Question. I have set aside an area in my vegetable garden to try The Three Sisters system of growing corn, beans and squash. Do you have any suggestions as to what type of squash and beans to plant? (I've been told that I can use just about any type of pole bean (green beans or others) and just about any bush or non-vining cucumbers, squash or pumpkins to cover the ground. And are there recommended varieties for the corn?
---John in Edmond, OK
Answer. I learned quite a bit about The Three Sisters when we staged a major exhibit featuring Native American culture at the 1996 Philadelphia Flower Show back when I was the editor of ORGANIC GARDENING magazine in the 1990s. (Won Best of Show in our category for the third year in a row!) The three crops are part of an intricate Iroquois story about the world's beginning, springing out of the earth to feed and nurture the first Human Beings.
But you're a little misinformed about the specific nature of the crops in question. Although some corn and beans were almost certainly eaten fresh, the majority of the harvests of America's First Farmers were for winter storage. Thus, the corn was grown to be dried for grinding into cornmeal; same for the beans—they were selected for their ability to be dried and stored. Native Americans didn't know from cucumbers (which are not one of the sisters)—or even zucchini and other summer squash. Their squash would have been pumpkins and other winter squash, varieties that would store well, even improving in flavor over the winter. Think about it—there was plenty of fresh edible vegetation growing all around in the summer, but squirreling away lots of corn, beans and squash was essential for staying alive and healthy over the winter.
And the actual growing technique is a master class in space utilization. You'd plant varieties of flour corn whose stalks were especially sturdy, so they could handle the bean vines that would be tugging at them. Near those stalks, you'd plant 'pole' (climbing) beans that produced big, nutritious seeds, but whose vines weren't so heavy and aggressive that they'd start tugging the corn down to earth. Then, when those crops were up and growing, you'd plant pumpkins and other winter squash with really broad leaves around them—to shade the soil, conserve moisture and keep weed growth down. (The prickly squash leaves were also felt to help deter critters like deer and raccoon from going after the corn.)
To make the circle even more complete, the bean vines would be plowed back into the soil or buried in another area at the end of the season, so that the nitrogen-rich vines would decompose and provide some of the food for the next season's corn crop. Pretty smart! (If the correct bacteria are present in the soil, "nitrogen-fixing" crops like peas and beans can pull nitrogen from the air and store it in their cells. Modern growers insure this great symbiotic relationship by purchasing a specific pea and bean inoculant and dusting their seeds with it before planting.)
I wouldn't advise trying this technique with regular sweet corn or string beans, as the ideal Three Sisters are not picked during the season. It's hard to imagine how you could get in there TO pick without stepping all over the poor squash vines; and the stalks of modern sweet corns just aren't strong enough to support vigorous bean vines.
But there's a lot of benefit to growing storage crops. Unlike sweet corn and string beans, which must be picked within a certain window of ripeness, drying corn and beans are left to fully mature and then dry on the plant before harvest—by which time the squash should also be fully ripe.
The advisers who guided our hand in selecting the crops for our Flower Show exhibit specifically recommended the white corns "Tuscadora", "Iroquois White" and "Cherokee White"; the large, yellow-kernelled "Hickory King"; the dramatically blue-black kernelled "Black Iroquois" (aka "Black Mexican") and "Black Aztec"; and the multicolored "Rainbow Inca". (Note: Some flour corns—including the 'Black' ones listed here) can be harvested 'both ways'—the young ears make an acceptable sweet corn and the mature ears are good for drying—so, if there's a nice ear poking out where you can pick it when the silks are just beginning to dry, go ahead and sample it!)
Recommended beans included the beautiful speckled purple (when dried) "Scarlett Runner" (whose tubular red flowers attract lots of hummingbirds, and whose beans can be eaten fresh or dried); "Genuine Cornfield" (which will produce well even in Oklahoma-level heat); "Hopi Purple"; and the one that looked the nicest on dried-bean display in our Flower Show exhibit, "True Cranberry", an absolutely authentic Native American variety.
For squash, several sources recommended "Long Pie" (aka "Indian Pumpkin" and "Golden Oblong"), an especially long-keeping variety that was still being grown by Native American tribes back in 1996—it tastes great, but doesn't look much like a traditional pumpkin. But "Connecticut Field" does; in fact, it's the classic pumpkin shape and color! A well-known Native American heirloom, it's a great choice for completing the circle—the perfect shape and color for Halloween carving, it stores very well and has delicious flesh for pie-making and other baked good endeavors. And the cushaw type of bottle-shaped storage squashes are a well-documented traditional Native American choice—especially in the Southwest.
Planting styles vary greatly, but our experts agreed on a few things. In areas of normal rainfall, plant your systems in raised beds or built-up plots; but in dry areas like Arizona and Oklahoma, plant in slight depressions, with outer walls high enough to shield the young plants from dry winds. Multiple groups of three corn plants each is a common design, with just two pole bean plants per group (not per cornstalk!); more than that and the vines will overwhelm the corn. Go light on the squash as well; as people who have grown pumpkins and other squash know all too well, the vines grow aggressively and the leaves of just a few plants will cover a large area.
I'll add that this is a clear case for running drip lines over the area before planting. They'll make the most efficient use of irrigation water, and overhead watering would be begging for disease problems on all those squash leaves.
Harvest is easy; let the corn and beans stand until they're bone dry, and harvest the squash just before the first frost. And don't forget to bury the bean vines where you'll grow the Three Sisters the following year!