Since 2009, I have learned from three forest gardens in three different forest habitats. In 2009/2010, I lived in the Coastal Douglas Fir zone on the Sunshine Coast of British Columbia, deep within a complex mix of secondary and old growth cedar, fir, Arbutus, and red alder trees, shading salal and evergreen huckleberry shrubs. In 2011/2012, I lived in a dry wheatgrass/fescue meadow surrounded by Ponderosa pine and sagebrush in Western Montana. Then in 2012 I came to a diverse commercial fruit orchard planted in patches within live oak/pine forest in the Sierra foothills of northern California.
First Lesson: Forest farming is a different mindset from agriculture!
Generally agriculture in North America has come from the grass-based plains and meadows of Europe. It relies heavily on cultivated grasses, or grains, and animals who graze on grasses. When I was in my early twenties and an intern at the Land Institute in Salina, Kansas, I was drawn to horticultural societies and agroforestry. At the Land Institute, we were envisioning a food system modeled after the diverse mix of perennial grasses and flowering plants living together in the prairie. This agriculture would be a perennial polyculture with its roots deep into the rich prairie soil undisturbed by tillage and the herbicides, pesticides, and fertilizers humans created to subsidize our tillage, disturbance-based agriculture. I kept wanting to talk about fruit and nut trees and the exciting diversity of small meadows at the forest edge. In exasperation one day, Wes Jackson, cofounder of the Land Institute, told me that when people get serious about agriculture, they plant grains. He was right, especially in a world with burgeoning population growth. So, for the next 25 years I studied, researched, and taught horticulture/agriculture and produced organic vegetables and fruits on my farm in Montana, with as little tillage as possible. I added legume living mulches in between my straight rows of vegetables, fruit bushes, and fruit trees. I called my reduced tillage, increased diversity system agricultural ecology. For videos and articles about my 17 years experimenting with agricultural ecology, living mulches, green manures, and conservation agriculture in Montana go to Conservation Farming, and Biodesign Farm research. But, in 2009, I had a chance to go beyond my conventional organic techniques and learn from listening to a forest.
Our human tendency is to chop down excessive plant growth, clear away brush, control the wildness, make nature neat. But, I knew from experiments with agroecology in Montana that if we do too much, we inherit the jobs of the organisms we get rid of and are forced to make and add fertilizer, apply fungicides to control disease, and insecticides to kill insects. There is also much research on the interactions of healthy functioning forests. Scientific research shows that the spatial, or structural, diversity in a functioning forest, what we call the "uneven texture" in a wild forest, enhances bird and insect diversity and balances pest outbreaks. In other words, the shape of a forest, from top to bottom, helps it maintain its own pest resistance. Our agrocecology experiments in Montana showed us the same thing when we diversified the below-ground and above-ground plant height and texture in our vegetable fields. Pest problems disappeared over time as a larger number of generalist predators and parasites came to live on the farm.
When I returned to Montana after selling my farm, I began with a meadow surrounded by Ponderosa pine forest. The land had been in my family for 35 years. The meadow was full of dry-site native and non-native grasses which I have watched cycle and change dominance since I was a child. The challenge was to go from this relatively wild meadow on the forest edge to food production with minimal disturbance.
Tilling in green plants pros and cons: Tilling in growing, established plants is a major soil disturbance, but at the same time, it adds a quick source of sugary, rapidly decomposing material that releases nutrients plants need when they need them.
I had learned from my experience in a British Columbia forest garden (see story below) that initial soil incorporation of high carbon material (like large, woody branches) along with low irrigation addition in a dry climate can be a challenge when you are trying to grow annual vegetables. What occurs the first season after high carbon materials are added to soils is tying up of nutrients like nitrogen and phosphorus and low yielding vegetable plants. I wanted to eat from my garden as soon as possible, so I avoided high carbon organic residue additions and instead mowed the meadow that was to become garden. I chose a slightly sunken area below a spring at the top of the meadow. It had taller, more vigorously-growing grasses and several moist-site grass species growing in it. The slightly sunken area was much wetter when I was a kid, 35 years earlier. Then I raked the mowed meadow and sowed dutch white clover.
The clover grew unirrigated with ease in the spring, struggled during a dry July and August, but came back vigorously in the fall. I mulched the clover and meadow grasses with alfalfa hay all winter, and only removed it to plant the following spring. Warm season crops were planted into black plastic and weed mat placed over the decomposing alfalfa hay. Cold season crops were planted directly into the hay mulch.
Fruit trees, like pear, apple, cultivated and wild plums, nut trees such as native hazelnut,and shrubs like Aronia, honeyberry, serviceberry, and golden currant were planted into the meadow grasses and mulched with alfalfa hay and vegetable trimmings. Eventually the viney squash plants moved down the hill and connected the woody tress and shrubs to the annual vegetable plants.
The annual vegetables grew vigorously and intermixed wildly, growing up as well as out.
Several varieties of winter squash and melons grew around and up the newly planted trees.
Despite what looked like a lot of competition for light, soil nutrients, and water, the harvest was bountiful the first season. I saw again and learned anew lessons about which plants can do well, even in slight shade with a lot of competition (one of my favorite shade and competition tolerant species is pictured: black beans, a stable in my diet all winter.)
The Sierra foothills forest garden is in the live oak/pine forest of northern California with wet, green winters and dry summers. The soil was disturbed a lot 30 to 35 years ago when Woodleaf Farm began and some of the forest trees were cleared to plant an orchard. I chose an acre of the oldest orchard with a diversity of mature fruit trees, berries, bamboo, native forest on two edges, with a riparian area and seasonal creek on the third side. Hence, I was able to create a forest garden as I had in Montana: soil disturbance was minimal. The diverse ground cover of plants was mostly left in place.The big difference is that I already had most of my mature over-story established: 25 year old, tall persimmons, 30 year old, even taller sweet cherries, a tall mulberry, mid sized Asian pears and European pears, and shorter apples, plums, and figs. I disturbed the soil beneath and around these mature trees minimally to plant the species I wanted to add, such as these onions and fava beans sprouting, mulched with alfalfa hay. In some places, I opened up areas of sunlight in the canopy. Now, I simply waiting for canopy closure and soil coverage to occur, which is happening quickly in this fertile soil! Canopy closure is important because our clay loam soil when exposed quickly degrades as it is pounded by rain and the hot sun in our Mediterranean climate. The regular shedding of leaves maintains soil fertility and feeds the soil food web. Co-mingling soil microorganisms break down plant residues and release nutrients into the soil in a form that can be taken up by plant roots. Now I am watching and paying attention to the dynamic process of managing forest garden interrelationships, such as these hardy kiwi vines mingling with grape vines on the edge of a grove of apples.
My goal is careful selection of tree, shrub, and vine species to blend into an interweaving of fruit, leaves, branches, and roots. I chose species with different growth forms, plants that have evolved to find and use light, space, and soil resources differently. I already had rows of both crown-bearing and stem-bearing fruit trees: cherries, apples, persimmons, pears, Asian pears, figs, a plum, and a mulberry. Some species bear their flowers and fruits at the top, in the spreading crown of branches pushed into the sunlight above shady interlacing forest branches. Others produce flowers and fruit along the stem and lower branches in relative shade, like sweet cherries. Again, it is all about managing the light resource. Sunny, open-loving species are mixed with shade tolerant species. In order to mimic the closed fertility cycle of a forest, trees are mulched with fallen leaves and twigs regularly. I brought in only two fertilizer inputs from outside the forest garden: spoiled alfalfa hay and some chipped branch wood yard waste compost to mulch the newly planted trees, shrubs, vines, perennial herbaceous plants (such as asparagus and artichokes), and annual shade-tolerant vegetable plants (such as Brussels sprouts, kale, cabbage, broccoli, onions, and fava beans). Mowing and mulching the ground cover is the main fertilization. Lots of woody biomass and decomposing leaves have been added over the years due to natural winter defoliation and pruning. Trees are pruned at least once a year and the branches and green leaves are broken up with a mower and scattered beneath the trees.
In British Columbia, we made raised beds filled with wood and chipped branches and planted crimson clover over the surface of the beds. The crimson clover germinated within 7-10 days in the raised beds planned for vegetables in spring 2010. I used crimson clover because it is a fast growing annual, which I thought would be set back over the winter and easy to till in the spring. I also planted mostly dormant 2 inch by 2 inch native wild flower transplants from my native plant nursery in Montana into one of the raised beds late fall 2009. In coastal BC, the crimson clover began growing again early in the spring of 2010. It grew assertively, flowering profusely and providing an early pollen source for insects.
In the spring of 2010, we decided not to add any fertilizer (manure or seaweed, for example) and not to till in the crimson clover as a green manure. We disturbed the clover only minimally by making rows into it with a hoe. Then we planted late in the spring directly into the un-mowed crimson clover, knowing that it is an annual and would be dying back soon after flowering and seeding. It was a rainy spring and the clover continued to grow and shade the vegetable seedlings and transplants well into June. Then it stopped raining in July and got very dry. The crimson clover dried up and died after setting seed. I mowed the standing, dry clover hay between the vegetable plants in July and began irrigating lightly. We used only the bare minimum of water. In fact, July was so hot and dry that some of the vegetable crops were water stressed. By mid July the shed crimson clover seed was germinating beneath the vegetables and the dried crimson clover plants I had mowed into a nice mulch around them. The native flower garden was doing very well, blooming despite very little or no added irrigation. In fact some of the native perennial flowers planted in fall 2009 grew more vigorously than I had ever seen my native plants grow in any other garden or restoration project.
The vegetables did not respond as well. Overall, the first year vegetable garden grew slowly. Crops planted by seed did more poorly than transplants. It was hard to dig in the soil to plant. The fluffy texture of an undisturbed forest floor, complete with a soil full of open spaces for air and water to move freely, was lacking. Potatoes and carrots did not produce much foliage and developed small roots. The yield was very light. Nutrients were tied up as the high carbon woody material broke down (releasing nutrients and creating air pockets in the process). Larger woody material has a greater carbon to nitrogen and carbon to phosphorus ratio than forest leaf/twig mulch and much larger ratios than most organic fertilizers, such as clover green manure, manure or alfalfa meal. So, in the short run, nitrogen and phosphorus were deficient for annual vegetable plants that are bred to use the excessive amounts of these nutrients we usually supply. The clover did relatively well because it does not have such a high nitrogen requirement. The high ratios of carbon to nitrogen and phosphorus inhibited root growth in the short run. Also, our nutrient cyclers, the soil food web, were sluggish, rebuilding slowly after our excavator disturbance. Here is some more detail about what probably happened when we added a lot of high carbon plant material to the soil. Fresh, green, succulent residues (like young, leaves or newly-cut grass clippings) have higher nitrogen than carbon levels in them and more sugars and proteins that decompose rapidly. More mature, dried out, and especially woody, residues have less nitrogen and more carbon and higher lignin levels. Lignin is a tough, hard-to-break-down component of plant cell walls and is most abundant in woody species like trees. These materials decompose more slowly than young, fresh plant residues. For example, in one study, young and mature grass and straw were compared as soil additives. Young grass had the highest nitrogen level (3.7 percent), mature grass was medium (1.5 percent), and straw had the lowest nitrogen content (0.5 percent). Straw, conversely, had the highest carbon content and therefore the highest carbon to nitrogen ratio (85). The carbon to nitrogen ratio of young grass was 12, while mature grass had a Carbon to nitrogen ratio of 29. Lignin content of these three plant residues was also compared. Not surprisingly, straw had a high lignin content; mature grass, medium; and young grass was low in lignin. After composting these materials for 180 days, which material do you think formed the most humus? The young grass! Straw formed the least humus and mature grass was intermediate. Young grass also lost the most nitrogen during decomposition (more than 50 percent). In other words, as the young, green, succulent material broke down, they rapidly released nitrogen directly into the soil where plants want it. The green material decomposed into the greatest amount of humus. This is important because humus is the preferred home of the soil food web and is the sponge in the soil that manages water, releasing water into the soil when soils are dry and storing it when there is too much water in the soil around plant roots. In the short term, high carbon materials are usually not able to feed plants, like annual vegetables, that want quickly available nutrients right at their roots.
In time the high carbon materials will break down, the soil texture will loosen up, the soil food web will rebuild, and plants will grow with vigor.
Annual plants growing in greenhouse beds grew much better. These beds were amended with seaweed I added seaweed in the fall of 2009 and worked it into the beds so that it would have the time, oxygen, and humidity to decompose before planting in spring 2010. Greenhouse plants produced a good amount of edible foliage and fruits. The other important factor in the greenhouse was that irrigation was not lacking and, due to the enclosed environment, humidity was higher. Because plants were protected from drying winds and direct sun, they were never water stressed. Also there was plenty of moisture for soil microbes to use as they broke down the seaweed I added.
Forest gardening makes ecological sense. Thirty percent of the surface of the earth is covered in temperate forest. Where people cut down forests for wood and to clear land for grain and livestock agriculture, there is often erosion, soil loss, soil degradation, and certainly an enormous decrease in plant , animal, amphibian, microbe, and insect biodiversity. My forest garden is based on more northerly tree fruits and forest plants and includes: trees, such as sweet cherries, wild and cultivated varieties of plums, pears, apples, mulberries, persimmons, figs, pecans, and shrubs, such as raspberries, blueberries, boysenberries, blackberries, wild and cultivated varieties of currants, aronia, honeyberry, and figs. Wild and cultivated strawberries, native wildflowers, wild edible greens (such as miner's lettuce and dandelions, herbs, Shitake mushrooms, and perennial vegetables, such as asparagus and Jerusalem artichokes cover and shade the soil. Vines climb on trellises with fruits of hardy kiwis, grapes, annual vegetables. such as Scarlet runner beans hanging beneath the foliage. It is a 3-story effect rather than an agriculture all on one plane, such as a grain or tomato field.
Masanobu Fukuoka, the premier natural gardener, once said, "The ultimate goal of farming is not the growing of crops, but the cultivation and perfection of human beings." How we garden reflects who we are. Those of us who live in forest ecosystems spend a lot of energy plowing, mowing, cutting, weeding, and spraying to keep the forest from entering our gardens and farms. Gardening along with the forest, rather than fighting it back seems a kinder approach. One of the things humans are least apt to change is their diet. As I write this there is unrest in the world blamed partially on a scarcity of the food to which we have addicted ourselves, grain. Corn, wheat, and rice are expensive and hard to come by in some parts of the world now. Perhaps it is time to cultivate and perfect new ways of thinking, seeing, and eating. They are intertwined, just like a healthy forest. More on the details of forest gardening to come!