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You are here: Home / Articles / A Permaculture Guide to Choosing Cover Crops

A Permaculture Guide to Choosing Cover Crops

April 20, 2016 By Toby Hemenway 8 Comments

One of my constant refrains is “Permaculture is a decision making tool for arriving at regenerative solutions.” Here I’m going to show how permaculture can help create strategies for deciding what cover crops to use. In permaculture, we’re always looking for potent leverage points, and soil-building is a big one. If we create fertile, water-absorbing, biology-rich soil, a lot of higher-level problems—things like insect damage, low nutrition, poor growth, and excess water use—all go away. And cover cropping, which is the use of specific plants to add organic matter and nutrients, is a great way to build soil. I use other methods, such as composting and nulching, but there’s something about having living roots in the soil that makes cover cropping extra effective. That thick network of roots is constantly exuding sugars and other microbe food, creating a life-rich rhizosphere that pumps nutrients into plants and builds a lush habitat for mycelium and other beneficial organisms.

I’m going to use cover cropping to illustrate how permaculture decision-making works. How do we design a cover cropping program? Good design has three major components: setting a goal, developing strategies, and choosing techniques. First, we already have our goal: We want to build our soil’s fertility, organic matter, and tilth. There are many strategies for reaching this goal. (A strategy is simply a plan, or, as management consultant Henry Mintzberg puts it in my favorite definition, a strategy is a pattern in a stream of decisions) Different strategies for soil building include composting, sheet mulching, chemical fertilizers, organic fertilizers, cover cropping, and several more. It may seem like those are techniques rather than strategies, but I think of them as strategies because there are so many different ways of doing each. Do any two people build a compost pile in the same way? And we have many different kinds of cover crops, and a host of ways to use them. That’s why I think of each of those as a strategy: Just because we’ve arrived at cover cropping as a way to build soil, we’re not done with making decisions. There’s a “lower” or more fine-grained level that we need to make some choices about. We need to choose the specific variety of cover crop, how and when we will plant, and how we will get that cover crop into the soil, such as by tilling, chop-and-drop, or harvesting and composting it. So we need to have some criteria in mind to help us make those decisions. That’s one of permaculture’s strong points: It gives us tools that remove a lot of uncertainty from making decisions. That lets us rest in the near-certainty that we’ve made appropriate choices.

To start that decision-making process, we first gather up information about cover crops—we make lists. The first obvious list to make is simply a compilation of all the varieties of cover crops that can grow in our conditions. A little Googling will get us there. One of my top sources of cover crop information is Peaceful Valley Farm Supply (https://www.groworganic.com). They ‘ve got a huge assortment. But a simply list of cover crop species doesn’t get us very far. We need to break it down into some categories, because we can’t just plant any old cover crop; every soil has specific needs and conditions. Fortuitously, the drop-down menu on cover crops at the above link has already done some category-making for us. They’ve divided cover crops into fall-planted or cool-season types, warm-season types, and year-round varieties. These categories give us a handy machete to begin chopping our way through the cover-crop thicket.

What other categories will be useful in choosing cover crops? Another big dividing line is between plants that fix nitrogen and those that don’t. Nitrogen-fixing cover crops are varieties that have a symbiotic relationship with specialized bacteria that can take gaseous nitrogen from the air, which plants can’t use, and transform it into nitrate, nitrite, or ammonia, which plants can take up as fertilizer. Non-nitrogen fixing cover crops are important too. They build biomass and add carbon to the soil, which feeds beneficial soil organisms, helps retain moisture, lightens and fluffs heavy soil and—oh, right—alleviates climate change by pumping carbon dioxide out of the air and storing the carbon in the soil. Most cover crop blends contain a mix of N-fixers and non-N-fixers.

A third division, near and dear to permaculturists, is that between annual and perennial cover crops. Annuals are great if we’re going to till in the cover crop or follow the cover crop with something else. But there’s a role for perennials, too, in paths or between rows of production crops, or as a constant biomass source. In a perfect world, all gardeners and farmers would be generating their own fertility on-site, not importing it from somewhere else that might be impoverished by the constant drain of organic matter. Ecological garden guru John Jeavons says that we should be dedicating roughly four to six times the area of our food garden to fertility crops to cover what we withdraw from harvesting. Before the fossil fuel era, most farms allotted more land for fertility production in the form of pasture for generating animal manure than they did for food production.

We could come up with other categories, such as soil preference (clay, silt, sand), frost hardiness, and so forth, but the three I’ve outlined above are the ones I use most often. Those categories create a two-by-two-by-two matrix or three-dimensional chart that really helps to zero in on the right choices. Let’s build that chart.

USDA Cover Crops

Here’s a table of over 100 useful cover crops, edited from a USDA list at http://plants.usda.gov/java/coverCrops?sort=comname

Click to download the table below as a PDF

Scientific Name Common Name Plant Family
Amaranthus caudatus foxtail amaranth Amaranthaceae – Amaranth family
Amaranthus cruentus red amaranth Amaranthaceae – Amaranth family
Amaranthus hybridus × hypochondriacus Plainsman amaranth Amaranthaceae – Amaranth family
Amaranthus hypochondriacus Prince-of-Wales feather Amaranthaceae – Amaranth family
Arachis glabrata rhizoma peanut Fabaceae – Pea family
Arachis hypogaea peanut Fabaceae – Pea family
Avena sativa common oat Poaceae – Grass family
Avena strigosa black oats Poaceae – Grass family
Beta vulgaris common beet Chenopodiaceae – Goosefoot family
Beta vulgaris ssp. cicla chard Chenopodiaceae – Goosefoot family
Brachiaria ramosa signalgrass Poaceae – Grass family
Brassica hirta white mustard Brassicaceae – Mustard family
Brassica juncea brown mustard Brassicaceae – Mustard family
Brassica napus var. napus rape Brassicaceae – Mustard family
Brassica napus var. pabularia Siberian kale Brassicaceae – Mustard family
Brassica nigra black mustard Brassicaceae – Mustard family
Brassica rapa var. rapa field mustard Brassicaceae – Mustard family
Bromus hordeaceus soft brome Poaceae – Grass family
Cajanus cajan pigeonpea Fabaceae – Pea family
Camelina sativa false flax Brassicaceae – Mustard family
Canavalia ensiformis jack bean Fabaceae – Pea family
Carthamus tinctorius safflower Asteraceae – Aster family
Chenopodium quinoa quinoa Chenopodiaceae – Goosefoot family
Cicer arietinum chick pea Fabaceae – Pea family
Cichorium intybus chicory Asteraceae – Aster family
Crotalaria juncea sunn hemp Fabaceae – Pea family
Cucurbita gourd Cucurbitaceae – Cucumber family
Cyamopsis tetragonoloba guar Fabaceae – Pea family
Daucus carota var. sativus carrot Apiaceae – Carrot family
Echinochloa crus-galli Barnyard grass Poaceae – Grass family
Elymus hoffmannii RS wheatgrass Poaceae – Grass family
Elymus trachycaulus slender wheatgrass Poaceae – Grass family
Eragrostis tef teff Poaceae – Grass family
Eruca vesicaria ssp. sativa rocketsalad Brassicaceae – Mustard family
Fagopyrum esculentum buckwheat Polygonaceae – Buckwheat family
Glycine max soybean Fabaceae – Pea family
Helianthus annuus common sunflower Asteraceae – Aster family
Hordeum barley Poaceae – Grass family
Hordeum pusillum little barley Poaceae – Grass family
Hordeum vulgare common barley Poaceae – Grass family
Indigofera hirsuta hairy indigo Fabaceae – Pea family
Lablab purpureus hyacinth bean Fabaceae – Pea family
Lathyrus sativus white pea Fabaceae – Pea family
Lathyrus sylvestris flat pea Fabaceae – Pea family
Lens culinaris lentil Fabaceae – Pea family
Lespedeza capitata roundhead lespedeza Fabaceae – Pea family
Linum usitatissimum common flax Linaceae – Flax family
Lolium perenne ssp. multiflorum Italian ryegrass Poaceae – Grass family
Lolium rigidum Wimmera ryegrass Poaceae – Grass family
Lolium temulentum Darnel ryegrass Poaceae – Grass family
Lotus corniculatus bird’s-foot trefoil Fabaceae – Pea family
Lotus tenuis narrowleaf trefoil Fabaceae – Pea family
Lupinus lupine Fabaceae – Pea family
Lupinus albus white lupine Fabaceae – Pea family
Lupinus angustifolius narrowleaf lupine Fabaceae – Pea family
Medicago littoralis water medick Fabaceae – Pea family
Medicago lupulina black medick Fabaceae – Pea family
Medicago polymorpha Bur clover Fabaceae – Pea family
Medicago rugosa gama medic Fabaceae – Pea family
Medicago sativa alfalfa Fabaceae – Pea family
Medicago scutellata snail medick Fabaceae – Pea family
Medicago truncatula Barrel clover Fabaceae – Pea family
Melilotus alba white sweet clover Fabaceae – Pea family
Melilotus officinalis sweetclover Fabaceae – Pea family
Mucuna pruriens velvet bean Fabaceae – Pea family
Onobrychis viciifolia sainfoin Fabaceae – Pea family
Panicum miliaceum proso millet Poaceae – Grass family
Pennisetum glaucum pearl millet Poaceae – Grass family
Phacelia tanacetifolia lacy phacelia Hydrophyllaceae – Waterleaf family
Pisum sativum garden pea Fabaceae – Pea family
Poa pratensis Kentucky bluegrass Poaceae – Grass family
Psathyrostachys juncea Russian wild rye Poaceae – Grass family
Puccinellia distans weeping alkaligrass Poaceae – Grass family
Puccinellia nuttalliana Nuttall’s alkaligrass Poaceae – Grass family
Raphanus sativus cultivated radish Brassicaceae – Mustard family
Secale cereale cereal rye Poaceae – Grass family
Sesbania bispinosa dunchi fiber Fabaceae – Pea family
Sesbania herbacea bigpod sesbania Fabaceae – Pea family
Sesbania sesban Egyptian river hemp Fabaceae – Pea family
Setaria italica foxtail millet Poaceae – Grass family
Sinapis alba white mustard Brassicaceae – Mustard family
Sorghum bicolor sorghum Poaceae – Grass family
Sorghum bicolor × S. bicolor var. sudanense Sudex (Sorghum-sudangrass) Poaceae – Grass family
Sorghum bicolor var. bicolor × bicolor var. sudanense Sudex Poaceae – Grass family
Spinacia oleracea spinach Chenopodiaceae – Goosefoot family
Thinopyrum intermedium intermediate wheatgrass Poaceae – Grass family
Thinopyrum ponticum tall wheatgrass Poaceae – Grass family
Trifolium alexandrinum Egyptian clover Fabaceae – Pea family
Trifolium ambiguum Kura clover Fabaceae – Pea family
Trifolium fragiferum strawberry clover Fabaceae – Pea family
Trifolium hirtum rose clover Fabaceae – Pea family
Trifolium hybridum alsike clover Fabaceae – Pea family
Trifolium incarnatum crimson clover Fabaceae – Pea family
Trifolium pratense red clover Fabaceae – Pea family
Trifolium repens white clover Fabaceae – Pea family
Trifolium subterraneum subterranean clover Fabaceae – Pea family
Trifolium vesiculosum arrowleaf clover Fabaceae – Pea family
Trigonella fenugreek Fabaceae – Pea family
Triticosecale rimpaui triticale Poaceae – Grass family
Triticum aestivum common wheat Poaceae – Grass family
Urochloa ramosa browntop millet Poaceae – Grass family
Vicia atropurpurea purple vetch Fabaceae – Pea family
Vicia benghalensis purple vetch Fabaceae – Pea family
Vicia faba fava bean Fabaceae – Pea family
Vicia grandiflora large yellow vetch Fabaceae – Pea family
Vicia sativa garden vetch Fabaceae – Pea family
Vicia villosa winter vetch Fabaceae – Pea family
Vigna radiata mung bean Fabaceae – Pea family
Vigna unguiculata cowpea Fabaceae – Pea family
Vulpia myuros annual fescue Poaceae – Grass family
Zea mays corn Poaceae – Grass family

Next we need to organize these by dividing them up into our matrix. We’ve got 3 categories and two choices in each category.

  • N or B: nitrogen-fixer or biomass accumulator;
  • W or C: warm season or cool season; and
  • A or P: annual or perennial.

Two choices in each of three categories makes eight possible combinations in our matrix, which I will label like this:

  • NCA (N-fixer, cool season, annual)
  • NCP (N-fixer, cool season, perennial)
  • NWA (N-fixer, warm season, annual)
  • NWP (N-fixer, warm season, perennial)
  • BCA (Biomass, cool season, annual)
  • BCP (Biomass, cool season, perennial)
  • BWA (Biomass, warm season, annual
  • BWP (Biomass, warm season, perennial).

We can organize those eight combinations in a matrix:

 

CubeFinal

And now we need to split our cover crop variety list into those eight categories. I’ve created a table, below, with the cover crops divided into annuals, perennials, N-fixers, and biomass plants, but having spent more time on this post than I intended to, I haven’t divided them into warm and cool weather crops. Sample cool weather cover crops are fava beans, winter wheat, and vetch. Warm weather cover crops include alfalfa, sudan grass, and buckwheat. Interested readers can use the catalog and tables from Peaceful Valley Farm Supply or other sources on the web to create the remaining categories. Or maybe I’ll get around to it someday.

Cover Crops By Function

Click to download the table below as a PDF

N- fixer, Annual N-Fixer, perennial Biomass, annual Biomass perennial
arrowleaf clover alfalfa annual fescue browntop millet
chick pea alsike clover barley chicory
cowpea bigpod sesbania black mustard Intermediate wheatgrass
crimson clover bird’s-foot trefoil black oats Italian ryegrass
Egyptian clover black medic buckwheat Kentucky bluegrass
Egyptian river hemp bur clover carrot Nuttall’s alkaligrass
Fava bean Flat pea ceral rye
fenugreek jackbean Chard
gama medic Lablab bean Chickpea
garden pea lupine common barley
garden vetch narrowleaf lupine common beet
guar narrowleaf trefoil common flax
hairy indigo red clover common oat
hyacinth bean sesbania common sunflower
Kura clover sweetclover common wheat
large yellow vetch white clover corn
lentil white sweet clover cultivated radish
mung bean Darnel ryegrass
peanut False flax
pigeon pea Field mustard
purple vetch foxtail amaranth
rhizoma peanut foxtail millet
rose clover gourd
roundhead lespedeza lacy phacelia
sanfoin little barley
snail medic pearl millet
strawberry clover plainsman amaranth
subterranean clover Prince-of-Wales feather
sunn hemp proso millet
velvet bean quinoa
water medic rape
white lupine red amaranth
white pea rocketsalad
winter vetch RS wheatgrass
Russian wild rye
safflower
Siberian kale
signalgrass
slender wheatgrass
sorghum
soybean
spinach
Sudex (Sorghum-sudangrass)
tall wheatgrass
teff
triticale
weeping alkaligrass
white mustard
Wimmera ryegrass

I hope you find this useful. Permaculture really can be a great decision-making tool.

Filed Under: Articles

Comments

  1. Sheri Cline says

    April 24, 2016 at 10:37 pm

    Many years ago as a child, I spent 2 weeks in the Palomar Mountains of California. The trees had a “black fungus” on them and I decided to write my Dear Uncle Jim a letter about what I had seen and to see if he could tell me what it was since my Palomar camp guides had no idea. My Uncle Jim “Cook” sent me a ton of materials and I’ll always remember my mother’s response; “He didn’t need to write a “Thesis” on it!” My Uncle changed my world with his “Thesis”. He took the time to collect information that he was passionate about and he shared it with me. To this day his passion for this earth has never faltered and I love him with all my heart for his caring. Your a special blessing and soul Toby Hemenway. I hope and I pray that your passion stays strong and connected. What an excellent post!

    Reply
  2. Elizabeth Nobbe says

    April 29, 2016 at 12:42 am

    I share Sheri’s appreciation for your wonderful way of teaching patterns, making a wealth of information applicable and life enriching.

    And I love the definition of ‘strategy.’ You made that word less daunting.

    Thank you, Toby Hemenway.

    Reply
  3. Bill Wilson says

    May 1, 2016 at 10:18 pm

    Wonderful Toby. Very nicely organized. What a gift. Thank you.

    Reply
  4. Nicole says

    May 3, 2016 at 2:02 am

    Thank you so much for this.
    Last year was my first year having my own yard or a garden. In an attempt to try to implement some permaculture principles that I really don’t know much about I had read to plant cover crops and so I planted white clover all over all my herb spirals and all keyhole gardens and between them. I realise now I should maybe not have planted them everywhere where I wanted veggies etc to grow too. How do I prevent the clover from coming back in those areas or what can I do so it doesn’t take over so much? It did help with moisture and weed control but was really aggressive and crowded out some of the vegetables. Any suggestions? Thank you!

    Reply
    • Jen says

      June 25, 2016 at 12:21 pm

      We did the same thing with red clover & are wondering the same as you now … we’d love suggestions too …. this is what we are trying this year as an experiment.
      1. Pulling out & clearing areas for veggies &
      cutting clover short, thinking that roots will be less deep & allow veggies some space.
      2. Laying strips or patches of cardboard down around veggies to keep clover back a little…. but this is a bit of a problem as it seems to attract slugs
      Our strawberries seem happy to grow interspersed with the clover … extra big & more strawberries… just a little more looking through the clover to find the fruit.

      Reply
      • Mary Rose Noll HIlkemeyer says

        May 8, 2019 at 6:33 pm

        i am happy with the way clover tends to keep the soil softer where my strawberries grow. I too am experiementing with permaculture gardening as i am wanting to keep the soil rich for the gardens i grow.
        Thank you for your sharing.

        Reply

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Toby Hemenway is the author of The Permaculture City and Gaia’s Garden: A Guide to Home-Scale Permaculture.
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