Covering Ground with the Three Sisters

Reader Contribution by Pam Sherman
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Topsoil is eroding nationally at a furious rate, one third of arable land worldwide is desertified and more joining it daily…We gardeners can create regenerative mini ecosystems wherever we garden, helping to restore topsoil and healthy nutrient cycling, reduce irrigation, sequester carbon, and provide food for birds, bees, and other beneficials on land we tend. And in so doing, we can also feed ourselves fabulously.

A great place to start is covering the soil with the Three Sisters companion plant community and cousins. We can help ensure its success.

Why Keep the Soil Covered?

Especially in dry or otherwise challenged areas, keeping the soil covered moderates extremes of microbe-killing, water-sucking cold, heat,and drought. It breaks the force of raindrops, allowing them to percolate into the soil rather than smash its surface. It protects the soil from wind as well as water erosion. It keeps earthworms in the dark, just how they like it. It also helps keep unwanted weeds to a minimum.

Covered soil retains water better. Leaf drop, litter, and mulch contribute organic matter to the soil when it breaks down, starting immediately on the soil surface. “Each 1 percent increase in soil organic matter can result in as much as 25,000 gallons more soil water per acre.

Why cover the ground with plant communities like the Three Sisters rather than just single-species rows?

The synergy created by compatible diversity works in ways we are understanding more all the time as research continues. We do see the result, though: the more diverse the community of compatible plants covering the surface of the earth, the more diverse the community of beneficial microbes, the healthier our crops and land. Some commercial agricultural cover crop mixes now contain up to 60 to 70 different species.

How are microbes related to companionable ground cover?

The ground-covering sisters and cousins take the carbon they’ve drawn from the air and use it to make special delicious carbon compound sugars to attract the “right” microbes. The plants exude these sugars through their roots, different sugars attracting different types of beneficial microbes.

 “Slurping” up these sugars, the microbes now have the energy to go get the nutrients the plants need, which only microbes know how to release from rocks, pebbles, and soil organic matter (they use special enzymes for this). The microbes then bring the nutrients back to the plant…and get more yummy sugars in exchange. This is a healthy nutrient cycle.

Pests scratch their heads when faced with a diversity of plants standing arm in arm, growing well together. They are used to rows of monocultural, genetically identical plants to munch down—easy pickin’s. A variety of plants growing together is just too confusing and not worth the energy they’d have to invest in trying to figure out where the food is. And there is usually some factor somewhere in all that complexity to counter a pest or disease.

So dependent are we on these critters that some farmers refer to the microbes as the “herd beneath the soil” and to themselves as “microbe farmers.” Pesticides, fungicides, herbicides kill them off, of course–that’s what they are designed to do. Salt-heavy commercial fertilizers do, too. Simply keeping the soil covered with a diversity of healthy companion plants like our Three Sisters is the first key to success for the beneficial microbial community.

To keep the soil covered, how do you know what plants will do well with each other in a polyculture or companion planting situation? Some could inhibit each others’ growth. Fortunately, ancient traditions tell us that corn, beans, and squash grow well together. Which varieties?

The jury’s out. Seek out heritage and adapted varieties that are known to do well in your area or, if you are adventurous, set aside a few years to adapt varieties from outside your area. Ask indigenous and heritage Three Sisters gardeners in your region with similar growing conditions what they like and why. Just try. Many gardeners will want to plant the traditional pole beans to climb up the corn; some may prefer bush beans.

What about fourth sisters and cousins?

Again, traditions to the rescue. We are told that the Tewa people have grown Rocky Mountain Bee Plant (Cleome serrulata) as a fourth companion. This is a power plant in terms of edibility, medicine, color, and as a source for the black dye used in Tewa pottery. It grows widely in the U.S. And Canada. It’s up to you where exactly to put it in your garden plan. Experiment.

What about other plants mentioned in conjunction with the Three Sisters? Commonly mentioned are sunflowers, Bee balm/Wild bergamot (Mondarda fistulosa), and others.

Are there other crop or native pollinator plants you’d like to try adding? What works one place may not work in another or may not work at another time when the conditions are different. Ask your resource gardeners. If something’s not working, cut it back or take it out.

What about rototilling?

NRCS soil health advisers and regenerative ag farmers teach that tilling exposes and decimates soil. It should be used only to start the garden, to rip sod to create beds, and then not used again. Tilling destroys the humus homes the microbes have built for themselves, destroys water-holding humus, destroys the air and water channels and pores, favors the overgrowth of bacteria while decimating fungi. Fungi are hugely important in gathering and transporting nutrients to plants. And they sequester carbon in a big way; they themselves are breathtakingly long pipes made of carbon. For these reasons, no till is now becoming popular. Not tilling keeps the soil covered and allows topsoil to develop year after year.

What if you have an area of bad compaction? Don’t you need to till that?

Rather than till, plant deep root crops there to break it up, keeping the soil well covered and well fed with litter. (Deep-rooted weeds can also help break up deep compaction.) Poke holes in the soil as far down as you can, fill the holes with good compost to get the right microbes down there, and plunk a root crop seed right on top (daikon seem to be the poster child for this job, but any will do). They’ll start work on breaking up the compaction, allowing the soil to breathe. This way the soil stays covered and can build in health, while the compaction gets broken down naturally.

What if you are planting this year into bare soil rather than into cover crop litter?

Especially in dry and challenged areas, mulch as soon as possible. Don’t leave any bare patches, just leaving space for seeds and sprouts to get full sun. Keep the soil warm and cozy. Old legume and other plant parts from last season or last week make great mulch, chipped or shredded if you can. Use legume residue (roots and all other plant parts, including pods after shelling) around the corn; it’s a great nitrogen source when it breaks down. (Use this year’s Three Sisters crop residue as post-harvest mulch or compost it.) Soil-covering mulch and litter can come from any of last year’s crops, from weeds with reproducing parts removed, grass clippings, leaves, straw, and other sources. Add some compost or compost tea, aged manure or manure tea to help inoculate it with great soil microbes as a head start.

Growing the Three Sisters and cousins helps the soil stay covered, and we can assist them. This can help regenerate and maintain rich garden soil, leading to a beautiful, delicious, healthy Three Sisters ecosystem.

Pamela Sherman grows corn, beans, and squash with her husband in the high and dry Colorado Rockies and can be found online at Slow Food USA’s Three Sisters gardeners’ group calledPlant a Seed: Food for Change.


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