I first came across the term “hügelkultur” during an internet search on a gardening topic. This time, for once, my interest wasn’t sparked by a book. Basically, it involves growing vegetables on a compost heap with a base formed by a pile of logs. The idea is an interesting one, although I should stress that I have no personal knowledge of how well it works, as I have never seen one in action and it isn’t suitable for my own garden. Although frequently referred to as an ‘ancient technique’ in Europe there seem to be no references to either documentary or archaeological evidence for hugelkultur earlier than 1962. If anybody has any such references, I would be interested to hear them.

The word ‘hügelkultur’ is German for ‘mound cultivation’. It refers to building a raised bed on a base of logs, filled in with small twigs and bark, and covered with layers of straw, compost, grass clippings, dead leaves, chicken bedding etc and finally topsoil, in which you plant your vegetables. You can either build it freestanding i.e. completely above ground level, or sunk in a trench, or partly sunk. Some are gently sloping, some have almost vertical sides. As the logs rot and the various layers of leaves etc. compost down, a rich soil is produced. The porous logs retain moisture efficiently so the bed needs less watering than conventional beds, but it doesn’t become waterlogged. The slowly decomposing organic matter provides a slow release supply of nutrients. It doesn’t need digging over, so the soil structure remains undisturbed and it is expected to be rich in soil bacteria, fungal mycelia etc. It’s a good way to recycle organic waste into compost, and it is very much part of the permaculture movement, in that it is supposed to take care of itself and produce food for years. 

It is generally admitted to have some disadvantages. A certain amount of heavy labour is needed to set up, digging up the turf and moving logs into position, and you need to leave it for a year or so to become established. It doesn’t last forever and needs to be rebuilt entirely after five or six years. The bed slowly subsides as the compost material rots down, so planting fruit trees and bushes on top is not really practical. You need a source of logs (bark chippings alone won’t do) and a good deal of compostable materials to start it off with. Areas like Orkney and Shetland, with very few trees would have a problem. I am not sure that driftwood well-soaked with salt, or conifers full of resin, would really make a good base for a compost heap.  Holes will appear as the underlying logs rot down, which will need to be filled in with small stuff. It is also said to be an attractive habitat for rats. And you need a large enough plot of land. There is something scientific about wood needing extra nitrogen as it starts to rot; I have no idea whether this is really likely to have a significant effect in a garden bed or whether it is of purely academic interest.

Not everybody supports the method. An article written by an urban horticulturist and associate professor at Washington State University argues that ordinary raised beds are a better option and that the logs would be better used on the surface, as ‘nurse logs’ for wildlife, standing around the garden, or made into chippings for mulches.

An interesting side effect of my researches on this particular topic was that it brought my attention to the way my preferred search engine works and its AI summary is produced. My background research this time relied entirely on the internet, since the method doesn’t appear in any of the books I have got hold of. At one point I noticed that the sites that usually appear when I search on gardening topics, such as the RHS, Henry Doubleday, and various sites run by universities or botanic gardens, did not come up this time. Even Wikipedia was only on the second page. Instead, I got hardly anything except blogs from ‘alternative’ groups or individuals. I have no objection to druids and some of them did look practical, but I like to have a more orthodox point of view as well. When I did find Wiki and some of the blogs dealing with the disadvantages of hügelkultur, they stated that there have been no properly-designed scientific studies on whether it actually works.

I asked about how AI works at present, and it turns out that it relies on the sites which come up most frequently and which attract the attention of search engines most efficiently. It has no way at the moment to assess the reliability or the academic standards of its sources. The AI designers are well aware of this, and you can find out about it if you ask, but it is not immediately obvious to the casual user, or at least not to one of my age. In some ways this can be a good way of avoiding censorship on the internet, and it hardly matters if you are building a raised bed on top of a log pile, but it does mean that I would not like to bet on how well this technique works without trying it myself or visiting a garden where it has been used.

So, am I going to try building myself a hügel? No. It sounds as if it might be suitable for some environments, but Orkney has (a) an abundance of fertile agricultural soil and (b) a serious lack of trees. And I only have a small garden. I shall stick to tiny raised beds and containers and composting my kitchen waste. But I would like to see one in action.