Building Swales on Contour

Swales are tree growing systems that are built on contour. What exactly does that definition mean? Let’s break it down.


First, a definition of contour. Contour maps show the topography of a given area. They tell you, visually, how steep the slope is. By looking at a contour map you can identify where hills, valleys, and cliffs are.

Understanding contour maps can be a bit difficult at first. The following video explains it really well.

So, saying that swales are built on contour means that they follow an individual contour line drawn on a map. If you walk along a swale, it should be perfectly flat, never going up or down hill.

Tree Growing

Next, let’s talk about a swale’s #1 purpose: to grow trees. Once you’ve outlined your contour, you create a swale by scooping up a mound of dirt along the contour line. (Also, a side note: Whenever you build any sort of earthworks, seed it with a cover crop as soon as possible to prevent erosion and to crowd out any unwanted volunteers/weeds.) Make sure that the mound stays loose enough that a tree can grow on it. You always, always, always plant swales with trees. In certain arid conditions, you may plant the tree inside the swale instead of on the mound, but there are always trees.

Since visual aids are so useful, here’s a video of Geoff Lawton explaining swales with a miniature “sandbox” version.

Swales help trees grow by catching water. Thanks to gravity, water always runs down hill. In other words, water flows perpendicular to the contour lines. A swale, which is built along a contour line, blocks the water’s downward path. If you’ve built your swale on contour, the water will pool along the level surface behind the swale. At this point, the water can seep into the soil to water the trees. The water also deposits any nutrients or organic matter it picked up while flowing down hill.

A System

Like many things in permaculture, swales are a system. The swale does benefit the trees, but the trees also benefit the swale. As the trees grow, their canopy shades the swale’s catchment and reduces evaporation. The tree roots stabilize the swale mound. The trees also create micro-climates for other plants and provide habitat for animals.

Because they are systems, swales will evolve over time. In particularly wet climates, a swale may eventually evolve into a chinampa. On steeper slows, swales will fill in with organic debris and end up looking more like terraces. In more arid climates, as swales mature, their anti-evaporation effect will create an oasis for other plants. Wherever they are, swales hydrate the land, recharge springs and aquifers, and nurture an abundance of life.

Here’s one more video with Geoff, next to a full-sized swale this time.

Quick Q&A

How far apart should you build your swales?

Bill Mollison’s Permaculture Design Manual says that in the most arid climates (10 inches of rain per year or less), swales should be 60 feet apart. In the most humid (50 inches of rain per year or more) the swales should be 12 feet apart. What if the climate you are working in fall somewhere in the middle? A bit of extrapolation gives this formula:

Distance Between Swales (in feet) = 72 - 1.2*(inches of rain per year) 

As an example, if you are designing swales in northern Utah where it rains 18 inches/year, you will get

Distance Between Swales (in feet) = 72 - 1.2*(18) = 50.4 ft

So you put about 50 feet between swales. (And don’t forget that the swale itself will take up around 5 to 15 feet).

That’s a basic overview of swales. If you have any questions or noticed something important that I missed, please let me know!

Spotlight: Joel Salatin

To break up the monotony of my engineering courses one year, I signed up for a “Small Animal Production” class with my university’s College of Agriculture. Partway through the semester, the professor showed us a video about Joel Salatin’s “Polyface Farm” that used some unusual farming techniques, such as rotating his cows to a new field every day, following his cattle with “chicken tractors”, and wintering chickens and rabbits together. Though he never said the word, I instantly recognized Salatin’s use of permaculture.

Photo Credit: nick v, Creative Commons licence.

Salatin’s Polyface Farm in Swoope, Virginia produces delicious, nutrient-dense protein by raising happy, healthy animals. He starts by caring for the soil–returning nutrients through animal manure and avoiding overgrazing by rotating his cattle. In turn, the soil provides rich forage for his animals. Salatin respects each animal’s natural instincts (“the pigness of pigs,” as he says) and works with, rather than against, their innate behaviors. He values his customers and works hard to provide the clean, nutritious meat and eggs that they’ve come to expect. Salatin has created a farm that’s sustainable, both financially and ecologically, and that his children want to continue.

Along with farming, Salatin teaches and writes. Over the summer, I read two of his books that explain how to make a profit through farming in an ethical and sustainable way: Pasture Poultry Profit$, which focus on raising meat chickens, and You Can Farm: The Entrepreneur’s Guide to Start & Succeed in a Farming Enterprise. Throughout both books, Salatin argues that ethical, sustainable farming not only produces healthier food for the consumer but can be more profitable, exponentially more enjoyable, and more psychologically fulfilling for the farmer. I’ve never felt more hopeful about the future of agriculture. Every agribusiness curriculum in the country should include Joel Salatin’s books.

Joel Salatin has accomplished more than I can ever fit into a blog post. If you want to learn more about Salatin and his farm, you can visit his blog, The Lunatic Farmer, or the Polyface Farm website. You can also find plenty of videos featuring him on YouTube. I’ve listed some of his books below.

Joel Salatin’s books:

What I Learned from Scientific Names

At the beginning of the summer, I set a simple goal: Learn the scientific name of one plant every day. I knew the basics of scientific names from high school biology. Every living species has a Latin-based name, categorizing them first into domains and kingdoms (animal, plant, fungus, etc.), all the way down to their specific genus and species (Solanum lycopersicum, or tomatoes). And I found a handy “botanary” to make the tongue-twister Latin names less intimidating.

I took on this project for two reasons. First, I wanted to sound more educated when I talk about plants. Secondly, I hoped that by taking a scientific approach to studying plants and learning their taxonomy, I’d gain a better understanding of how different species related–an important aspect when practicing permaculture.

On my phone, I set up a simple spreadsheet with Google Sheets where I could record the 1) genus, 2) species, 3) common name, and 4) any notes I wanted to remember about the plant. I started with my favorite flowers and garden plants. A quick visit to Wikipedia gave me the scientific name and plenty of fun facts. Did you know that bell peppers, cayenne pepper, paprika, and jalapenos are all the same species, Capsicum annuum? On the other hand, you’ll find around 50 different species of crab apple in the Malus genus. And peppermint, or Mentha x piperita, is actually a hybrid of watermint and spearmint.

I also used a guide book for common weeds from USU Extension. As I learned the names of various weeds, I started see them everywhere. I noticed where certain weeds grew and when each species came into bloom. I saw so much biodiversity that I had never noticed before.

And the results from my summer-long experiment? I learned the scientific names of just over 80 plant species. I don’t have most of the names memorized, but I do recognize the names when I see them. I’m already seeing benefits from my project. For example, on a Facebook gardener’s page someone mentioned that Solanum nigrum was invading their squash. Since I’d learned the scientific name for plants in the Solanum genus, I knew that this weed shares characteristics with deadly nightshades (likely poisonous on some level) and as well as to tomatoes, potatoes, and egg plant. If this Solanum “weed” tends to invade a garden full of squash, maybe the Solanum “edibles” will make good companion plants for squash. Time to look into a potato/tomato/eggplant + squash guild.

I’ll call that a success. If you have any experience with learning scientific names, with Solanum+squash companion planting, or anything else exciting, let me know in the comments! 🙂

Carbon + Nitrogen

Permaculture: a perfect coupling of science and tradition. Permaculture takes ancient techniques used by native people around the world and then refines them with modern science. Here, I want to talk about a scientific aspect of permaculture. Chemistry, to be specific. Let’s talk about carbon and nitrogen.


First the hot topic, carbon. Many people associate carbon with things like global warming, carbon footprints, and carbon taxes. But what is carbon, anyway?

Carbon, the 6th element on the periodic table, is the basic building block of life. In fact, one definition of organic is “carbon-based”. You find carbon in sugar, starch, oils, and proteins. Trees make their wood with carbon–about 50% carbon–and all plants need the carbon found in CO2 to perform photosynthesis.

Where else can you find carbon? Anything that’s biodegradable or plant-derived (think paper-products and cardboard) contains large amounts of carbon. Graphite (pencil led) is 100% carbon. Same with diamonds. The list goes on and on.

You are made of carbon. Carbon makes up 18.5% of your body, second only to oxygen. Life on Earth needs carbon to thrive.

Flowers in straw mulch, a good source of carbon. The straw will help retain water and–as it decomposes–add carbon to the soil.


Next, let’s consider nitrogen, a equally important chemical element. All life needs nitrogen to create DNA, chlorophyll, and protein. Nitrogen makes up 78% of the atmosphere, in the form of N2, so you breath mostly nitrogen. However, humans, animals, and plants can’t get nitrogen from the air. We need bacteria for that.

The nitrogen cycle describes how nitrogen gets from the air and into the biosphere. In short, certain plants (called nitrogen fixing plants) house beneficial bacteria in nodules on their roots. The bacteria take the nitrogen from the air and convert the nitrogen from the inorganic N2 gas to other forms, such as ammonium and nitrate, which plants can use. Thanks to the bacteria, both the nitrogen fixing plants and other vegetation can absorb the nitrogen from the soil. Animals can get nitrogen by eating the plants.

Often, soil does not have enough nitrogen. The lack of nitrogen in the the soil limits plant growth. You can add nitrogen to the soil through fertilizers, but that only fixes the problem temporarily. For a permanent solution–a permaculture solution–plant nitrogen fixing plants. Examples include beans, clover, locust trees, alfalfa, peas, and other legumes. These plants will give the soil a continuous source of nitrogen.

Give Your Garden Its Vitamins

Plants need more nutrients than carbon and nitrogen, obviously. But carbon and nitrogen are the key nutrients you need to provide. Now that you know this basic organic chemistry, how can you give your garden its “vitamins”? Consider three ways: protecting the nutrients you already have, feeding the soil, and letting nature do its thing.

Protect Nutrients

Rule #1: Never expose naked soil to the elements. Since plants take their nitrogen and many other nutrients through their roots, their roots need healthy soil to live in. However, exposing bare soil kills beneficial bacteria and washes away nutrients. Direct wind blows off the topsoil, direct rain causes erosion, and direct sunlight bakes the ground. The soil dies.

When landscaping, look for the least disruptive option. Need to remove some grass? Instead of tearing up the sod, try layering a few cardboard boxes on the patch of grass. After a few weeks, the grass with die, add its nutrients to the soil, and give you a clear patch of ground to plant in.

If you do have bare soil, cover it with mulch or a cover crop. Both will protect the soil from the elements and eventually add nutrients to the soil. Bonus points if your cover crop is a nitrogen fixing legume!

Feed the Soil

How do you add nitrogen to the soil? As one option, you can compost. The internet has countless tutorials on different forms of composting. Whichever method you choose, you’ll ultimately need 3 ingredients:

  • Carbon (from wood, cardboard, and other “brown” matter)
  • Nitrogen (from food scraps, animal manure, lawn clippings, and other “green” matter)
  • Water

Whether you compost or not, take advantages of whatever nutrients you have on site. For example, when you mow your lawn, let the grass clippings fall back to the ground, where they will decompose and release their nutrients back into the soil. Don’t throw away your nutrient-rich lawn clippings!

In hugelkultur, a method of adding carbon to the soil, you bury entire logs in the ground and plant on top of them. As the buried logs break down, they feed the plants and help the soil retain moisture.

Let Nature Be Nature

Consider a forest. No one fertilizes it, yet plants grow. They don’t just grow; they multiply and flourish. Nature knows how to take care of itself. Learn more about how nature fertilizes the soil and incorporate nature’s techniques into your own gardening.

One observation: Nature multi-tasks, using one plant for two or more purposes. You can multi-task by selecting nitrogen fixing plants that enhance your landscape. White clover mixes well with lawns. Peas add flavor to a garden. Many trees fix nitrogen as well.

Another observation: Every autumn, forests dump loads of nutrient rich leaves to the ground that eventually decompose and feed the forest floor. Follow nature’s example. Don’t throw away the leave! If you want plants to grow through the leaves, shred the leaves before reapplying them to the soil. Or, if you want to keep out some weeds, layer the unshredded leaves as a sheet mulch.

Take time to sit back, observe, and let nature teach you.

Niches: Spring Blooms

Nature tends to find niches, empty pockets of space or time, and fill them with life. Maple saplings find the niche in the sidewalk cracks, an unoccupied place where they can sprout. Deer wander into your backyard during the middle of the day, a niche in time when the humans leave to work and can’t stop them from munching on the rose bushes. With permaculture, we learn to recognize these niches and use them in design.

Weeds find a niche in rich decomposing leaf litter leftover from last fall.

For example, consider early spring. Buds form on the trees, and we anxiously wait for the first blossoms. But no color yet.

But we can have color if we design it.

Some flowers bloom in the early spring, just as the snow begins to melt, and then die back for the season before your grass grows tall enough to mow. By planting these early-blooming flowers, you can fill a niche in time and beautify the ground.

Which Flowers?

For my local area (Zone 6a), I’ve noticed these early spring perennials seem to thrive:

  • Crocus
  • Daffodils
  • Puschkinia
  • White Violets
  • Squill

(I’ll continue adding to this list as I notice more.)

Which flowers you should plant vary from location to location. Find out what grows best in your area. Talk to local experts, do an internet search, or simply walk around your neighborhood this spring and take notes of which flowers blossom early.

Have a favorite early-spring flower? Share in the comments!