I’d like to talk about the Three Sisters. No, not the play written by Russian playwright Anton Chekhov, and not the three mountain peaks near Canmore, Alberta , Canada. I am talking about Three Sisters Agriculture used by Native Americans; corn, beans and squash.
If you have read anything about companion planting you will have come across a description of the Three Sisters as one of the best examples of companion planting that works. But have you ever seen any data to show that this system works? Did the Native Americans actually use this system?
The Three Sisters are the corner stone of the companion planting movement and if it is all a myth, is there any validity to the whole idea?
Companion Planting – The Three Sisters
What is it? Seems like a simple question, but as you read this post you will realize that it is not as clear cut as you might think.
This system is normally presented in the following way. It is an agricultural practice where corn, beans and squash are grown together. The bean benefits by climbing up the corn. The corn benefits by having the squash shade the ground, preserving moisture and keeping the roots cool. Both the squash and corn get fertilized by the bean which is a legume that fixes nitrogen from the air.
What a beautiful system – if it works. And that is an issue. Everyone talks about it as if it works, but almost no one checks the facts – except for Garden Myths.
Did Native Americans Use Three Sisters Agriculture?
You might think this is not an important question, but it is. You see, many authors use the fact that Native Americans used the system to validate the system. If they used it, it must work. There is of course no logic to this reasoning.
I am no historian, but numerous online reports say that Native Americans did use the Three Sisters. For example, “Jacques Cartier in his voyages up the St. Lawrence in 1534–1535 detailed the cultivation of the Three Sisters in fields near present-day Montreal.” (ref 1)
But things are not as cut and dry as many would lead you to believe.
- Native Americans were not followers of companion planting. Instead they used the system “because it required less time and labor than planting the crops individually.” They did not use it to increase yield.
- The crops were planted in large mounds which significantly affects yield, something most modern day suggestions fail to include.
- Corn production is good as a three plant polyculture, but bean and squash yields are much lower. The three sisters polyculture was used when corn was the main target crop , but it was not used when the main goal was to produce beans or squash. Then the more productive monocultures were used.
Native Americans did use the system, but not because it was a very productive system (more on this below). They used it, some of the time, to make their job easier.
Milpa – Another Form of Three Sisters
The Maya peoples and other Mesoamerican people of Central America used a similar system called Milpa agricuture that produces maize, beans and squash. Crops are grown for 2 years and then the land is left fallow for 8 years to recover.
Which Corn, Beans and Squash Were Used?
We copy the Three Sisters system because it supposedly works, but which type of seed were used by Native Americans?
Most modern day examples of this system suggest that you plant sweet corn, green beans, and squash.
In reality Native Americans grew maize, dried kidney beans and usually pumpkin.
The varieties of plants used by Native Americans was very different from the seeds grown today. Even if the historical companion planting system works, there is no reason to conclude that today’s seeds will also work.
Issues With The Three Sisters
The logic used to explain why the Three Sisters works is flawed.
Beans Produce Nitrogen
It is true that legumes fix nitrogen from the air, but almost none of the fixed nitrogen enters the soil around the bean plant. It is all used by the bean to grow and produce seeds.
When you harvest the beans, especially dry beans, there is very little nitrogen left in the plant. So even if the plant is dug into the soil, it does not add much nitrogen to the soil.
The corn does not get nitrogen from the bean plant next to it.
Squash Reduces Soil Evaporation
This statement is true because the large leaves shade the soil. But you have to remember that the squash and beans also use water from the soil. So they compete with the corn for water. Wouldn’t a wood chip mulch around the corn work better?
Three Sisters and Square Foot Gardening
I found numerous discussions about using the Three Sisters method in square foot gardening and in raised beds. Some of this is nonsense. Imagine growing all three crops in a 4 x4 ft raised bed? Some people are trying to do this.
Others recognize that you need more space and talk about 10 x 10 ft beds or 4 x 12 ft beds. That might be large enough, but consider the fact that the Three Sisters method used mounds of soil. In effect it is a raised bed without the side walls. The side walls of today’s raised bed really don’t provide any benefit in such large beds, except maybe aesthetics.
Does Three Sisters Agriculture Work?
The system obviously works because it has been used for several hundred years, but it is important to define what we mean by “works”. If works is defined as producing a crop, then we can easily conclude it “works”.
However, in order for this to be a good companion planting system it must produce more food as a polyculture, then the individual plants would produce as a monocultures. Growing these crops is all about growing food. If it does not produce more food, then it is not a good companion planting system.
Jane Mt.Pleasant has looked into the food produced by Native Americans using Three Sisters and concludes that, “This polyculture cropping system yielded more food and supported more people per hectare compared to monocultures of the individual crops.” It certainly seemed to work for them, but keep in mind that this conclusion is based on a lot of historical data, some of which is extrapolated which makes it difficult to reach firm conclusions.
There is limited scientific testing of the Three Sisters system in modern agriculture. One study that compared growing just corn to corn plus southern peas, showed an increase in yield when the two crops were grown together.
A feasability study to see if corn monocultures can be converted to Three Sisters polycultures in the Midwestern United States concluded that it would produce less yield, mostly due to the type of soil in this region. This research used mathematical modeling and not actual plantings.
A Master of Science Thesis tried growing the crops in Wisconsin, in two different areas. The study was only carried out for one year which limits its value. It used heirloom varieties, rather than modern day hybrids. This study concluded that:
- There was no difference in yield per plant between monoculture and polyculture.
- Calories per acre were greater in Three Sisters treatment than in monoculture for one of the sites, but not for the second site.
What does all this mean. From the limited amount of scientific studies we really can’t reach any firm conclusion. It is possible that the Three Sisters perform better than monocultures in some situations, but probably not in all situations. There seems to be no study looking at modern day hybrids so we don’t know if they work. The fact that it was used historically does not provide evidence that the Three Sister polyculture outperforms monocultures.
The current scientific evidence is not very strong to support the use of the Three Sisters. There is certainly no evidence, that I have found, that supports using it as the poster child for companion planting.
If you do use this method, it is important to use the hill method, which is quite different than the way most people arrange their crops. Details for this can be found in reference 1.
Just For Fun
You might be interested in Three Sisters, other than the one discussed here.
References:
- http://ojs.ethnobiology.org/index.php/ebl/article/view/721/413
- Developing an Effective Southernpea and Sweet corn Intercrop system; http://horttech.ashspublications.org/content/3/2/178.short
- Feasibility of Converting a Corn Monoculture into a Three Sisters Polyculture: https://sites.tufts.edu/gis/files/2017/06/Polakoski_Grace_CEE187_2016.pdf
- An Evaluation of the Productivity of the Native American Three Sisters’ Agriculture system in Northern Wisconsin; https://epapers.uwsp.edu/thesis/2007/Martinez.pdf
- Image source for square foot gardening; https://kbsgarden.wordpress.com/three-sisters-square-foot-garden/
Very interested in companion growing and any other information I can gather to enable us to grow our own food!!!!!
Hi! The key factor people are missing is that water is heavy. 8 lbs per gallon. A 5 gallon bucket is 40 lbs.
I carried buckets of water to water fruit trees in the country where I didn’t have means to reach 8 acres of ground. If you have to carry it you become very motivated to reduce the places you have to haul to.
The mounds are the important part. They concentrate the arable soil and soil dykes hold the water. When you can’t use a sprinkler, you have to dump several gallons into the basin formed so it doesn’t run off.
The three plants have different growth habits and don’t compete for light. They spread mounds well apart from each other to allow sun to get to the squash.
I got this from: “Gardening When it Counts” by Steve Solomon, who did extensive experiments on minimal watering regimes for survival gardening. Including the three sisters model.
The three plants are on the same hill and they do compete for light. Corn is tall and shades everything under it.
I saw it done once. At our church garden, one person planted one plot 3 sisters, then grew them separately on another. The plants on the 3 sisters plot did fine, but were significantly smaller then the ones planted separately. That makes sense to me.
That is what Native American found as well.
This is an old thread but came up on a gardening website. I always find we tend to romanticize the “old ways” forgetting that food production was a very labor intensive, difficult procedure for much of history so the methods could have multiple purposes (ease of planting being one of them). Most of our ancestors simply were trying to survive and assure adequate stores to get through winters or droughts. I always wonder if we were pressed to produce all our own food without any reliance on outside sources, what would our gardens actually look like? I have a feeling the esoteric nuanced theories would quickly fade and practicality would direct how we proceed. Thanks for your thoughts. I love reading about history and gardening;).
A commenter wondered what Native American in her right mind would bury food (fish) when planting corn.
That would be a person who understood the concept of restorative reciprocity as taught by her indigenous people.
There are questions on this page that cannot be answered by the voices on this page.
If this really is a question you would like answered, I suggest reading Braiding Sweetgrass, by Robin Wall Kimmerer, a woman who is both an indigenous person who has gardened using and understanding this method, and is also a trained botanist, and noted professor of environmental plant science.
This inspired me to get back to planting again in my own personal garden, despite the cold weather. Love you for this.
Someone in the comments made mention of fish being buried when planting corn. I read somewhere that that was a myth also. What Native American in her right mind would bury food when planting corn?
The breathless excitement and rigid orthodoxy with which the “Three Sisters” stories are told always made me suspicious about their truth.
Then the more I learned about agriculture the less plausible it all sounded.
Thanks for doing the hard and uncomfortable work of setting the record straight.
Robert, Thank you for this information. I am a Master Gardener. We work with a group of Hispanic children; all citizens but many of their parents and grandparents are immigrants from Guatemala, Mexico and Honduras for the most part. We wanted to do the 3 sisters planting as a nod to their culture. Many of the families originally came from farming areas. You’ve raised many good points about present day varieties and what earlier civilizations would have planted. The director of the program we work with wants us to use fava beans because they are popular with the families. Any info on that? I think we would do several demonstration plantings but also do more monoculture planting. What type of squash might come closest to what Mayans might have planted? Thanks again.
The Mandan Indians of North Dakota also used the 3 sisters method and also put in a fish. A now retired professor from UND, Fred Schneider also studied them and their methods. Yes, they used dry beans.