Hugelkultur inspired raised beds for the small suburban homestead

This spring one of our big homestead projects were permanent, raised, hugelkultur beds. Hugelkultur is a German practice of basically burying a whole tree in a garden bed. Generally it’s done by digging a shallow trench, putting in the cut up tree parts in there, and then burying them in a 6′ mound. It creates a large berm in which you plant. This is great for a big property, but it doesn’t work so well for small suburban lots like ours, so I had kind of ignored it until a peer in my Horticulture program showed me the hugelkultur raised bed he made. That’s when I started looking into it more.

Hugelkultur has a number of benefits. For one, the decomposing wood in the bed helps retain water so you have to water less. Dramatically less, by some accounts you don’t even need to water at all. Also, the decomposing wood can warm up the soil so you can extend your growing season a little, and adds a ton of beneficial bacteria, fungi, and other lifeforms (such as earthworms and beneficial nemotodes) to your soil. Finally, it adds a lot of organic material to the soil, creating rich soil over time. I mean, if you go to a website dedicated to hugelkultur, they’ll probably list more benefits, but that’s the basic gist of it. There is one downside, while all that wood is decomposing, it can rob the soil of nitrogen, but you remedy that by adding high nitrogen things to the pile, like compost, manure, or grass clippings. It seemed pretty simple, but I didn’t genuinely start considering it until we cut down a bunch of woody plants last year.

We had several shrubs and a tree die in the polar vortex Colorado experience in 2014, so we had to cut them all down in 2015. We also trimmed a significant amount of dead off of a tree in the neighboring yard that was hanging into our yard (the property is abandoned, so there were no homeowners to take care of the tree, not that the tree was well cared for when there was a person living there, but that’s a whole other story), and removed an evergreen bush that I just didn’t like (we replaced it with a serviceberry bush). When we did, we opened up an amazing spot with good sun where we could put permanent beds, but also landed ourselves with a big pile of logs and branches. Our first instinct was to burn them. We have a small fire pit and occasionally like to have bonfires in the summer, but this would be a lot of burning, and I couldn’t stand to think of all that carbon getting out into the atmosphere. That’s when I started thinking that maybe we should bury them. That’s when my plans for these beds started forming.

I suppose I could maybe call these more hugelkultur inspired beds than literal hugelkultur beds. They aren’t 6′ tall, and they aren’t the typical shape of a berm that most people think of when they think of hugelkultur. I’m also not sure I used quite as much wood as what is traditionally used, but I think they will work pretty well and still provide some level of the same benefits of a true hugelkultur bed. They fit nicely into our small yard and would please our HOA if they came to inspect them, so I’d say it’s a win. Also, we sequestered a good chunk of the carbon that was in those trees, putting them into the soil where it could be used by my plants, rather than burning them and putting that carbon into the atmosphere. Here’s how we did it.

The area had been totally mulched with rock by the previous owners, so the first thing we had to do was dig all of that up. As previously mentioned, digging up rock sucks a big fat one, but we got it done fairly quickly and were able to unload the rock fairly quickly by giving it away for free on Craigslist. The two people who came and got it were both using it for construction purposes, not as a decorative mulch. I hope this means that use of rock for decorative landscaping is at the end of it’s lifespan. This stuff sucks so bad.

Once that was done, Jeremy designed the beds and marked out where they would be using wooden stakes and string. The beds would be on a slope, so he put more effort into the design than what I could manage, but I promise I’ll interview him to get a run down of what went into designing these beds on a slope. Once the location of the beds were mapped out, we proceeded to dig the beds out. We started with the bed at the bottom of the slope, which was also going to be our biggest bed. I don’t know that I put much thought into picking that bed first, but as the project proceeded, I was really glad that I did, because each bed got progressively easier after that one. We piled the dirt we dug out in the space where the second bed would be. The idea was that once we put in the branches, then compost, then straw, we would then cover it with the soil we dug out and that would fill up the rest of the bed.

We dug the bed area out about 8″. I had originally wanted to do a foot deep, but digging clay soil is pretty tough, and I wimped out. I figured the wood frames Jeremy had built for the raised bed was tall enough. Speaking of the wood beds, we put a lot of research into picking the best material with which to build our raised bed. First Jeremy was thinking about treated wood that is commonly used for decking, because it wouldn’t rot and would be relatively cheap. I had heard that those could leach toxic junk into the soil, but Jeremy didn’t think it was a big deal until he went to the hardware store to buy it and noticed there were signs on the wood saying that it wasn’t intended for use in which it would come into contact with soil. So we scrapped that idea, and started looking into other options. We looked at cinder blocks, cedar planks, corrugated steel, and even reclaimed bleacher wood from a local industrial reclaim shop, but eventually settled on finding a non toxic coating for cheap pine boards. Our budget and our lack of free times played heavily into our decision making process. We found a wood treatment product online that was non toxic and vegetable based that said it would extend the life of our wood, and decided to give it a try. Jeremy applied it to the wood using a paint sprayer, and it turned our wood a subtle grey color.

So once the first bed was dug, Jeremy assembled the bed frame in the driveway, and then we carried it down to the hole and put it in place. Because this was the biggest bed, this was the heaviest frame. And because it was at the bottom of the hill, it was also furthest from our driveway, so we had to carry it the furthest. I was glad it was over with early. Everything from there was much easier. Jeremy put a lot of effort into making sure the frame was completely level and the perfect distance from our fence and the path that ran down the hill from our fence to our backyard. Part of it was just because he had a vision for how it would look and wanted to make sure it looked nice, Jeremy is a good craftsman and takes a great deal of pride in his work. But also, making sure the bed is level is important for making sure that drainage is good and that all the soil doesn’t roll out when it rains or something like that. Once the bed was level and secure in it’s spot, it was time to start filling it.

 

First we put in a layer of branches, stumps, and roots that came from the shrubs and trees we took out last year. We decided to focus on using branches and stumps rather than big logs because we had a lot more branches and roots and stumps than big logs, and because we do like to do an occasional bon fire, we figured we’d save the stuff that was more convenient to burn for that. I had read a lot of different things about whether or not it is okay to use evergreen wood in your hugelkultur bed, some argued that it would acidify the soil, others that it did nothing. The conclusion I came to was that maybe in places where soil acidity was a problem, using evergreen could be problematic, but here in Colorado the soil tends to be so alkaline that you could use it instead of baking soda to make a paper mache volcano erupt in a middle school science fair. A little pine would probably be good for it, after all, I grow strawberries under a spruce tree out front. I went ahead and used all the evergreen branches in the beds.

After the layer of branches, we put in some compost. My compost has long suffered from not having enough carbon, but I decided not to remedy it because I figured that high nitrogen compost would be a net benefit in a hugelkultur bed. Also, not all my compost is perfectly decomposed, but I figured that wouldn’t matter in a hugelkultur bed either.

On top of that, I put a bale of straw from last year’s straw bale gardens. This was probably more carbon, which might used up more nitrogen from the compost, but I needed to do something with the straw, and this seemed as good as anything else.

Finally, we started filling the bed back up with the soil we dug out of it, but it quickly became apparent that it would not be enough to fill it up. It was looking as if we would have to go buy some planters mix to top the beds off. When we started digging the second bed, we decided that rather than put that soil in the bed above it, as we did with the previous bed, we would put it into the first bed, to try and fill it further. This would also mean that we wouldn’t be digging this soil twice, as we had with the soil we dug out of the first bed. We would just put the soil from the third bed into the second, and the soil from the fourth bed into the third, and so on. However, even all the soil we dug out of the second bed was not enough to fill up the first. I decided we could probably stand to put more branches in the subsequent beds, but other than that, the process was essentially the same for each bed. Dig the hole, put the soil in the bed you did before it, set the frame, fill with branches, then compost, then straw, dig the next hole. There were 4 beds in total.

It took three yards of planters mix to fill the beds up the rest of the way! I was not expecting that at all. We put in two yards first, then let it sit for a week to see how much it would settle. It rained a few times during that week, if it hadn’t, we probably would have watered it to encourage further settling. After a week it settled some, and it took one more yard of planters mix to top them all off.

I suspect the nitrogen will likely be a little low in these beds, so I will probably have to fertilize every now and then. Also, as the wood decomposes, the beds will sink, so I will make adding compost a regular thing we do in these beds to help keep them full. The wood will probably decompose faster than a traditional hugel, because we stuck with branches instead of big logs. But I started planting in them immediately and expect them to be perfectly good raised beds, at the very least! I’ll report on my feelings on them as time goes on, of course, but there are the basics!

Have you heard of hugelkultur? Have you tried it on your homestead? Would you? Tell us about it in the comments!

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