We should preface this article by saying that we are mere amateurs on the topic of growing the Three Sisters (corn, beans, and squash). While a university student, I read everything I could find in the university library that seemed likely to include details on how to grow these crops together. Then our family started experimenting with them, and learning (again) that books can only get you so far. We have now grown various combinations of the Three Sisters for several years. Each year we alter things slightly, trying to improve on spacing or varieties to get the partnership to work better, and it works reasonably well now; but we would definitely not say that we have it all figured out. However, we hope that some of what we have learned can be helpful to others, so….
These notes are broken down into sections that proceed through the year, from planning the garden to enjoying the harvest.
Selecting Varieties
The Three Sisters were traditionally meant as winter staple crops; the varieties of corn (Zea mays), beans (Phaseolus vulgaris) and squash (Cucurbita spp., probably usually C. pepo in this area) were mostly grown for use as dry corn and dry beans, and either dried summer squash or winter squash. While you can grow green beans and sweet corn in a Three Sisters arrangement, it might not work as well, since most varieties won’t have been selected under those conditions (also, the patch can become a jungle late in the summer, which would make it harder to find and harvest green beans at regular intervals). Also, most Indigenous cultures seem to not have valued all three equally. Corn was always the main crop, with beans and squash being important, but definitely secondary, additions. Recent research has found that this will be reflected in yields, even if you select varieties well-suited to this growing arrangement: the corn will yield as much as it would grown as a monoculture, but beans and squash will yield considerably less. That is normal.
The Three Sisters were domesticated in Central America, and they all like hot weather. Depending on your location, you may need to be careful to pick varieties which will mature in your season length.
It is very important to choose varieties of corn and beans which are compatible: the beans must climb only as high as the corn can support. Do not plant a bean which grows ten-foot vines on a corn which only grows four feet tall, or you will not need raccoons to pull down your corn and ruin it; the beans will do it themselves. Choose varieties of beans which are described as pole or semi-runner beans, but be cautious of very vigorous varieties.
Planting
Timing
Officially, you should plant corn when the soil warms to 15ºC; I plant when the serviceberries (Amelanchier spp.) flower.
Beans need to be planted a while after the corn so that the corn has enough of a head start that the beans do not overwhelm it and pull it down when they start climbing. Wait until corn is 3-6” tall before planting beans (approximately two weeks here).
Some people say to wait to plant squash until you plant beans. That seems to be too late here; when I tried it in 2019 many squash did not mature. In 2020, I planted squash seeds at the same time as corn, and also transplanted squashes I had started indoors 3 weeks earlier. This worked better, and fruit matured, but they were still suppressed by the shade from the corn and less productive as a result.
In this climate (USDA Zone 4b/5a) it can be hard to get your crops to mature before frost. To accelerate things, you can pre-soak seed for corn, beans, and squash. Place seed in a dish with lots of water; leave 8 hours or overnight. In the morning drain the water, and rinse 2-3 times per day until seeds germinate. The advantage this gives you is faster emergence and greater cold hardiness when you plant. The disadvantage is that once you start seed soaking, you have limited time to plant. If you wait until the baby root has emerged from a seed, it is very hard to plant without damaging it, and the longer it grows the more vulnerable it is.
Arrangement
The way the Three Sisters are pollinated must be considered in planning how to plant. Corn is the determining factor here: it is usually cross-pollinated by wind, so it will produce better, fuller ears if grown in a larger block rather than in a row, though you can also hand-pollinate if this is not possible. Squash is insect-pollinated; a single squash plant can be pollinated by itself with insect or human help. Beans are self-pollinated.
I have used a hill system for my Three Sisters field (my ‘hills’ are no higher than the surrounding ground; they are just little circles of earth broken up with a hoe). Place hills of corn and beans centred 40” apart on a grid (assuming corn 6-8’ tall; shorter corn can be spaced closer together). Plant squash in separate hills between the rows of corn and bean hills, with one squash hill for every 4-8 corn hills.
In each hill, plant four corn seeds 1-1½” deep in a square with about a foot between seeds.
Once the corn has grown 3-6” tall, plant one bean seed 1” deep per corn plant in the hill between the corn plants.
Plant one or two transplants or two to four squash seeds a few inches apart and ½” deep in each squash hill. If planting seeds, thin to the best plant after a few weeks.
Maintenance
All sorts of varmints love to eat corn and baby bean plants. You may want to defend your planting. A friend told me he would never try to grow corn without an alarm system which “has four legs and barks”. I put electric fence around my field. Traditionally in many cultures, children or women would guard the field during the day, and men would guard it at night, more-or-less constantly from green corn time to harvest. I have read that the scratchy hairs on squash leaves will deter raccoons, so that if you have enough squash around your corn it will be safe. I believe that this rumour was started by raccoons which had learned to type. Never trust a raccoon. They are almost as smart and greedy as humans.
I prefer not to water my Three Sisters because of the scale of my planting. I don’t think they need it in average soil in an average year. You can if you want to, but stop watering when the corn and beans start drying down.
To control weeds, I hoe around the hills and pull weeds in the hills by hand.
Harvest and Storage
All three species are not frost-hardy. However, we often have a lot of corn and beans which aren’t yet dry when frost hits, and we find that long as they are pretty close to maturity, they seem to be fine even after it kills the leaves. Corn should be fairly dry before it is harvested. Husk it promptly after picking to prevent molding. It is dry enough to be stored when you cannot dent a kernel with your thumbnail. If you must harvest it before this stage, hang it up to dry indoors until it is fully dried. For drying, we find it helpful to braid the cobs.
Pole beans dry starting at the bottom of the plant and work their way to the top. You need to harvest the bottom ones before the top ones are mature, or they will begin to shatter before you get to them. Harvest dry beans when the pods are no longer leathery and the seeds get rattly inside. They are also dry enough to store when they cannot be dented with a thumbnail. If you need to harvest earlier, spread them out indoors still in their pods, and leave them to finish drying.
Dry beans are usually our priority when growing the Three Sisters, but beans can also be harvested earlier as “shelly” beans, or for “leather britches”, also called “hay beans”. Shelly beans have seed which is full sized, but not yet dry; shell the beans out of the pods and use them fresh like edamame (which are just soy beans harvested at the shelly stage), or like dry beans which have already been soaked and are ready for cooking. Leather britches are made with beans harvested around the same time as shelly beans, but while the pods are still green; only certain varieties work for them. They are dried, pod and all, by threading them on a string and hanging them up in a shady, airy place (in my case from a beam in the ceiling between our kitchen and dining room). When I want to eat them, I break them into short pieces. If I am thinking ahead, I pour boiling water over them and leave them sitting overnight to rehydrate; if not, we just add them to a soup (which is how we normally eat them) and let them simmer for a long time, until they are tender.
Pick winter squash with at least a 1” stub of stem. Cure indoors at room temperature for several weeks to a month, depending on the species. Store at room temperature.
Just like corn and beans, squash can also be harvested at the green stage. We usually call these summer squash or zucchini, and some varieties are specially selected for this. They can be eaten immediately at that stage, but some varieties (I recommend “Costata Romanesco” zucchini) can also be cut into ¼” slices, spitted on a dowel, and dried for winter food.
Cooking and Eating
Corn & Beans
Please see our article on using staple crops. There’s a section for legumes, which includes beans, and a section for corn.
Squash
Our favorite squashes are winter squash, which we eat roasted or cooked into various dishes, usually stir-fries and soups.
Dried squash is an interesting alternative, however, especially for those who become swamped with zucchini in the summer. Use it as a substitute for mushrooms in things like pizza sauce, or in soup. Like leather britches and dried nixtamal, it takes longer to cook than if it is fresh, so add it to a dish earlier than you would add it otherwise so that it has time to rehydrate.
Roasted squash seeds also make a delicious snack, if you have more than you want for planting next year.