What is a Three Sisters garden?
A Three Sisters garden grows corn, climbing beans and squash together on the same ground. The corn comes up first and becomes a living pole. The beans twine up the stalks. The squash spreads its big leaves across the soil, shading out weeds and holding in moisture. Three crops share one patch, each using a different layer of it.
The name comes from the Haudenosaunee, the Iroquois Confederacy of what is now New York State and southern Ontario, who speak of corn, beans and squash as three sisters that belong together and sustain the people. Many other Indigenous nations across North America grew the same three crops together, each with its own varieties, layouts and traditions. All three plants were domesticated in the Americas, corn from a wild grass in southern Mexico thousands of years ago, and in Mexico and Central America the related milpa system of mixed corn, bean and squash fields is still farmed today.
The Three Sisters are not a gardening trick that someone invented for a seed catalog. They were, and are, a food system carried by Indigenous farmers for generations, and many Haudenosaunee and other Native communities keep growing their own heirloom corn, bean and squash varieties. If you grow them in a backyard, it is worth learning about the people who developed the practice, and buying seed from Indigenous-led seed projects where you can.
How the layout works
The tool above draws a block of low, wide mounds, about 18 to 20 inches across. Each mound gets four corn plants in a small square near its center and, a few weeks later, four pole beans around them, one per stalk. Squash goes on its own hills in the gaps between corn mounds, in every other gap, so the vines have room to run without burying the corn.
We space the mounds 5 feet apart, center to center, which leaves room for a squash hill between every four mounds. Many guides use 3 to 4 feet; that works too if you train the squash vines outward as they grow. There is no single correct layout. Traditional plantings varied from place to place and from family to family.
Keep the corn in a block. Corn is pollinated by wind: pollen falls from the tassels onto the silks of nearby plants, and a single long row leaves many silks unpollinated, which gives you ears with missing kernels. Two mounds deep in each direction means at least four rows of corn, the minimum most extension guides recommend.
Planting order and timing
- Build the mounds a week or two before sowing. Rake the soil into low, flat-topped hills and work in compost. Raised soil warms faster in spring.
- Sow the corn after your last frost, once the soil is 60°F at planting depth. Sow six seeds per mound and thin to the four strongest.
- Sow the pole beans when the corn is about 6 inches tall, typically two to three weeks later. Beans sown at the same time as the corn can outgrow it and pull it over.
- Sow the squash about a week after the beans, four seeds per hill thinned to two. Squash planted too early can shade the young corn.
Your ZIP code gives you dates based on your average frost dates and when your area normally warms to 60°F. For every other crop in your garden, see the planting calendar.
What the research says
The Three Sisters are often described with big claims: that the beans feed the corn, that the combination out-yields everything else. The research is more nuanced, and worth knowing before you plant.
The best-known study is by Jane Mt. Pleasant of Cornell University, who grew corn, beans and squash in traditional Haudenosaunee-style plantings alongside each crop on its own. The Three Sisters plots produced more food energy and more protein per acre than any of the single crops (Food Yields and Nutrient Analyses of the Three Sisters, Jane Mt. Pleasant, Ethnobiology Letters 7(1), 2016). In other words, as a way to feed people from a fixed piece of land, the system works very well.
Washington State University Extension’s review of companion planting is more skeptical (Gardening with Companion Plants (EM128E), Linda Chalker-Scott, Washington State University Extension, 2023). Grown together, each crop typically yields less than it would alone, beans in particular, and there is little evidence for many of the soil and pest benefits that get repeated online. Beans do host nitrogen-fixing bacteria in their roots, but most of that nitrogen stays in the bean plant during the season and only becomes available to other plants as the residue breaks down. Your corn still needs feeding.
Both things can be true. Measured as total food from a small area, the Three Sisters do well. Measured as the biggest possible harvest of any one crop, separate plantings usually win. In our companion planting chart, corn with beans and corn with squash are graded as mixed evidence for that reason.
Practical tips
- Use pole beans, not bush beans. Bush beans don’t climb. Pick a moderately vigorous pole or runner bean; the most rampant ones can topple the corn.
- Choose tall, sturdy corn. Flint, flour and dent corns have the strong stalks that traditional plantings used. If you want sweet corn, choose a tall variety and accept that it may need a little support.
- Use winter squash or pumpkins. Their long vines cover the ground between mounds. Bushy zucchini types don’t run, and summer squash needs picking every day among prickly stems.
- Feed and water. Corn is a heavy feeder. Work compost into the mounds, water deeply once a week in dry spells and side-dress the corn when it is knee high.
- Mind your other crops. Keep the patch away from tomatoes: the corn earworm and the tomato fruitworm are the same insect.
- Rotate. Corn is a very heavy nitrogen feeder; follow it with legumes. Next year, put the patch somewhere new and give the old ground to lighter feeders.
Want to see the patch next to your other beds? The Open in the planner button above copies it into the garden planner, where you can add raised beds, check neighbors and print a plan. For a closer look at each crop, see the guides for sweet corn, pole beans, winter squash and pumpkins.