Three Sisters Garden: How to Plant Corn, Beans and Squash Together

The Three Sisters is a planting system developed by Indigenous peoples of the Americas and practiced for centuries, with many variations between nations; the version most often taught in the Northeast comes from the Haudenosaunee (Iroquois). It is the best-known example of companion planting, and one of the few where the benefits are easy to see: the plants share space by growing at different heights. This guide covers how it works, which varieties suit it, step-by-step mound planting from extension sources, timing, care and what to keep out of the patch.

How the three sisters help each other

• Corn grows tall and gives the pole beans something to climb.
• Pole beans climb the stalks, and as legumes they fix nitrogen from the air.
• Squash spreads big leaves over the soil, shading out weeds and slowing evaporation. Virginia Extension adds that prickly squash vines can discourage animals such as raccoons and rabbits.

Choosing varieties

• Corn: Cornell recommends dent, flint and flour corns, which are tall and sturdy, as especially suited to this system. Sweet corn works too, but pick a tall variety, since short stalks can be pulled over by vigorous beans.
• Beans: they must be pole (climbing) beans; bush beans will not climb. Cornell suggests heirlooms such as Genuine Cornfield or Scarlet Runner.
• Squash: traditionally a vining winter squash or pumpkin, such as Connecticut Field or Small Sugar pumpkins (Cornell). A bush zucchini fits a small bed but will not carpet the ground the same way.

When to plant

All three are warm-season crops. WVU Extension advises waiting until the soil has warmed to about 60°F; Cornell says corn can go in once nights are in the 50s°F, but no later than June in its region. In weeks from your last frost, that is around the frost date or a little after; our planting calendar shows the sweet corn, bean and squash windows for your frost date. The beans and squash follow the corn by a week or two, once the corn is up. For each crop on its own, see when to plant beans and when to plant zucchini and squash.

Step by step: the mound method

1. Prepare the soil.

   Pick a spot with 6 to 8 hours of direct sun and access to water, and work in compost (Cornell suggests a soil test first).

2. Build mounds.

   About 12 inches high and 18 inches to 3 feet across, spaced 3 to 4 feet apart in every direction. In dry areas, flatten the top and make a shallow dip to hold water (UGA and Cornell).

3. Plant the corn.

   Four to seven corn seeds about 6 inches apart in the center of each mound. Thin to three or four plants.

4. Add the beans.

   When the corn is about 4 to 6 inches tall, sow about six pole bean seeds in a circle roughly 6 inches out from the corn. Thin to three or four.

5. Add the squash.

   At about the same time, sow four squash or pumpkin seeds at the edge of the mound, about a foot out from the beans, and thin to one. In a larger patch you can instead give squash its own mounds between every few corn-and-bean mounds.

In a raised bed

No room for mounds? Our raised bed layouts include a 4×4 Three Sisters bed: corn in a block, pole beans sown at the corn once it is up, and squash spilling over the south edge. Corn is wind-pollinated, so plant it in a block of several short rows rather than a single line; a tiny planting may give patchy ears. The corn guide explains block planting.

Care through the season

• Water: about an inch a week from rain or irrigation (Cornell); keep pre-soaked seed moist at first.
• Hill and weed: weed gently and mound soil around the base of young corn stems for support.
• Feed the corn: side-dress with a high-nitrogen fertilizer, aged manure or fish emulsion when the corn is knee-high and again when silks appear (UGA and Cornell).
• Guide the vines: help wandering bean tendrils onto the stalks, and steer squash vines toward paths and edges so they do not smother the corn.
• Squash yield: once several fruits have set, pinching the runner tips sends more energy into them (UGA).

What to keep out of a Three Sisters patch

The sunflower one surprises people, because UGA and Cornell suggest sunflowers as a traditional addition around the edge of a Three Sisters garden, on the north side so they do not shade it. Virginia Extension, meanwhile, lists sunflower as incompatible with pole beans. If you add sunflowers, keep them as a separate border on the north edge, not among the bean-covered corn. More in what to plant with sunflowers, and every pair to separate is in the keep-apart chart.

Friendly extras around the edge

Virginia Extension lists marigolds and nasturtiums as squash companions, so either makes a cheerful border around the patch; see nasturtium companion plants and marigold companion planting. Cucumbers are also listed with corn and beans if you want a fourth vine, though they compete with the squash for ground.

Harvest

Pick sweet corn when the silks are brown and dry and the kernels are milky. Flint, dent and flour corns are usually left to dry on the stalk. Pick pole beans young for snap beans, or let pods dry on the vine for dry beans. Winter squash and pumpkins are ready when the rind is hard and the vine is drying; see pumpkins for curing. WVU Extension notes the bean and squash vines can go to the compost afterward.

Frequently asked questions

What are the three sisters in gardening?

Corn, pole beans and squash grown together. Corn supports the climbing beans, beans are a nitrogen-fixing legume, and squash leaves cover the soil and hold in moisture.

How far apart should Three Sisters mounds be?

Extension guides from Cornell and UGA suggest mounds about 12 inches high and 18 inches to 3 feet across, spaced 3 to 4 feet apart in every direction.

When do you plant the beans and squash?

After the corn is up, when it is about 4 to 6 inches tall, usually a week or two after sowing the corn.

Can I use bush beans or sweet corn?

Use pole beans; bush beans will not climb. Sweet corn can work, but Cornell recommends tall, sturdy dent, flint and flour corns, which hold the weight of the beans better.

Do I still need fertilizer in a Three Sisters garden?

Yes. Cornell notes most of the beans' fixed nitrogen is not available to the corn in the first year, and corn is a heavy feeder, so side-dress it when it is knee-high and again at silking.