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.
I think a sunken hugelkultur bed would be fine with wood buried at the bottom of a sunken bed to perhaps hold moisture longer in that strata. It would have to be within the first 24 inches of soil as most annual veggies don't have roots that get much deeper than that - in fact most annuals are very shallow rooted (6-12").
I would also still mulch on top with straw to promote the bacterial growth in the soil which herbaceous plants prefer. Mulching will keep as much moisture in the soil as the wood buried within it and is way easier to apply.
It would be interesting to do an experiment of side-by-side sunken beds:
--Control bed - sunken, no buried wood, no mulch
--Bed 1 - sunken, buried wood, no mulch
--Bed 2 - sunken, no buried wood, mulched
--Bed 3 - sunken, buried wood AND mulched
Use the same exposure, amendments, amount of water and plant the same crops in all beds - see which performs the best.
Wish I had the room to do this. Probably take 3-5 years for the results to become apparent as the wood breaks down.
Puzzling things out keeps me very entertained!
Passion vine - good idea! Also some herbs like epizote (essentially a shrub). In fact I think that a lot of Mediterranean herbs are deeper rooted now that I ponder this... Perhaps some of the more herb-y folks can weigh in on this?
Actually carrots will put down roots to five feet (the hairlike roots, not the main root consumed) if the soil is friable enough to permit penetration and sufficent water and oxygen is available to support its growth. Robert Kourik's Roots Demystified lists a great number of vegetable roots found to grow down and out always if the opportunity presents itself.
Thanks for the awesome reference, Powell.
1. R U FN me!!!! I sure have seen an awful lot of primary canopy trees drawn planted on hügelkultur diagrams, including your link.
2. I am not surprised desert may not be a good place for it, figuring it would take at least three times as long to decompose. Also not as easy to get a lot of logs here.
3. Sunken beds, I could see a garden bed. 6"of top soil and wood underneath for 12" below. Initial garden watering would assist breakdown below. I could see sunken beds where rooftop rain gutters empty into the yard. Eventually that would be a great sponge and the initial water would speed up breakdown.
One thing, bacterial are not very important in the initial breakdown of wood. Fungi are responsible for that. Bacterial break the sugars down after fungal cellulases break the cellulose down.
Yep - definitely funguseses (yeah - I know it's "fungi" but "fuguseses" is more fun to say) break down wood. I was suggesting straw as a top layer mulch as a more beneficial interaction with herbaceous plants.
Regarding trees on hugel mounds - I always wondered about that but thought there must be some key piece of information I was missing. Turns out the other folks were missing the key information.
Along this line, I have a huge Chinaberry tree that needs to come down. There is no redeeming quality to this tree except shade. Because we had to build up the patio around it (to shed water away from house), we built basically a well around it. So it is surrounded by a cement block stuccoed over wall about 4' deep and 8' round. I thought of doing a hugelkultu herb bed in this well with the wood from the chinaberry. It may not be possible to take the stump out. The chinaberry is a terribly messy tree, shedding berries that are like walking on marbles, and will replicate it self easier then bermuda grass. Any thoughts on this?
So if I'm reading this right, you already have what amounts to a circular area around the tree that could function as a raised bed - right?
Can you reach across the well to the middle by standing on either side? That would be my indicator of what to plant there. If you can't reach the middle - plant in perennial plants, possibly a nectary for native pollinators. If you CAN reach the middle, plant something you can harvest from.
Were you thinking of filling the "well" with the chopped up parts of the tree? Will any buried berries sprout and menace the bed later on? If so, can you remove most of the berries so this isn't a problem?
I think it's worth experimenting with (and documenting!). Below are a few ideas off the top of my head. If you can't get the stump out, it could act as part of the hugelbed itself. The stump could be modified in several ways:
--leave it tall and use it as the center post to support twine or wire for climbing plants
--cut it shorter and grow a basin of succulents on top of it, drill holes in the side for solitary bee habitat
--cut it about level with the surrounding wall and see if you can hollow it out a bit and drill some holes in the side - it can be used as a wooden olla that would degrade over time.
I think there could be all sorts of clever things you could do with this. "Working with what you've got" is a key permaculture principle.
Do you have some pictures of the way it looks now?
THose are great ideas Jennifer. Thank you so much. Do believe I can reach middle. I will try and post photo. Having trouble uploading my IPhone photos into these discussions. Not sure why.
An easy way to get rid of a stump, if you are patient, is to decompose it with saltpeter, i.e. potassium nitrate.
Drill several 1" dia holes down into the core of the stump. Dissolve 1 lb of potassium nitrate in about 2 qts of hot water and fill the holes. Put a few inches of dirt on top and keep it moist. The stump ought to disappear in a year or so.
Planting a garden on top of it will speed the decomposition.