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Next-Generation Polycultures

Excerpted from Paradise Lot: Two Plant Geeks, One Tenth of an Acre, and the Making of an Edible Urban Oasis by Eric Toensmeier with contributions from Jonathan Bates, available from Chelsea Green January 2013. The book tells the story of our permaculture garden from design through co-evolution nine years down the road.

One spring day in 2009, I gave a garden tour to a young man from New York City who had a forest garden in his tiny front yard. In a ten-by-ten foot patch, he had planted an Asian persimmon and a full set of companions for nitrogen fixation, groundcover, and additional perennial foods. As we walked the garden, I pointed out many species, and we sampled some fruits and greens that he had never tasted before. Usually by the end of a tour, people say how impressed they are with our garden. But this young man had obviously read my books.

“So where are the polycultures?” he asked.

“Um, all around us?” I replied sheepishly. I pointed out a few areas where species were actually playing nicely together.

But he was right. It was our herbaceous layer that was a disaster. When we had put in this garden, we knew little about most of the hundred and fifty or so perennials we were planting. We had a general sense of whether they wanted sun or shade and whether in theory they stayed put in a clump or ran in every direction, but we had little in the way of firsthand knowledge of their mature form and behavior. Nor did we understand the principles that make for successful plant combinations. As a result we just planted them out more or less randomly within the herbaceous layer and hoped for the best.

Within a few years our perennial plantings were a riotous tangle. Plants sprawled over each other. Robust species smothered delicate rarities. Vines like groundnut climbed high into our pear and beach plum trees, competing for sunlight.

Our visitor from New York inadvertently made a point that Jonathan and I needed to pay attention to: we resolved that starting the following year we would remake our polycultures in line with what we had been learning in our own garden and beyond.

Back in 2004 Jonathan and I set some pretty lofty goals. We hoped to create a “backyard foraging paradise,” a “megadiverse living ark of useful and multifunctional plants from our own bioregion and around the world.” By 2009 we had essentially realized these goals. Our grand experiment had given us a garden with such diversity that we had seventy species of perennials with edible leaves. We also learned that only some of them were really worth eating, and others just didn’t want to grow for us. We had cast a wide net and now needed to pluck out the best of what our exploration of diversity had offered us.

We had aimed for three hundred species on our tenth of an acre. At this point we have roughly two hundred perennial or self-sowing species, with perhaps one hundred sixty or so of those edible in one fashion or another. I’d bet that we’ve tried and killed pretty close to one hundred others over the years. Having met our initial goal of testing maximum diversity, we had to refine things.

We revised our goals to a much simpler statement: “to grow the things we like to eat, that grow well for us, and assemble them in functioning polycultures.” No need for bad-tasting crops that grow well or things we love that always die. No need for a tangled mishmash of crops that can’t be easily harvested and shade each other out.

The garden itself suggests many polycultures to us. Sometimes this is a case of “Your peanut butter is in my chocolate.” For example, we were growing walking onions in one area and Hidcote Blue dwarf running comfrey in another. They grew into each other’s areas under a jostaberry and got along wonderfully. After observing for a while, we weeded out a few garlic chives and sweet cicelies in the following spring, pruned up the josta to let in more light, and transplanted a bit of the comfrey and walking onions around to spread the polyculture even further. Two years later both humans and plants seem quite happy with that arrangement.
A lot of forest garden species are a double-edged sword. The problem is that “low maintenance” often translates into more success than you might like. Hog peanut is a great example. This native wild bean can grow in shade and fixes nitrogen, making small edible beans above ground and larger ones underground. A self-seeding annual, it grows from these underground seeds every year. It germinates rather late, then really takes off through the summer. Once it has been in place for a season or so, hundreds of seedlings will come up to form a dense carpet in spring; their viney growth will smother almost anything less than three feet tall, so you need to weed them constantly or cut them back from other smaller plants. We have learned to match hog peanuts with taller species. Under a five-foot jostaberry, hog peanuts are welcome as a shade-loving, nitrogen-fixing groundcover. Under a two- to three-foot gooseberry, they provide excessive competition (and just try weeding them out of a super-spiny gooseberry).

We also learned that some of our species, like ramps and toothwort, or native wasabi, come up early in spring but disappear by June or so. We realized that hog peanuts, which must germinate from buried seed each year, are getting large just at the time that ramps and toothwort are dying back. We already had a nice patch of ramps growing in the shade of our pawpaw trees, and in 2010 I planted some hog peanuts there with good results. I would not have necessarily known that from reading a book; it took repeated observation to figure out the cycles of these plants in our garden.

Harvesting hog peanuts adds another layer of challenge. The below-ground beans are nice for fresh eating or cooking. They’re also only about a quarter inch round and covered with a brown fuzzy coating, so they are almost indistinguishable from clods of dirt. (Peeling back the fuzz reveals a beautiful white-and-purple-striped bean inside.) Although books on wild edibles tend to say that hog peanuts grow in the soil, in our garden we find them mostly right between the mulch and soil layers. Digging around to find them messes up the mulch, which is often incompatible with other polyculture companions.

In 2011 we decided to try some new variations on our three-brothers polyculture. In April we removed everything from an unsatisfying bed and went over it with the broadfork. We tried three versions of sunchoke polycultures in beds that had been prepared with aluminum-flashing rhizome barriers. The first was our classic three-brothers combination. The next was sunchoke and woolly bean, a native annual wild bean. The third was sunchoke and hog peanut.

This last was the one that I was most excited about and secretly betting on. Sunchokes meet all of the criteria as a companion for hog peanut: they emerge early and are sizable by the time hog peanuts germinate, and they reach up to eight feet. No chance that hog peanuts could smother them! Hog peanuts can fill in for both the groundnuts and Chinese artichoke, as they both climb and sprawl along the ground as they fix nitrogen. The sunchokes have to be dug every year anyway, so while you were digging them you’d surely find many hog peanuts as a bonus harvest, even though they are not necessarily worth harvesting as a crop on their own. At least the harvest practices of each species are compatible.

My visits to Las Cañadas and other tropical permaculture sites provided some models I wanted to play with at home. One simple pattern that I should have thought of myself is to grow edible vines on nitrogen-fixing trees. There’s no reason to waste all that space on fertility when it can also serve as a living trellis.

One of the first things we planted when we moved into the house was a Chinese yam on our front porch. It grew as an ornamental for years and made tiny aerial tubers that I thought of as a novelty crop. After three or four years, I noticed that it was making a lot of those little tubers. Marikler wanted to try them, so we cooked some up, figuring they would just be okay. To my surprise, with a bit of butter and salt they tasted like new potatoes. Today we call them “yamberries,” though of course they are not really berries, just tiny tubers growing on a vine above ground. I estimated that our single mature vine produced three or four gallons of little tubers, but the way it was growing on our front porch made harvest difficult.

Jonathan and I talked it over and decided that Chinese yam would be the first vine we would try to grow in a living-trellis system. We had recently cleared out our Regent juneberries and had an empty space in that patch. We planted out three Siberian pea shrubs with the goal that we would prune them to a T or Y shape to serve as a nitrogen-fixing, living trellis, perhaps with bamboo poles laid across them. Unfortunately, even though I knew better, I did something stupid: I planted the Chinese yams at the base of the pea shrubs in the same year, without giving the shrubs a chance to grow and get established before having to compete against aggressive sprawling vines. I’ve spent the last few years pruning back the vines to try to let the shrubs get established. It also seems as if Siberian pea shrub has persistently failed to take off in our garden. Despite these multiple challenges, I do feel that this model can eventually work. We’re going to try swapping out some of the pea shrubs for red alders.

Also in my travels I have seen the benefit of growing something edible and sun-loving in the understory while waiting for trees and shrubs to establish. In 2009 and again in 2010, I had the chance to visit the demonstration farm of the Educational Concerns for Hunger Organization (ECHO) in Fort Myers, Florida. I was captivated on both visits by a living-trellis system that they were establishing using a widely practiced tropical living-trellis polyculture. The long-term design is for passionfruit vines on a nitrogen-fixing, living trellis of madre de cacao, with an overstory of coconuts. The first time I saw this system, the trellis trees were young and the understory was planted out to eggplants. Why not get a yield while waiting? They hadn’t even planted the passionfruits yet, nor had they been planted when I returned a year later. Even in the tropics, it takes time to get a trellis tree strong enough to support fast-growing, vigorous vines.

I have also observed this establishment pattern at the Central Rocky Mountain Permaculture Institute in Colorado and the New Forest Institute in Maine. Growing annual vegetables, strawberries, or other crops gives you something to eat while you wait, and sometimes the care like watering, weeding, and fertilizing that you give those annuals is better than what you might give a somewhat forgotten, not-yet-fruiting tree. Our first priority for our yamberry trellis understory had to be a nitrogen-fixing groundcover that didn’t mind having a tarp thrown on it so we could shake down the yamberries. That did not preclude growing something between now and yamberry maturity, nor did it preclude growing some spring ephemeral species that will be dormant by yamberry harvest time. For a legume, we went with birdsfoot trefoil, an urban-adapted nitrogen-fixer similar to clover. We planted out the area densely with Jonathan’s family heirloom elephant garlic and had nice yields, as it was still essentially full sun. We also grew some perennial Kurrat leeks, which had been languishing in the shade for a few years and had never flowered. We added ramps and edible camas bulbs so that in the long term we can have a spring yield as well.

Though they look good on paper, plenty of the polycultures we have tried have not worked well on the ground. We designed an all-native polyculture to grow in the part shade under our Norway maples. The goal was to provide a living trellis and useful groundcover support species for a native perennial wild bean that grows in part shade in tangled thickets. For the living trellis, we selected false indigo, a native shrub that is a common urban weed in Holyoke that we expected to thrive. Sadly, after a year of growth it could charitably be described as six inches tall and half dead. The common blue violets that we knew were already in our understory thrived here, but our attempt to grow native wild garlic as the violets’ understory companion was a complete disaster. None of the plants seem to have come up at all, though it has a reputation as a fairly ferocious weed. The beans did fine, which gives us a two-out-of-four success rate, not our most shining polyculture demonstration.

One of the best of our next-generation polycultures is the reworked understory for our beach plum. We love these newly domesticated native fruits and they grow next to the main path that we use on tours, so we wanted to show the best we had to offer in this area. We didn’t feel the need to add nitrogen-fixers, as the yamberry–pea shrub polyculture is right next to the beach plums. We planted a living barrier of dense Profusion sorrel between our beach plum area and the yamberry zone, so that the different groundcover systems would not contaminate each other.

By dividing our green and gold and dwarf coreopsis, we were able to thoroughly plant out our beach plum understory with clumps about twelve inches apart. By the end of one season, they were filling in; it is clear that next year they will form a dense evergreen carpet and a lovely groundcover. Of course we wanted to see what other food plants might be compatible with this groundcover. After some thought we planted bulbs of ramps and camas, as we had in the yamberry area. Our beach plum zone is showing every sign of shaping up to be a nice patch of low-maintenance, food-producing, pest-controlling, edible forest garden. It will also be an attractive corner, with white-flowering plums, yellow-flowering groundcovers, and blue-flowering camas in springtime. Every species in this polyculture is an eastern native with the exception of West Coast camas, which perhaps could be swapped out for the native eastern variety.

We have a question that helps us evaluate new polycultures on paper before we go to the trouble of planting them: Is every species going to be happy with the niche we are providing it? Of course ideal conditions yield the best production, but sometimes you just can’t create these environments and have to accept reduced yields or imperfect health. Other times you actually want to slow something down by keeping it unhappy, an idea I learned from Steve Breyer of Tripple Brook Farm. We do this with fuki and water celery; it’s more fun to design a way to slow them down with dry shade than to weed them continually in an ideal, wetter spot.

We are as glad to borrow ideas from other gardeners as we are to imitate what we find in nature. While replicating polycultures we have seen in Florida and Mexico involves substituting hardy for tropical species, when we look to Martin Crawford’s remarkable English forest garden we can often directly replicate a species combination. One that I saw covering a good-sized area when I was there in 1997 is comfrey with mint. This exemplifies the pattern of tall clumping species (comfrey) emerging like islands out of the sea of lower runners (mint). The mint is aggressive and smothers anything smaller than it, but it doesn’t stand a chance against a large clump of comfrey. Both plants provide nectar and habitat for pest control, and combined they make a satisfactory groundcover. In Martin’s two-acre garden, this polyculture takes up lots of space in the understory. In our case we have little room to work with and are concerned about allowing mint out into the more civilized areas of the garden. Our solution? We planted mint and comfrey at the base of the house along the vehicle access alleyway to the south. The shady conditions help keep both plants in check and being driven over by a pickup truck every once in a while reins in their ambition. We cut the comfrey for mulch and chicken food and use the mints for tea. This polyculture has been growing there for eight years and has remained relatively well behaved and not spread much beyond its confines.

A widespread practice in the tropics is the use of fodder banks, trees and shrubs closely planted about one to two feet apart that are coppiced one or more times every year, the leaves fed to livestock. At both Las Cañadas and ECHO, I’ve seen examples of coppiced woody plants such as moringa, katuk, and chaya producing leaves for human consumption. These systems can be very productive because the mature root system of the tree provides lots of energy for quick resprouting and rapid growth of tender young leaves.

Though our woody leaf-crop species are not quite as glamorous as what we’ve seen in Mexico and Florida, Jonathan and I decided to try this model of food production. One of the benefits of this practice in colder climates is that the leaves on coppiced leaf crops remain tender and edible far into the summer, long after most perennial vegetables have wrapped up their season, at the end of May. In an area that was an overgrown mishmash of water celery, comfrey, sweet cicely, and assorted other odds and ends, we began planting our human fodder bank. We started with littleleaf linden, which Martin Crawford recommends as an edible leaf crop in Creating a Forest Garden. I’ve consumed lots of linden leaves over the years—unlike many perennial vegetables, they can be eaten raw—and find them perfectly palatable, if not remarkably delicious.

To our established lindens, we will add a variety of edible-leaf mulberry. Most mulberry leaves taste pretty terrible, but they are as high as 30 percent protein, and I learned from an unforgettable Mexican lasagna at Las Cañadas that there are some fine varieties for eating, though they must be cooked. We’ll also be trying the fragrant spring tree, which is cultivated by Amherst Chinese, a local restaurant that serves the leaves in frittatas. Its strong garlic flavor is an acquired taste, but we are going to give it a try with a flaming magenta variety called Flamingo.

We may also try a few edible-leaf gojis, which I like, though no one else in the house cares for their leaves. To ensure high production of all these leaf crops, we want to have a nitrogen-fixer in the mix, preferably one that coppices just like the other members of the polyculture. Many nitrogen-fixers are poisonous, however, and we wouldn’t want any mixups like our daffodil–garlic chive confusion. Bush clover seems to be the right species for the job. Though the leaves are no more delicious than red or white clover, they are nontoxic and considered edible. I have found them to be a serviceable if not gourmet food. At least they are not going to poison us if they end up in the stew by accident. And bush clover grows vigorously in our urban soils and can be coppiced multiple times a year for mulch.

Underneath our coppiced trees and shrubs we will grow some kind of shade-tolerant groundcover, with luck something that provides some pest control, edibility, or other useful function. It may seem strange that we are planting more edible leaves, given that we already have too many. But I like linden and mulberry leaves, and we would be glad to have more perennial leaf crops in summer. Whatever surplus we have would make great rabbit or tilapia food, as we are hoping to add more microlivestock. But even if we had all the leaves we could ever want, neither Jonathan nor I could ever resist the allure of this powerful mix of new crops and a new perennial production model.

Eric Toensmeier

Eric Toensmeier is the award-winning author of Paradise Lot and Perennial Vegetables, and the co-author of Edible Forest Gardens. He is an appointed lecturer at Yale University, a Senior Biosequestration Fellow with Project Drawdown, and an international trainer. Eric presents in English, Spanish, and botanical Latin throughout the Americas and beyond. He has studied useful perennial plants and their roles in agroforestry systems for over two decades. Eric has owned a seed company, managed an urban farm that leased parcels to Hispanic and refugee growers, and provided planning and business trainings to farmers. He is the author of The Carbon Farming Solution: A Global Toolkit of Perennial Crops and Regenerative Agricultural Practices for Climate Change Mitigation and Food Security released in February 2016.

7 Comments

  1. I enjoyed this very much, it was thorough and very informative. Where do you live? I didn’t recognize a number of those natives. Thanks, Morgan

  2. Great article!
    I would love to see articles like this listing Genus/species names as well as common names, although in this case and with this author I imagine they will probably appear elsewhere in the excerpted work.
    It’s not just that I’m a taxonomy geek… Having knowledge of phylogenetic relationships as encoded in taxonomy can help designers in many ways. (e.g.) Narrowing a search for local endemics that fill similar niches/functions; Identifying potential vectors and risks of disease transmission among related taxa etc.
    My 2c

  3. Good point Ben, and yes they are in the book. In fact my editors pulled them from the text and put them in the back for readability.

    Here goes: walking onion (Allium cepa proliferum); Hidcote blue comfrey (Symphytum spp.); jostaberry (Ribes x culverwellii); garlic chives (Allium tuberosum); sweet cicely (Myrrhis odorata); hog peanut (Amphicarpa bracteata); ramps (Allium tricoccum); sunchoke (Helianthus tuberosus); woolly bean (Strophostyles helvola); Chinese articoke (Stachys affinis); groundnut (Apios americana); Chinese yam (Dioscorea batatas); Siberian pea shrub (Caragana arborescens); birdsfoot trefoil (Lotus corniculatus); elephant garlic and Kurrat leef (Allium ampeloprasum); camas (Camassia quamash); false indigo (Amorpha fruticosa); wild bean (Phaseolus polystachios); common blue violet (Viola sororia); beach plum (Prunus maritima); green and gold (Chrysogonum virginanum); dwarf coreopsis (Coropsis auriculata nana); fuki (Petastites japonicus giganteus); water celery (Oenanthe javanica); comfrey (Symhytum x uplandicum); mint (Mentha spp.); littleleaf linden (Tilia cordata); fragrant spring tree (Toona sinensis); edible leaf mulberry (Morus alba); goji (Lycium chinense); bush clover (Lespedeza bicolor).

  4. Thanks for sharing your experiments with us!

    I was especially interested to hear what you did with the understory of your pawpaw. It seems likely to me that the good timing between the wooly bean and ramps/toothwort is due to their origins in the same ecosystem. I think it’s wonderful how gardening can provide insight into deep biological relationships that we otherwise might never notice.

    I also think that maybe you shouldn’t give up on your false indigo/”wild garlic”/wild bean polyculture just yet. Norway maples are notoriously difficult to grow things under. As this blog post explains, their roots are extremely dense and competitive. The plants that are associated with the Norway maple’s understory in its native range are similarly-invasive species over here, such as honeysuckle and lily of the valley.

    Maybe under a friendlier canopy your guild could thrive?

  5. I understand you can’t publish where you live but what zone do you live in? It would help knowing if any those plants you mentioned would grow in my zone 7-8

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