Every once in a while, I come across some new way to garden I was unaware of before. At the Hartford Flower and Garden Show a visitor asked what I knew about Hugelkultur, and I had to tell him “Nothing, tell me what you know.” There is always something new to learn, research and read about in all endeavors, but I especially love new gardening ways and tips. He offered what he knew, and I promised to find out more and pass it on.
Hugelkultur is a German word meaning hill culture; the process of planting a garden or plants over or near buried logs decaying below the surface. While the logs are composting below ground, they are holding moisture like a sponge which the plant roots can access. Nutrients are also released from the decaying wood and made available to surrounding plants. It is like planting your garden over your compost pile to feed the plants over a long period of time.
This centuries’ old way to garden is making a comeback with permaculture enthusiasts. It is a self-sustaining practice, replacing the nutrients which the gardeners remove when vegetables are removed from the garden. It is also thought of as forest gardening. Nobody fertilizes or feed the soil in the forests, but no one is removing the fallen leaves and dead wood; they just rot in place, helping the new seedlings to grow.
The size of the pile should be at least three feet wide and three feet deep or high. Piles can be made above ground is location is in a wet area, just cover the pile with soil several inches thick whether above or below ground. Over the years, a depression will develop as the material below decomposes. More soil can be added to raise the level for easier gardening. The composting process gives off some heat which rises through the layers to benefit the plants above, perhaps allowing a little bit earlier planting in the spring and some frost protection in the fall.
One word of caution on the species of log used; do not use black walnut as this species of tree releases a toxic chemical called juglone which inhibits plant growth. Juglone is present and active even in dead wood. Other species of wood will not produce juglone. Soft woods such as pine will rot more quickly and hard woods will take longer. Wood will decay more slowly underground where there is less oxygen than it would if sitting on top of the ground and exposed. Be sure any wood used is dead to prevent sprouting from the wood used. Species of wood that works best are alders, apple, aspen, birch, cottonwood, maple, oak, poplar, willow.
When the hugelkultur system is first getting started, the soil microbes will be using nitrogen from the soil in order to do their work of breaking down the wood and organic matter. The microbes will eventually return the nitrogen plus more nitrogen from the wood, into the pile. Adding a sprinkling of blood meal to the pile will feed the fungi and bacteria doing the decomposition getting them off to a strong start.