Courtesy Jon Roberts/Wikimedia
Lasagna gardening. Sheet composting. No-till gardening. You’ve probably come across these and similar gardening techniques before. They are all slightly different variations on building a raised bed from layers of organic matter, which rots down right where it is, getting better and better as it composts in place. Techniques such as these promise that you can improve tilth, preserve soil structure, and create the garden bed of your dreams without a lot of backbreaking labor or expensive, imported garden soil.
Although some of these published methods offer specific “recipes” to create ideal, no-till beds, the basic technique is simple: Pile on a lot of organic, compostable material, and let nature take its course.
The latest bed-building method to turn gardeners’ heads is actually an ancient technique called hügelkultur. The German word, meaning “mound culture,” is usually pronounced “hoo-gull culture” in English-speaking gardening circles. It is one of many techniques associated with permaculture, a philosophy that seeks to understand, mimic and incorporate natural relationships and systems into the garden.
Hügelkultur differs from previously popularized no-till bed-building techniques in a few key ways:
1. Woody Base Material
Hügelkultur beds are ideally built with a base of logs or branches and prunings from woody shrubs. The larger the woody base material, the more self-sustaining you can expect the beds to be over time.
Hügelkultur beds can be huge. Building beds 6 feet tall or more with entire trees as base material is not uncommon. At this size, hügels can be used as growing space as well as windbreaks and will require little to no supplemental irrigation. However, hügels do not need to be enormous to be effective. This type of bed offers many advantages to the small-scale gardener, even when diminished to a more reasonable backyard size of 2 or 3 feet.
3. Angle of Bed Sides
While most no-till methods create relatively flat beds, permaculture expert Sepp Holzer advocates for a 45-degree (or steeper) angle on hügelkultur beds. In beds where the side angle is too shallow, he says the beds become compacted and the oxygen supply is decreased, which is detrimental to plant growth.
4. Long-Term Soil Fertility
Larger hunks of wood break down slowly, and their consistent decomposition provides long and even nutritional benefits to the soil and to the plants growing in the hügels.
5. Moisture Retention
As cellulose- and lignin-eating fungi act upon the woody base material, the logs and branches in the hügel break down into something like a sponge. This creates countless tiny air pockets and consistent moisture levels within the hügel. This combination is very conducive to plant root growth. Small hügels can go weeks without irrigation, while the largest ones can go entire summers without supplemental irrigation, even in dry climates.
Mound of Possibilities
Assess your site. Because this technique results in garden beds with a long-term soil fertility advantage, it’s best to spend some time thinking about how and where to locate your hügel before you start assembling.
Like any garden bed, you want to position your hügel where it will most benefit from the sun. Usually, this means building the bed so that it runs mostly north to south. Because hügels are mounded, not flat, beds built east to west will have one side always in shade. Unless you live in a very sunny climate and want to deliberately create a shaded, cooler microclimate, this isn’t ideal. Also, consider the prevailing wind direction and how the hügel can be buffered from strong winds.
Think about the slope of the ground where you will be building your bed and any moisture or water runoff issues that your garden has. Strategically placed hügels can soak up and hold excess water to good advantage, but you shouldn’t position them so that they create a barrier against the natural flow of water in your garden. If water runs against your hügel and pools, it can start to undermine your bed.
Feel free to be creative! A hügel can be made free-form and doesn’t have to be built as a rectangle. In fact, many hügels are built in a wide, open bowl-shape to capture the most energy and warmth from the sun.
Depending on the projected size of your hügel, you may need to start collecting woody waste material until you have built up quite a collection. Logs, branches, tree-trimmings, root balls and similar materials make the ideal base for a hügel, but work with what you have.
Untreated, unpainted, raw wood left over from building or construction projects may be incorporated into a hügelkultur. Wood chips can be used in place of logs or branches, but these will result in a more homogenous hügel with a much faster nitrogen “burn rate” and without the same long-term soil fertility advantages of a hügel made from larger pieces of wood.
Rotting wood is excellent for use in a hügel—in fact, the rotting of the wood is the magic behind this technique—but fresh-cut wood is fine, too. Just know that the results of the bed will improve as the wood breaks down over time, so don’t expect the best results in the first year if you start with green wood.
There are a few kinds of wood to avoid. According to Paul Wheaton, permaculture expert and founder of Permies.com and RichSoil.com, you should not use cedar, black locust, black cherry, black walnut or any treated wood in your hügelkultur bed.
Hügelkultur is an excellent, natural recycling technique, allowing woody waste to be converted into valuable growing space. For this reason, try not to buy fresh wood for your bed. If you don’t have appropriate materials on site, get creative. Call around to local tree-trimming companies, and ask if they could drop off some branches or scrap trimmings next time they are in your neighborhood. Maybe your city or town is taking down a tree that is interfering with power lines and would welcome help disposing of the wood.
Holzer suggests that you begin building your hügel by digging out a shallow trench, removing any turf from the area where you will place the bed and setting it aside. However, unless you are building your hügel on top of a particularly pernicious grass, such as Bermuda, this step is not essential and you can build your bed directly on top of the lawn. This is less work, and in most climates, the sod will break down into beautiful soil once covered with the raised bed.
(Note: An exception to this rule is for gardeners building hügelkultur beds in arid climates. In these areas, building the hügel within a swale can help to collect and trap precious moisture and groundwater within the bed.)
Lay your woody material in the area designated for the hügelkultur bed. If you have a variety of sizes of wood, try to place the larger pieces toward the bottom and center of the bed and work outward with smaller branches and organic debris so that your bed is stable.
After the woody framework is built, tamp it down to give it good contact with the ground (this is particularly important if you did not initially trench the area under your hügel). Now you need to cover up your wood. The simplest way is to dump soil right on top of your base material. Holzer suggests turning upside down the sod strips removed when trenching for the hügelkultur bed and covering the wood with those. A layer of straw, chicken-coop litter, leaf debris, kitchen compost or half-finished compost also works just fine. Hügels are flexible; use what you have to cover the wood in the bed.
You want the top layer of organic matter to fill in any large pockets between the wood and to cover the bed by several inches. This layer will settle into the woody base naturally, so don’t compact it or worry too much about small empty gaps within the base layer.
Lastly, add a layer of finished compost or topsoil. You can add as much as you have—a foot, a few inches or none at all. Adding more compost will give your hügel a more finished appearance, but this step is a matter of preference rather than necessity.
Build Your Garden
Your hügelkultur bed is now ready to plant. You can seed it immediately or transplant vegetable starts into the soil pockets within and around the bed.
When I built my first hügelkultur beds last year, I was pleasantly surprised to find that they held a soil temperature notably higher than my traditional raised beds. Very early last spring, when my traditional raised beds were 42 degrees F, my hügelkultur beds were 47 degrees Fahrenheit. A few weeks later in mid-spring, the soil in the hügelkultur beds was up to 78 degrees Fahrenheit, which is very warm for Seattle in April. Hügelkultur beds will typically be warmer than the surrounding soil for several years as the woody base material composts in place.
I watered my hügel only three times over the course of the summer (my traditional beds were watered twice a week), yet still saw excellent results and lush growth from the beans, squash, peppers, tomatoes, corn and various greens I seeded in that spring. I’ve only had one problem with the beds: They seem to be magnets for my flock of backyard hens, who are drawn to the huge worm populations living in and around the beds. They scratch things up terribly!
My own experiments with building and planting hügelkultur beds have convinced me that this technique is an easy way to reduce organic waste, build top-quality soil for free and grow great crops with less irrigation.
Get more gardening techniques from UrbanFarmOnline.com:
- The No-Soil Solution
- How to Make Organic Compost
- 7 Tips for Container Gardening
- Build a Rain Garden
- How to Start Vertical Gardening
About the Author: Seattle-based writer Erica Strauss covers urban homesteading, backyard chicken-keeping, edible gardening and more at Northwest Edible Life.