The latest technique to turn gardeners’ heads is an ancient bed-building method called hugelkultur. Usually pronounced “hoo-gull culture,” this technique’s name comes from the German word meaning “mound multure.”
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What is hugelkultur?
According to permaculture expert Paul Wheaton:
"Hugelkultur is nothing more than making raised garden beds filled with rotten wood. This makes for raised garden beds loaded with organic material, nutrients, air pockets for the roots of what you plant, etc. As the years pass, the deep soil of your raised garden bed becomes incredibly rich and loaded with soil life."
Hugelkultur is similar to lasagna gardening, the Ruth Stout system and sheet mulching. Like these, it creates a raised-bed garden rich in organic matter that feeds the soil so it gets better with time. However, hugelkultur differs from previously popularized bed building techniques in a few key ways:
1. Woody base
Uniquely, hugulkultur beds depend on a “foundation” of wood. Tree trimmings, logs, clean scrap lumber or even entire felled trees can form the base of a hugelkultur bed. The very slow breakdown of this woody base keeps soil fertility and moisture retention strong over years or decades.
Hugelkultur beds can be huge. Many of the most well known advocates of this bed building method, including Paul Wheaton and Sepp Holzer, routinely create hugelkultur beds 6-feet-tall or more. In exceptional cases, beds are built up over entire felled trees. These grand hugels can transform a landscape, double as windbreaks and act as water-channeling berms. However, massive scale beds aren't necessary to get many of hugelkultur's benefits. My own hugel beds started at a modest 18-inches tall, and have settled to about a foot tall.
3. Steeply sloped sides
Along with their enormous potential size, hugulkultur beds differ in featuring much steeper sides than most other lasagna-bed type approaches. Keeping the sides sloped at about 45 degrees is believed to reduce soil compaction over time and increase soil oxygenation.
4. Moisture retention
As the wood base of a hugelkultur bed slowly breaks down, cellulose and lignin eating fungi slowly consume the woody base material, transforming the logs and branches in the hugel into something like a sponge filled with countless tiny air pockets. The unique texture of the decomposed wood supports consistent moisture levels that encourage strong plant root growth. Even in dry climates, the smallest of hugels can go weeks without supplemental irrigation while the largest ones can support lush growth through an entire summer without additional water.
Adding a hugelkultur bed to your garden
Much of Hugelkultur’s rising popularity has to do with its association with permaculture, an increasingly popular gardening philosophy that seeks to understand, mimic and incorporate natural relationships and systems into the garden. If you are thinking of incorporating hugelkultur into your garden, take some time to think about the whole system of your garden, and consider how this kind of bed will impact what you already have. Hugelkultur is a long-term soil building technique, and the beds you build will get better for many years. The more considered your approach at the beginning, the happier you will be with your hugelkultur beds.
Key considerations when siting a hugel
Some hugul beds are built running east-west so that the mounded bed has a variety of microclimates — a hot and sunny south side and a cooler and shaded north side — to take advantage of. If you plan on using your hugel for vegetable production, it can make sense to run the bed north-south so your crops receive more even light exposure.
Look at the water flow in your garden and pinpoint both the low lying, moist or mucky areas and the areas that drain like a sieve. Positioned strategically, a sponge-like hugel can soak up or redirect excess water, but too much water, pooling or flowing along the side of the bed, can undermine the bed’s structure.
A hugel bed, particularly a large one, will modify the air-flow in your yard.
- Where the dominant winds come from in your climate
- What areas might benefit from a wind block in your garden
- How a large mound in your yard might modify air flow and what the impact of that might be
- How a hugel might change existing frost pockets and microclimates
- And what you plan to grow in your hugel, because crops planted on the top will have to cope with considerable wind if the hugel is in an exposed, windy location.
Hugels are not typically framed in or edged and tend to be more freeform in their look and design. So, a hugel needn't to be conventionally rectilinear! Consider gentle arcs, open bowls, or whatever shape the considerations of light, water, wind, and existing terrain suggest.
If termites are an issue in your area, avoid building a hugel bed too close to your home. Although I've never had an issue with termites, it's best to be prudent.
What kind of wood?
Start preparing to build your hugel while you’re still considering the questions of siting it. A large hugel bed can take a considerable quantity of wood. If you know you want to add hugelkultur into your garden, start saving logs, cut branches, tree trimmings and other garden wood even if you aren’t yet quite sure of where they’ll end up. Some woods contain natural chemical agents that make them extremely slow to break down and tend to suppress plant growth.
For that reason, avoid:
- Black locust
- Black cherry
- Black walnut
Any wood that is treated, including pressure-treated wood, railroad ties, pallets or painted/stained wood, should not be used. Clean, untreated construction or demolition scrap wood is OK. Just make sure any wood you use is untreaded and unpainted and make sure to pull out any metal hardware.
Wood chips can be used too, but will result in a more homogenous hugel. This will burn nitrogen faster and not offer the same longevity of fertility that a classic hugel full of larger logs and timbers would. If you lack sources for wood, don’t run out to the local big-box store and buy a bunch of dimension lumber to bury in your garden. Hugulkultur is too good of a recycling technique for that!
Building and maintaining
Building a hugelkultur bed is as simple as laying down your scrap wood — freshly cut, well-rotted, or anything in between — and covering it with soil. That's it! Everything else is just optional. If your wood is freshly cut, a deeper layer of good quality soil atop the wood will make this year's garden grow better. If your wood is well decomposed already, you can use less soil.
Try to fully cover the woody base material. If the logs stick up above the soil level, it takes them longer to break down. When I built my hugelkultur beds, I used strips of upside-down sod, half-composted straw, the bits from the compost pile that weren't quite ready, and anything else I could find laying around my yard to cover up the wood. Then, I covered the entire structure with a few inches of finished compost.
Maintaining hugels is mostly a question of appearance. If, as they break down they slump, you may want to top dress them with additional compost or mulch. Don't till, turn or aggressively dig the beds — let the soil microbiology attracted by all that rotting wood keep the tilth of the beds lovely. My hugels continue to be some of my best performing and most fertile beds! They are a gardening gift that keeps on giving.