PERMACULTURE TREES: Why, Where, How?

Trees hold many of the great ecosystems of the world together, stabilizing the soil, collecting dew and dripping it to earth, shading the land, and cooling the air through evapotranspiration. Trees are an integral part of how water moves around the world, both in the air and on land, and in this age of climate instability, trees are some of the very best tools that we have to fix broken ecosystems and grow resilient and productive food systems. This lesson is about how we design using trees to heal the land by developing tree-based permaculture systems. We'll look at the main climate types on earth, the tropics, drylands, and temperate climates. You can skip right to your climate zone by following the timestamps in the description. In the Permaculture Designer's Manual, Bill Mollison talks a lot about why it's so important that we focus food production on tree crops in the tropics. In the wet tropics, it's warm and moist all year round, so plants never get a break from growing. They just grow and grow. They're constantly uptaking and recycling nutrients. And what this means is that the soil doesn't hold nutrients. The nutrients are continually being used for plant growth. So when you remove a forest, you remove the nutrients from the system and are left with poor soils that are then exposed to the heavy tropical rain and sun, which further leaches nutrients. It's a vicious cycle of degradation, and it's the reason why in permaculture we believe the vast areas of wet tropical environments should remain in forests and not be used for wide open fields and pastures. So the way to grow food in the wet tropics is by growing a multi-story food jungle garden. Here's one example of how that can look. The highest levels are productive palms, which produce a variety of different yields like coconuts, oils, and the juice for wine. The next level down are leguminous trees. They build fertility in the system because they literally take nitrogen from the air and release it into the soil. They are living fertility factories. Many produce a pod or a seed that can be harvested, and many have small leaves and open canopies that let a lot of light through so the layers below can still harvest sunlight. The next layer down are the fruit and nut trees of all types. Mangoes, bananas, jackfruit, papayas, breadfruit, cashews, citrus. The list goes on and on. You see the palms and the legumes are spaced out, so there's still a lot of areas where direct sunlight's getting through to grow a massive diversity of tree crops below. I've been to places like this and it feels like the Garden of Eden. We also have vines growing up the trees like pepper and vanilla. These can be really important cash crops in a food jungle that don't take up extra horizontal space. Then finally, we get to the understory at the ground level where there's an awesome assortment of crops to be grown. Here are dappled shade lovers like coffee and ginger, root crops like cassavas and sweet potatoes, and countless herbs, medicines, and fiber plants. Many of these understory plants actually do much better with the filtered light provided by these trees from above. If a plant requires more light, you can plant it at the edge of the forest or create clearings where more sunlight gets through. Now, you'll notice that I show a pretty wild assembly of plants. You can actually use the same principles of growing a multi-layered food forest, yet you can create a much more regular pattern that's easier to harvest in a farm setting. There's an entire field of study called agroforestry that's all about the design of these tree systems. Now, most people look at deserts today and they think that they were always these barren treeless wastelands. But the truth is that most deserts long ago, before they were impacted, were actually teeming with life and had biodiverse forests, desert forests. So what permaculture does is it shows us how we can redesign these degraded landscapes and bring deserts back to their highest order of biology and biodiversity. The key to growing trees in the desert is to start by establishing small areas where water and nutrients are concentrated. This means sculpting the earth to create rainwater harvesting basins that collect storm runoff. This creates sunken wet zones where life begins to concentrate. The first trees to plant are tough native trees, ideally those that fix nitrogen from the atmosphere and bring it into the soil below. These types of hardy trees are called pioneer species. The water harvesting structures can look like a lot of different things and their design will determine the layout of the tree planting. So right here, I drew the classic half moons we see throughout the African Sahel. And here, I'm drawing an on-contour swale, which is like one elongated sunken basin. There are lots of ways to create wetter microclimates that provide extra water for a tree to grow in a dry land. Once a tree is growing in the sheltered microclimate, it becomes a nucleus for other species of plants and animals because it creates the conditions for other things to live, like shade, shelter, wind protection, and even food. So the soil and climate conditions are changed within that nucleus and eventually more tender species can be added to the protected understory of the tree. But the magic is in the repetition of the pattern when we plant these concentrations of life down throughout a watershed. Establishing many trees in the desert landscape starts to change the whole environment and the sheltered spaces that are created are much better for growing crops than the open desert. This is called alley cropping, and it's a great way to integrate trees into field agriculture in any climate. It's not just shelter from wind and sun that trees can provide for desert crops, but salts tend to build up on desert soils when irrigation waters evaporate, and trees transpire and keep the salts from accumulating at the surface. Once these soils are improved around these hardy pioneer species and water is now soaking into the ground, more valuable fruit, nut, and timber trees can be integrated into the newly improved microclimate. So even though you may need to do long-term irrigation of exotic fruit and nut trees, many hardy native tree species produce yields without needing any extra water besides rainfall, like pods, flowers for nectar, and fodder for animals. So finally, we got to the climate where I actually live in, the temperate climate. And the further and further we get from the equator, a new limiting factor emerges. Sunlight. In many ways, the permaculture tree systems and temperate climates use a lot of the same principles as in the tropics. With diverse, multi-layered food forests, productive plants and fungi in the shady understory, vines growing up trees, and many dimensions of production. But the big change is that the architecture of the trees needs to be intentionally designed around maintaining access to the scarcer sunlight. You can see here that this tree assemblage steps down towards the direction of the sun in winter, with the tallest trees in the back stepping all the way down to the field crops in the front. It's like a solar amphitheater. So this design means that every plant has access to the sunlight as the angle of the sun gets lower and lower in the winter months. In fact, the trees can even reflect some of that sunlight into the open area below. Temperate climates are places where you can actually grow annual field crops without destroying the topsoil. So the key design question to ask is, how can I incorporate trees into annual cropping areas, like on the field boundaries, in riparian zones, along roadways? There's no reason why we can't have trees integrated throughout the temperate climate agricultural landscapes using permaculture and agroforestry systems. Remember, when we have a matrix of trees growing throughout the wide landscape, it holds the ecosystem together by moderating how water flows, stabilizing soils, providing cover for the movement of insects and birds and other mammals, protecting from wind, moderating temperature. Trees knit the landscape together, especially biodiverse native forests. As a general rule of thumb, it's suggested that at least 30% of any design landscape be covered in trees. 30% forest cover is also the goal of many nations on the earth, with some committing to much higher forest coverage. But if you're designing any landscape, think about starting with 30% tree cover, and then you can increase from there. So there you have it, folks. This has been just a really general overview of how you can use trees to heal the land and provide for our needs at the same time. So get planting. Are you ready to design your own thriving permaculture site, build a meaningful career, and learn to restore ecosystems? In my 30 years as a permaculture designer, studying the best examples around the world, I've put everything I've learned into Oregon State University's online permaculture design courses. These online classes are the ultimate way to start mastering permaculture. My team and I will guide you through every step of the permaculture design process, with personalized mentorship in a small group setting, and over 100 hours of in-depth video training. By the end of the class, you'll create an advanced permaculture design for your chosen project, gaining the professional skills that you'll need to start healing the world. So if you're ready to be part of the solution, then this is your starting point. Click the link below to sign up, and I'll see you in class.