The Three Sisters are the three main agricultural crops of some Native American groups in North America, particularly in New England: squash, maize, and climbing beans (typically tepary beans or common beans).

In a technique known as companion planting, the three crops are planted close together:

  1. Flat-topped mounds of soil are built for each "cluster", about 30 cm (1 ft) high and 50 cm (20 in) wide.
  2. Several maize seeds are planted close together, in the very center of each mound.
  3. When the maize is 15 cm (6 inches) tall, beans and squash are planted around the maize, alternating between beans and squash.

The three crops benefit from each other:

  • The maize provides a structure for the beans to climb, eliminating the need for poles.
  • The beans provide the nitrogen to the soil that the other plants remove.
  • The squash spreads along the ground, monopolizing the sunlight to prevent weeds.
  • The squash also acts as a "living mulch," creating a microclimate to retain moisture in the soil.

In some parts of New England, a fish was often planted with the maize seeds, to act as additional fertilizer where the soil was poor.

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