The Three Sisters: Harmony of Crops in the Garden

The Three Sisters is an important intercropping method of gardening developed by farmers of Indigenous cultures, whereby three crops are planted together in a shared plot. The traditional players are corn, beans, and squash, and according to Iroquoi legend, they are the three inseparable “sisters” that feed the land, feed people, and give insight into how we should live.

Why does the Three Sisters method work?

Intercropping increases the productivity of individual plants through a process known as interspecific facilitation. Each species contributes something that promotes the growth, reproduction, or persistence of the others. In a nutshell, because the individual plant players (corn, beans, and squash) employ different strategies for gaining resources, they can divide and conquer the resources instead of competing for them. The three plants work together harmoniously like a family, nourishing and protecting each other with their unique and complementary strengths.

So here are the details:

• Corn gives vertical support for the beans to climb up;
• Beans help stabilize the corn and provide necessary nitrogen that fertilizes all the crops.
• Large squash leaves act as a natural weed suppressor, help maintain soil moisture, and thanks to their slight spikiness, discourage predators from munching on its sisters.

Below the surface, the root structure of each crop is also a finely tuned machine.

• Corn roots are shallow and take up the top layer,
• Bean roots travel deeper,
• Squash roots take residence in the empty spaces.

This interlocking root system helps establish a symbiotic relationship with fungi and bacteria. The bacteria fix nitrogen into a form that plants can use, and fungi form mycorrhizae that improve water uptake and nitrogen and phosphate acquisition.

How do you plant the Three Sisters?

Just like all great relationships, timing is everything. Because these crops are warm season plants that detest frost, plan on installing these three crops in the spring when night temperatures are in the 50-degree range.

Here’s what to do:
Find a full sunspot and mound your soil about 4 inches high to help with drainage and soil warmth. You will be directly planting all three types of seeds together in the same mound but not at the same time.
(Directly planting a seed will encourage a stronger root system, and the plant won’t have to deal with transplant trauma.)

Plant in this order: corn, beans, then squash.

1. Plant 4 corn seeds first, 6 inches apart, so it can grow above the other sisters (make sure you get a tall variety).
2. Next, plant 4 beans 3 inches from the corn, 2 to 3 weeks later (or when the corn is a few inches tall). Good options are pole beans or runner beans (not bush beans).
3. Once the beans send out climbing tendrils (approximately 1 week later), plant 3 squash seeds 4 inches apart at the edge of the mound.
   Pumpkin, Butternut, winter squash, or other vine-growing types work well.
   (The reason you plant the squash last is that you don’t want the large squash leaves shading out your baby corn and beans before they grow up a bit.)

Regarding spacing, make sure each plant has ample room to grow and not be crowded, which could make them susceptible to pests and diseases. Also important is to plant enough of each crop for proper cross-pollination.

• This is especially crucial for squash plants, which need the help of insects to pollinate their flowers,
• And for corn, which appreciates a family of fellow corn.

The other alternative is to plant all this in several rows, instead of a mound. A 10 x 10-foot square is the minimum size to ensure proper corn pollination.

Any other ‘sisters’ you can plant?

While the traditional sisters are corn, beans, and squash, you can substitute tall sunflowers, watermelons, zucchini, and amaranth, for example. The important thing to remember is incorporating plants that work in harmony, that complement and help each other to become the best (and tastiest) they can be.