“Hügelkultur is a composting process employing raised planting beds constructed on top of decaying wood debris and other compostable plant materials. The process helps to improve soil fertility, water retention, and soil warming, thus benefiting plants grown on or near such mounds,” as the wise persons behind wikipedia state.
That about says it all. Well maybe not quite all.
For a city lot, we have quite a few trees. They have been growing for quite a few years, including an Ash that is about 65 to 70 feet tall. Unfortunately, we have some issues with the location of the the trees. Four of our trees are so close to the house, that the roots are nibbling away at the foundation, and some of the branches threaten to take out the top floor in the next ice storm. Others that we have already trimmed or cut down, were blocking the light from getting to the back yard. We literally had dirt patches, where only fungus would grow.
Although I hate the idea of cutting down the trees and attacking nature in this way, I accepted that it had to be done. The nice thing to know is I will be using all the wood. It is not heading off to a land fill, nor is it being burned.
In the spring, we will be laying out our first hügels. We will be digging trenches about one foot deep, six feet wide and roughly 40 to 50 feet long, with two feet of walking space between each one. We will lay the logs, branches, twigs, leaves and any other decent compostable material we have in the trenches. They will be piled until they are about four feet high. We will then put the excavated earth on top of the logs, green side down. Finally we will plant seeds for more nitrogen fixing plants. We will do the last step, on day before an expected heavy rain. Why use tap water when the stuff falls from the sky?
Once that is complete, we hurry up and wait. Since we are using fresh logs, rather than old rotting trees, we need to kick start the process. During the first year of a tree rotting, it sucks up lots of nitrogen and water. Anything we plant at this time will be competing for the nitrogen in the soil. That is why we will start by planting nitrogen fixers. Plants, such as clover, that collect and store nitrogen in the root system. This will help kick start the rotting and decomposing process in the hügels.
In the spring the following year, we start planting! It may seem like a long time to wait, why not just get a bag of manure, spread it around and start planting? The answer comes down to time. A bag of manure will provide some nutrition, but depending on the source, it may also contain residual antibiotics, pesticides, and fertilizers that were spread on the animal feed or given to the animal itself. We do not want that, or the risk of it. We want to minimize if not eliminate harmful chemicals, including residual traces.
In the following years, we just watch things grow and harvest our crops. We estimate our trees will take between 25 and 50 years to fully decompose. As the trees decompose, they release their stored nutrients into the surrounding soil. We supplement by returning all our composting material to the hügels. This can be accomplished by composting in one location and spreading the young dirt, or by making compost tea and spreading that.
We will also minimize what we remove. When we harvest annuals, we will take the fruit and vegetables, leaving the plants to compost in place. Perennials, we will obviously just take the fruit and vegetables, leaving the plant in place. For plants such as lettuce, where we pretty much want the whole plant, we will let a few of them grow to seed and reseed themselves.
In a quick summary, here are the benefits we hope to gain by using hügels rather than more traditional flat gardens.
- Carbon sequestering: The trees we are cutting down, are being returned to the soil, storing not releasing the carbon to the atmosphere.
- Fertilizer: As the trees rot and decay over the next 25 to 50 years, they will infuse the ground with the nutrients they accumulated overt their life times.
- Water management: As the trees decompose they become sponges. When it rains, they suck up the excess moisture. In dry spells, they release their accumulated water reserves. Hoses not needed.
- Growing regions: The different contours provide many different planting zones. Strawberries, as an example, love sunlight on their leaves, but the like cool roots. Their berries are sweetest when they are planted on the north slope, so they get the sun, but the ground is in the shade.
- More land: We will also get more growing space. Flat ground six feet wide will rise up six feet, in effect doubling the surface area of the garden and in turn doubling our garden.
I hope that helps explain what a hügels is and why we have chosen to use them.