporation during the summer? Does your garden have a lot of unwanted insect pests? There are lots of ways you can use companion planting to deal with those issues.

As we talked about in our  blog post Planting for Pollinators, by growing a diversity of plants you can attract a wide array of insects to your garden. Some that will pollinate your plants, leading to fruit and others that are predator insects of unwanted garden pests. Borage, when planted near strawberries in a study done in the UK, attracted more pollinators to the strawberry flowers which resulted  in more uniform and abundant fruit production (7). Phacelia is another flower that is used as an insectary plant because it produces a huge amount of pollen. It has shown efficacy when grown near Brassicas to decrease aphids by increasing populations of one of their natural predators (8). Aromatic herbs are another excellent addition to your garden. For example, according to “Carrots Love Tomatoes” by Louise Riotte, Thyme is known to deter cabbage worms while Sage is helpful at repelling cabbage moths (9). Not to mention that both Sage and Thyme are delicious culinary herbs to have around.

If you are hoping to maximize the food that comes out of your garden you can try intercropping with multiple crops that do not interfere with the growth of one another. When you grow multiple vegetables together try to grow fast growing crops with slow growing crops like growing scallions (green onions) between rows of cabbages. In my garden I currently have a fast growing row of radishes planted between two rows of chicory. The radishes are ready to eat now just as the chicory is spreading out across the bed. Grow deep rooted vegetables like carrots with shallow rooted crops like Arugula.  I currently have deep rooted parsley plants interplanted with head lettuce. I love the way interplanting looks, it adds a really appealing visual quality to the garden. There are lots of different ways that you can incorporate polyculture into your vegetable productions.

In conclusion, companion planting offers a delightful and engaging approach to gardening. While researching suitable plant combinations is beneficial, it's important to remember that many companion planting discoveries have been made through hands-on experience and keen observation. Don't be afraid to experiment and see how different plants interact in your own garden. You may stumble upon a truly delightful relationship that enhances both the beauty and productivity of your green space. Enjoy the journey of exploring companion planting, and may your garden flourish with the enchanting relationship of plant companionship.

Happy Planting!

Taryn Hunter
Lead Seed Coordinator, Siskiyou Seeds

References

1. Robin Wall Kimmerer, Weaving Traditional Ecological Knowledge into Biological Education: A Call to Action, BioScience, Volume 52, Issue 5, May 2002, Pages 432–438, https://doi.org/10.1641/0006-3568(2002)052[0432:WTEKIB]2.0.CO;2

2. Kapayou, D.G., Herrighty, E.M., Hill, C.G. et al. Reuniting the Three Sisters: collaborative science with Native growers to improve soil and community health. Agric Hum Values 40, 65–82 (2023). https://doi.org/10.1007/s10460-022-10336-z

3. Kuepper, George and Mardi Dodson. 2001. Companion Planting: Basic Concepts and Resources. ATTRA. Accessed at: <https://attra.ncat.org/attra-pub/summaries/summary.php?pub=72>

4. Chen L, Li D, Shao Y, Adni J, Wang H, Liu Y and Zhang Y (2020) ComparativeAnalysis of Soil Microbiome Profiles in the Companion Planting of WhiteClover and Orchard Grass Using 16SrRNA Gene Sequencing Data.Front. Plant Sci. 11:538311. doi: 10.3389/fpls.2020.538311

5. Aich A, Dey D, Roy A (2022) Climate change resilient agricultural practices: A learning experience from indigenous communities over India. PLOS Sustain Transform 1(7): e0000022. https://doi.org/10.1371/journal.pstr.0000022

6. Orin, M. (2007). For the gardener. Https:/Agroecology.Ucsc.Edu/Documents/for-the-Gardener/French_Intensive.Pdf. Retrieved from https://agroecology.ucsc.edu/documents/for-the-gardener/French_Intensive.pdf.

7. Griffiths-Lee, J., Nicholls, E. and Goulson, D. (2020), Companion planting to attract pollinators increases the yield and quality of strawberry fruit in gardens and allotments. Ecol Entomol, 45: 1025-1034. https://doi.org/10.1111/een.12880

8. Parker, J.E. & Snyder, William & Hamilton, G.C. & Rodriguez-Saona, Cesar. (2013). Companion planting and insect pest control. Weed and Pest Control - Conventional and New Challenges. 1-30.

9. Riotte, L. (1998). Carrots Love Tomatoes. Storey Publishing.

Coté, C. (2016). “Indigenizing” Food Sovereignty. Revitalizing Indigenous Food Practices and Ecological Knowledges in Canada and the United States. Humanities, 5(3), 57. MDPI AG. Retrieved from http://dx.doi.org/10.3390/h5030057

Written by Taryn Hunter