For those of you who don't know what Hugelkultur is, it is basically a raised bed with woody materials (logs, branches) at its core covered with sod. It is then planted out with food crops and some people say you can plant trees on them as well (as shown in the drawings to the right).
The premise behind hugelkultur is that the bed simultaneously holds moisture in the wood while still being "well drained" because it is raised. Also, this moisture will break down the logs and branches, providing a rich habitat for soil microbes an promote healthy root growth.
For a long time I was mystified by the statement that huglekultur "has been demonstrated to work in deserts as well as backyards".
How - I wondered?
This seems to be the antithesis of what we want to do in a "desert" - expose more surface area to extreme heat and evaporation. Plus, we want our beds to harvest water, not shed it.
Then there's the issue of having sufficient moisture to even cause the woody core of a hugelkultur to decompose. Most things will desiccate here before they decompose simply because of our heat and high evaporation rates. The only way I could really see this working is with sunken beds with wood in the bottom - something that I have inadvertently done in the past when digging the swale for my urban orchard - I just tossed some branches in the bottom of the swale - this was way before I ever heard the word "hugelkultur".
So this week at permies.com, Zach Weiss, Sepp Holzer's protégé, was answering questions on Sepp's methods. Sepp is credited as the inventor of hugelkultur. I took the opportunity to get the "expert's opinion" to see if I was missing out on some critical information regarding hugelkultur in hot, drylands like ours. You can see the conversation here: http://www.permies.com/t/37601/sepp-holzer/Hugles-HOT-Drylands
Basically I shared my concerns about the appropriateness of hugelkultur in our climate. Here are Zach's responses:
"You are right on the money with your sunken hugelbeds, we do indeed make them as depressions in the ground when working in dry lands or with sandy soil. The wood attracts the moisture and stores it in the depression. Kind of a pot-hole garden with wood in the bottom to help retain the moisture.
As I was just posting in another thread, Hugelkultur is treated like a one size fits all solution and that is just not the case. Most of the places I visit with Sepp he does not recommend any Hugelkultur. Often times the landowner even wants Hugelkultur and Sepp says that it just doesn't make sense anywhere on their land. It's all about the resources that you have available and working with them to the best of your ability."
And in answer to me posting about my experiences with my urban orchard sinking over time as the wood decays, he responds:
"Hugelkultur is often confused as a good system for growing trees, this is most certainly not the case. As the wood decomposes the tree roots will destabilize causing problems for the future. I've seen a lot of people that want to use Hugelkultur like swales but this is not how Sepp uses them. Hugelkulturs are for annuals and small perennials such as berry bushes etc. They can be used as a nursery space for trees but are not a long term tree growing system."
It was great to get answers right from someone who works side-by-side with the inventor of hugelkultur.
So in reality - no - traditional mounded hugelkultur is not appropriate for hot drylands such as ours.
It is also not an appropriate system for growing trees (even though the article referenced above and the images show a tree growing on a hugel) no matter if it is an aboveground mounded hugelkultur or a dryland sunken hugelbed.
While it may not be an appropriate system for "civilized" trees, in wild forests a hugelkultur scenario is very common. It's called "nurse logs".
In the Pacific northwest, home to giant trees, you can find rows of Douglas Fir, hemlock and other varieties that started by growing on a fallen tree. The rotting wood provides nutrients and moisture. In California there are forests with sequoias on nurse logs.
You would think that a 4 to 6 foot diameter log, rotting away after 200 years ought to leave a big hole and destabilize the trees growing on it. But that doesn't happen.
I have also read about a re-foresting system in desert-fied Africa that uses wood buried in shallow pits. The wood attracts termites which bring moisture up from the ground. They also dig tunnels that aerate and provide water channels. After a few years, a tree is planted in the pit which has become fertile and friable.
Brian - fascinating info - do you have a link to the wood/termite info?
No, sorry. It was about 2 years ago.
The story was about a man, who about 25 years ago, began to work on a 25 hectare tract that was desert. He began by digging a grid of shallow pits, connected by trenches to collect rain. The rain fall in the area was about 10" to 12" per year. In the pits he buried wood and then added some manure to attract insects. After a few years he began to plant trees and bushes. Over time, he added a variety of understory plants for diversity.
Now, the forest is fully grown and thriving. The unfortunate part of the story is that the forest is on community owned land and the council decided that now that the forest is valuable, they will cut it down and sell the wood. He is living on the land and will lose his house.