The Three Sisters companion planting method for growing maize (corn), beans, and squash was developed and used by Native Americans over a thousand years ago as a beneficial way to grow their three main agricultural crops together. They used variations on the approach throughout North America, with regional variations used to adapt to local growing conditions.
A benefit of this approach, besides efficient use of growing space, is that the squash provides a living mulch that covers the ground and helps to control weeds and conserve moisture. The corn provides a trellis for the beans, and the beans provide nutrients by fixing nitrogen in the soil. An additional benefit of the squash is that it may help deter raccoons, as they reportedly don’t like the prickliness of the squash vines scratching their sensitive feet and legs.
How to Choose Corn, Bean, and Squash Varieties for the Three Sisters
Start with what you like best when choosing your seed varieties for companion planting! I like popcorn, shell beans (for dried beans), and winter squash, but this is a matter of taste, not growing requirements.
Ideally, you want a taller variety of corn, a shorter variety of climbing bean, and a vining and not too bushy squash.
Sister Corn Varieties
Traditionally, grain corn was grown in the three sisters garden, but nowadays sweet corn is also used. Plant any type of corn you like but be careful to choose varieties that grow to tall enough to support the beans. Some dwarf corn varieties grow to only three or four feet high. You do not want to plant these with pole bean varieties such as Scarlet Runner that grow to ten feet long!
Sister Bean Varieties
Any climbing bean will do well, so long as it does not grow too long for the cornstalk. Climbing beans are also known as pole beans and runner beans. One consideration is how often you want to harvest your beans. Select varieties that are best for eating as green beans if you don’t mind regularly making your way through the squash vines to pick the fresh bean pods as they ripen. Dry or dried beans–also called shell beans–are left on the vine until the pod has completely matured and dried. Dry beans are usually harvested in the fall, around or after first frost.
Sister Squash Varieties
Pumpkins and winter squashes work best for the three sisters garden method as the vines spread out to cover the ground. Summer squash grows in bushes but may work if you space the plants to approximate the spread and groundcover of a vining variety.
Planting and Growing a Three Sisters Garden
Before I start, note that there is no single right way to arrange your three sisters. Use a layout that works for your own garden and climate.
Prepare your site by building a mound that is four to five feet wide and about a foot high. If you are building more than one mound, space the mounds at least five feed apart apart to allow room for the squash vines to spread. Ideally you will want to add well broken-down compost, to make the soil as rich as possible.
After all danger of frost is past, plant the seeds of corn ten inches apart and an inch deep in a circle. For a four foot mound, plant them in a two foot wide circle. For a mound that is five feet wide, make the circle three feet across. This comes to either eight or eleven plants respectively.
The corn must be planted densely, to enable good fertilization. Plant only one variety of corn in each mound. Once the corn is six inches tall, plant four bean seeds around each corn stalk, spacing them evenly. A week later, plant the squash seeds around the perimeter of the mound. Plant the same number of squash seeds as you planted corn. Do not plant the corn, beans, and squash all at the same time: the corn needs to get a head start, otherwise the fast-growing squash and beans will compete, and the beans will smother the corn.
The Fourth Sister
The fourth sister (that no-one talks about) is the flower for pollinators. Good choices include sunflowers and bee balm.
You can include dwarf sunflower varieties interplanted with the squash or you can substitute sunflowers for one or two of the corn plants in your hill.
Variations and Substitutions
Giant sunflowers make a great alternative to corn.
Peas can be substituted for beans or grown along with the beans.
Instead of pumpkins or winter squash, try watermelons, gourds, or any other vining member of the Cucurbitaceae family, as they share the same spreading and leafy growth habit. Cucumbers can also be substituted, but they may not be as productive when grown as one of the three sisters. This is because vining cucumbers grow and produce best when trellised.