|Just Beginning to build a Hugelkultur "edge"|
Hugelkultur beds are an amazingly simple concept, used across the pond for ages but fairly new in the US. The beds are made by piling partially-rotted trees, limbs, trunks, leaves and other garden woody waste thickly, and covering it with mulch and soil. The name comes from the German hügelkultur, which translates as "hill culture".
The layers break down slowly, creating rich humus over several years. As the years pass, the deep soil of the raised bed becomes incredibly rich and loaded with soil life. As the wood shrinks, it makes more tiny air pockets - so your hugelkultur bed becomes self tilling. The first few years, the composting process will slightly warm the soil, giving a slightly longer growing season in temperate and cold climates. (Source)
There are many designs and methods and they all work; the actual design is usually based on the particular needs in the garden. Some are just a foot or so deep and 2-3 feet wide, while some are several feet deep and wide. Some folks dig a pit in the ground, add the waste woody material, and use the removed soil to cover the pile. Some just start directly on the ground, and then cover with mulch and soil. I've even seen photos of hugelkultur beds using enormous tree trunks piled 6 feet high and 40 feet long. Here's a link to a photo illustration of the general concept.
What the rotting wood does is sequester moisture like a sponge in the soil, negating most if not all the need to water plants in a hugelkultur bed. As the woody waste decomposes, the humus created feeds soil life, which in turn feed the plants that feed us.
While my new planting area is much too large for me to physically tackle as one enormous hugelkultur bed, I decided there are enough benefits to make what I'm calling a "half hugel" or a "hugel edge". The area I am sheet mulching is on a gentle slope down to the creek, and I am using hugelkulture concepts to build up the lower edge which runs parallel to the creek and perpendicular to the slope.
I will continue to post on this 'half hugel' as I get more put in place. In the meantime, here's a link to building a hugelkultur bed of your own, and here's another link showing how they age, with photos of real beds being built at the bottom of the page.