Who are the three sisters?
The crops of corn, beans, and squash are known as the Three Sisters. For centuries these three crops have been the center of Native American agriculture and culinary traditions. It is for good reason as these three crops complement each other in the garden as well as nutritionally.
Corn provides tall stalks for the beans to climb so that they are not out-competed by sprawling squash vines. Beans provide nitrogen to fertilize the soil while also stabilizing the tall corn during heavy winds. Beans are nitrogen-fixers meaning they host rhizobia on their roots that can take nitrogen, a much needed plant nutrient, from the air and convert it into forms that can be absorbed by plant roots. The large leaves of squash plants shade the ground which helps retain soil moisture and prevent weeds.
These three crops are also at the center of culinary traditions and complement one another as well. A diet of corn, beans, and squash is complete and balanced. Corn provides carbohydrates and the dried beans are rich in protein and have amino acids absent from corn. Squash provides different vitamins and minerals than corn and beans. These three crops are also important because they can all be dried and used for food year round. These traits are less important today, but were important in the past which lead to their significance as the major cultivated foods.
The tradition of calling these crops the "Three Sisters" originated with the Haudenosaunee, pronounced Ho-deh-no-shaw-nee. Also known as Iroquois, Haudenosaunee live in regions around the Great Lake in the Northeastern United States and Canada. All three types of seeds are planted together in the same mound in the Haudenasaunee planting method. The elevated mound assists with drainage and avoids water logging of the plant roots which is important in this region that receives abundant rainfall in the summer.
In the Southwest, there are traditions of planting the Sisters together as well as in separate fields. In dry farmed areas like Hopi and portions of the Navajo Nation, the Sisters are planted in separate areas of fields with wide plant spacing to maximize limited water. In areas with adequate water the Sisters can be planted together in close proximity to get the companion planting benefits in the same cycle. Regardless of how they are planted, these three crops are some of the most important for Native American peoples of the Southwest in addition to other crops like tobacco, sunflowers, amaranth, and melons.
When and How to Plant
These crops are warm season plants and do not tolerate frost. Plant seeds for the Three Sisters outside with the spring, summer, or monsoon planting periods. Check with your local planting calendar to determine the best time for your area. One major concern for the Southern Southwest is the hot, dry heat of the early summer. Corn in particular does not tolerate high heat and low humidity during the period of tasseling. Therefore, plant before April 15 to ensure that the pollen released during the corn's tasseling period (30-70 days after planting depending upon variety) will occur before June/early July when it will be more likely to be sterile or infertile. Alternatively plant in mid-late July with the summer monsoon season and the corn will reach maturity when the temperatures drop a little and humidity rises.
We recommend directly planting all of these types of seeds as they will fare better than transplants. Direct planting of seeds leads to stronger root systems that are more adequately able to take up water and nutrients, resulting in more vigorous and healthy plants.
Planting the Three Sisters in the order of corn, beans, and squash will ensure that they will grow and mature together and will not grow at the expense of another Sister. Sister Corn should be planted first so that it can grow tall above the other crops. Plant seeds for Sister Bean 2-3 weeks later, or at least when the corn is a few inches tall. When the beans are sending out tendrils to climb the corn will be tall enough to support them. Plant Sister Squash seeds 1 week later after the beans have emerged. You don't want the large squash leaves to shade out young corn and bean seedlings before they have time to establish.
There are numerous configurations to Three Sisters Gardens. The main consideration is your space constraints. You will want to give individual plants enough space to thrive and have enough of each type of crop to facilitate pollination. Beans are self-pollinating so even only 1 plant will produce beans. They do get crowded growing up corn plants so expect slightly lower yields than if you grew them in their own plot. Squash require insects to pollinate the flowers so having several plants growing at the same time helps attract sufficient pollinators. Corn is wind-pollinated and while capable of self-pollinating you will have more success with more plants. It is best to have at least 10-20 corn plants to provide sufficient pollen availability but plant more if you have the space to increase your success.
The image below has some suggested layouts for a Three Sisters Garden and is also available in this PDF. Use your creativity and find what works with the space you have.
What Varieties to Plant
The corn should be a tall variety so the bean plants have plenty of room to climb and do not overcrowd the corn. Many Southwestern varieties of corn, such as Tohono O'odham 60-day and Hopi Sweet, are shorter plants that mature quickly. This is a beneficial trait selected to use less water, but not ideal for beans to climb. The bean variety should not be a bush bean but rather a climbing type also called pole beans. Non-vigorous climbers and bushy-pole types are best so that they do not take over the corn plants. Lima, runner, and common bean types do best. Teparies are not recommended for this type of planting. Corn and squash need more water than varieties of tepary beans so they do not grow well together. Traditional winter squash varieties can grow vines up to 15 feet long and therefore need adequate space to sprawl. Consider growing more compact summer squash varieties if you do not have much space such as a raised bed garden.
For corn, we recommend varieties like Dia de San Juan, an all purpose dent corn, or Flor del Rio, a tall popcorn that produces 2-4 ears per stalk. For beans, climbers like Tohono O'odham Vayos or Four Corners Gold work well. Recommended squash varieties depends upon your space. If you have a lot of space for the plants to sprawl consider winter squash varieties like Magdalena Big Cheese or Tarahumara Pumpkin. If you are planting in a raised bed or other restricted plot consider summer squash varieties like Dark Star Zucchini or Yellow Crookneck squash.
Photo courtesy of Pete Rodriguez
The Other Sisters
For some cultures, other crops are also important in traditional agriculture. For example, tobacco is equally sacred as Sisters Corn, Beans, and Squash for many indigenous cultures of the Southwest. Sunflowers and amaranth are considered other Sisters. They offer shade to the other Sisters during the heat of the afternoon, attract pollinators, and provide additional stalks for beans to climb. The edible seeds and amaranth greens contribute to a nutritionally balanced diet. Because they have a similar growing habitat, other cucurbits like watermelon and gourds can be substituted for the squash. The long, sprawling vines will shade the ground in a similar way to squash. Consider growing some of these other crops in place of or in addition to corn, beans, or squash depending upon what you like to eat and enjoy growing.