Considered gifts to mankind by tribes of the First Nations, corn, beans, and squash have been grown together for centuries in the Americas. Although the grouping is the subject of several legends, it's also an early and sophisticated variation on sustainable agriculture. The seeds of each type of vegetable, grown in single varieties, are easy to harvest and save from year to year. Corn provides a growing support for the beans, which in turn provide nitrogen for the corn and squash. The squash grow quickly, acting as a mulch against weeds. All three types of plant are heavy feeders, so grow this ancient combination in rich, well-drained soil and add a small handful of complete organic fertilizer beneath each planting site. This Three Sisters Mix Seeds collection contains Golden Bantam corn, Scarlet Runner Beans, and Red Kuri Squash.
Wait until the soil has warmed up in late spring. The soil should be consistently 18°C (65°F). Start by planting the corn seeds 30cm (12") apart in as close to a grid shape as possible. Sow the bean seeds outside the perimeter of this grid. Sow the squash seeds at the corners of the grid so they are also 30cm (12") from the nearest corn seed.
Otherwise, start all the seeds indoors 3-4 weeks before planting out, and aim for the same kind of spacing. It may look sparse at first, but these are fast growing plants.
These big plants will grow in almost any soil, but getting the cob to mature is another matter. The maturity of the ears (cobs) is not controlled by the size of the plant, nor by day-length, but by the accumulated heat the plant has had while it grew. They call this the “heat units”. Only temperatures above 50 F count after the last killing frost of spring. Temperatures above 50 F add up to create the heat units. Corn plants generally grow very tall, and will shade other vegetables. Some plants will benefit from this shade, such as lettuce, but heat-loving plants must be placed so that the corn does not shade them. This heavy-feeding plant also provides a stalk for plants such as Pole Beans. Follow along with this handy How to Grow Corn from seeds Guide and grow food.