What is Hugelkultur and How Does It Benefit the Permaculture Garden?

Hugelkultur, meaning "hill culture" in German, is an agricultural principle using plant and tree biomass to mimic woodland decomposition. Typically, large mounds of logs and plant material are layered directly on the ground and then covered with a layer of soil to make a steep-sided raised bed. Some Hugelkultur beds can reach 6 feet tall or more, though it is also possible to keep the height near ground level. Hugelkultur has been utilized for centuries in Germany and has recently found favor with the permaculture movement and organic gardeners due to its sustainability and low impact.

How Can Hugelkultur Benefit the Home Gardener?

As a Hugelkultur's biomass decomposes, it becomes porous and acts like a sponge, absorbing large quantities of water. This water is later released back into the soil on demand via capillary action. This process of water retention is so effective that it has even been used in desert gardens to decrease the need for irrigation. Each Hugelkultur bed can last 20 years or more.

Since Hugelkultur aims to mimic natural woodland decomposition, it is a great way to nurture beneficial microorganisms, nematodes and bacteria. In turn, these encourage the slow release of nutrients into the earth in a symbiotic relationship, eventually creating a fertile, loamy, self-irrigating soil.

The water-retention benefits of a Hugelkultur bed are normally apparent by its second year. By this point the tree biomass, which is the slowest to decompose, has had time to absorb and build up water reserves. After the second or third year, the bed may never need to be watered again.

Heat generated from the decomposition of the biomass can also warm the surrounding soil for several years, extending the growing season for gardeners in cooler climates.

Nitrogen Robbing

A concern that is often raised when discussing Hugelkultur is that the decomposing wood and other biomass is known to initially "steal," or lock up, plant-feeding nitrogen from the surrounding soil. While this could be a potential problem, it is worth remembering that Hugelkultur beds have been used effectively for centuries, and many people have reported no problems related to nitrogen locking. The logs are normally buried deep enough to not affect the fertility in the upper layers of soil.

Hugelkultur beds often include plant biomass that is less dense than the logs, so this normally decomposes more quickly, releasing nutrients into the soil. This process counteracts any nitrogen locking of the denser, slower-to-decompose logs. The small risk of initial nitrogen locking can be avoided by using partially rotted wood in the initial construction of the beds. If initial nitrogen locking does become a problem, this can be remedied by supplementing each bed with a nutrient-rich compost or a homemade organic liquid feed for the first year or two. After this time, the beds should become self-feeding. Still, it is worth reiterating that many Hugelkultur beds made with a shallow topsoil layer do not exhibit any significant nitrogen locking.

Aesthetically Adaptable

Hugelkultur beds are versatile and can be adapted to suit a wide range of gardening requirements. For those who do not wish to have large mounds in their garden, there is also the option of applying the Hugelkultur principles to smaller, traditional raised beds. By excavating the ground during initial construction, adding the biomass into the newly dug hole and then covering with soil, you can create a Hugelkultur bed to suit your needs. Some people use wood chips instead of whole logs, though these beds tend to decompose faster than the log-based ones. It should be noted that Hugelkultur beds do settle over time, so it is advisable to add some extra soil when constructing the bed, to counteract any settlement that may occur.

After initial construction, Hugelkultur beds are relatively easy to maintain, requiring only occasional mulching to help with weed suppression. Hugelkultur beds are suitable for most gardeners and they can be a great solution for locations where irrigation is difficult, or water is limited. They are also useful in gardens with compacted soil, or soil with low fertility.

As long as the principles of Hugelkultur are adhered to, this creative, adaptable, and sustainable permaculture solution should provide favorable growing conditions in any garden for many years to come.