Native American farmers used broad squash and pumpkin leaves as living mulch to suppress weeds and conserve soil moisture in the Three Sisters planting method.

The Three Sisters technique is a sophisticated form of companion planting developed by indigenous peoples across North America, particularly the Iroquois and Cherokee nations, with roots reaching back at least 3,000 years. This polyculture system harnesses the unique biological strengths of each plant to maximize productivity and sustainability.The corn (Zea mays) serves as a sturdy vertical structure, eliminating the need for constructed supports. The beans (Phaseolus vulgaris) are nitrogen-fixers that form a symbiotic relationship with Rhizobium bacteria living in their root nodules. These bacteria convert atmospheric nitrogen into a form plants can absorb, effectively fertilizing the soil for both the corn and squash while reducing dependence on external fertilizers and maintaining soil fertility across multiple growing seasons.The squash (Cucurbita) functions as the living mulch, spreading across the ground with its expansive leaves. Research demonstrates that this ground cover reduces soil temperature by several degrees and significantly decreases evaporation rates. Additionally, the prickly hairs covering many squash vines act as a natural defense against small mammals and pest insects.Modern agricultural research from institutions like Cornell University has validated that this ancient method produces more calories and protein per acre than conventional monoculture farming. The system delivers a complete nutritional profile—carbohydrates, fiber, and amino acids—while preserving the local ecosystem. Today, the Three Sisters remains a cornerstone example of indigenous ecological knowledge and continues to inform sustainable agricultural practices in permaculture worldwide.