(This is the final piece of a three part series on preparing a new organic garden bed: double digging, the garden lasagna, and hugelkultur. At the end of this piece is a segment on combining these 3 ‘start a new garden’ methods.)
Hugelkultur is a very old method from eastern Europe that involves burying wood to create good soils. (I just heard the “Stop! Nitrogen Thief!” alarms go off for some of you. I’ll get to that, I promise.)
The gist of it: throw some rotting logs (wondering which wood is good wood? That’s coming right up), cover the logs with some dirt, plant the dirt.
The “why is this so awesome?” theory runs like this: the wood breaks down, creating rich, nutritious soil for the plants on top. As it breaks down, it leaves little air spaces in the soil, which the soil food web really appreciates. While it still exists, it acts as an amazing sponge, absorbing and releasing so much water that, after a year of getting started, many hugelkultur beds do not have to be irrigated or otherwise watered at all for half a decade.
The Diamonds are in the Details
For instance, how much dirt on top? Add in dirt in and around all the logs, then about 4 or 5 inches on top. If you leave big air pockets in amongst the logs, the first rain will take your topsoil down, and you’ll have to add more. Just tell the neighbors you meant to do that as you add more dirt on top again.
Really, though, it’s not the dirt. The crucial detail is the stack of wood. You can stack it low and flat (homeowners associations do not generally freak out over anything less than 30 inches (75 cm), and under 18 (50 cm) should be totally fair game. The most impressive “I never have to water and I live in the middle of Death Valley” types of stories often involve very tall stacks: 6 feet or so. I do not get the impression these are very wide stacks, and it’s possible that the solar orientation of these hugelkultur superbeds is important, but I don’t know exactly how yet. I’ll report back when I find out more.
But the stack itself is secondary to the actual wood that is stacked. If you are standing there with a freshly cut up tree that came down in last week’s storm, well, that’s not the wood you want. Start a new firewood pile with that on the bottom, then move what’s left of previous firewood piles (sorry, chipmunks) on top of your fresh green wood until you get to the questionable stuff.
Firewood should not crumble. Toss that in the hugelkultur pile. Firewood should also not have a little “give” to it. Toss that in the pile too. Good firewood does not typically have thriving mushroom and lichen colonies on it. On the other hand, those are great for soil building, so into the hugelkultur wood pile they go.
Other great sources of wood include your garden pruning brash pile. Wood from an old pallet that used to haul food to grocery stores in the US? That’s a good source. Wood from a pallet that possibly hauled chemicals? Skip it. Which brings me to this important detail:
Are There Woods to Avoid for Hugelkultur?
In general, almost all wood is good, but there are a few less, ahem, ‘cooperative’ species out there.
Woods that don’t break down, like cedar and black locust, get cumbersome in the garden. Black locust takes forever to start rotting, hence its popularity as a fence post material. Use it to edge your garden, or save it to burn when the power goes out in the winter- it’s a distinctly hotter burning wood than many others. Cedar has lots of oils in it and is a popular clothes chest material. It’s not going to breakdown fast, and those oils might be problematic for other plants.
Other woods, like camphor, black cherry, and black walnut, give off natural toxins to intentionally thwart other kinds of plants from growing too near them. You’ll want to either let these age a little extra, or put them in small pieces near the bottom of the pile.
Some folks worry about pine and fir trees too, due to the tannins, and yet I never see worries about oaks… I’m thinking this is where biodiversity in your garden comes in handy: just know that tannins will thwart the initial break down, and then will lower the pH (acidify the soil) for a while once they start leaching out. I don’t see a problem, I see a blueberry bed.
Willow logs will get you willow trees. Oops! Forsythia branches become forsythia shrubs pretty easy too: bury them deeeeeeeeeep.
Not sure what you’ve got? Feel free to load a photo below and see what the collective intelligence yields.
The Best of All Worlds:
Clear off the sod.
Use a pitchfork to loosen the soil a bit.
Throw down a thinnish layer of sticks and branches, leaving a foot or so border inside the bed unless you are doing a raised bed and have something to hold the height.
Garnish the wood with raw-ish compost (things what’s still identify-able), then throw on the sod you yanked off, green side down.
Layer leaves and other more composted stuff on top, filling in the border now too.
Cover that with a layer of newspapers and straw. Hose it down and then cover with a tarp for a month or two. Not only will you be rewarded with a bed of excellent soil in the spring from the lasagna gardening method, but thanks to the hugelkultur element, the garden bed you build will continue to improve its ability to nuture your plants for several years to come.