Step 2 - Soil & Fill
Hugelkultur: Filling a Raised Bed with Wood
Hugelkultur is a German word for burying wood under your growing soil. In a deep raised bed it is mostly a cost-saving technique.
Janet H. - the hands-on owner behind Janet Media Group.
Published - last updated
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Hugelkultur -- literally mound culture -- means burying woody material under your growing soil. In a deep raised bed the practical version is straightforward: 4 to 6 inches of logs and branches at the bottom, well below the root zone, with everything else built on top.
It does three things. It displaces expensive fill, it holds water like a sponge once the wood has soaked, and it slowly releases nutrients over years as the wood breaks down.
Does it lock up nitrogen?
This is the standard objection and it is real, but it is a question of location. Wood breaking down consumes nitrogen at the interface between wood and soil. If that interface is in the root zone, your plants compete with the decomposers and go pale and stunted.
Keep the wood in the bottom few inches, below 10 to 12 inches of growing soil, and the competition happens somewhere roots are not. This is exactly the same reasoning that says wood chips are fine as mulch on the surface and bad dug into the top few inches.
Which wood
| Use | Avoid |
|---|---|
| Maple, birch, poplar, willow, fruit wood | Black walnut -- juglone inhibits tomatoes and others |
| Partly rotted logs (they soak up water faster) | Pressure-treated, painted or stained timber |
| Branches and prunings from your own garden | Cedar and redwood -- rot-resistant, so they do very little |
| Storm debris and untreated offcuts | Diseased wood, particularly from fungal-infected trees |
Partly rotted wood is better than fresh. It has already started breaking down, it absorbs water immediately rather than after a season, and it releases nutrients sooner.
Building it
- 1
Cardboard on the ground first
Smothers the grass and breaks down. Do this before any wood goes in.
- 2
Lay logs and branches, 4 to 6 inches
Pack them reasonably tightly and fill the gaps with smaller prunings. Large air voids cause uneven settling later.
- 3
Soak it thoroughly
Dry wood takes a long time to wet through and will pull moisture from the soil above until it does. Water it heavily before the next layer goes on.
- 4
Cover with leaves, clippings and spent soil
This intermediate layer fills gaps between the logs and starts the decomposition process at the wood surface.
- 5
Add the growing soil
A bulk blend up to about 12 inches below the rim, then 10 to 12 inches of good growing mix on top. That final layer is the one the crop uses.
Plan for the settling
A hugelkultur bed settles more than a conventionally filled one -- several inches in the first year is normal as the wood compacts and the leafy layers break down. Top up in spring with compost, and expect the bed to stabilize after a couple of seasons.
That annual top-up demand is, again, the argument for a compost bin. For the general method, see how to fill a raised garden bed; for the broader cost-saving approach, how to fill a raised bed cheaply.
What to buy
The products that fit the advice above, chosen by the process on our how we choose page. We have not hands-on tested them; specifications are the manufacturers’ own.
Quick picks
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 |  Top pickEspoma Organic Raised Bed MixPurpose-made raised bed mix, widely stocked | The simple bagged default | 8.7 | Check price on Amazon |
| 2 |  Charlie's CompostComposted poultry litter with mineral additions | A compost boost, not a fill | 8.4 | Check price on Amazon |
#ad We may earn a commission - prices are shown by Amazon, not by us
Scores are our own editorial judgment, formed from published specifications and independent sources. They are not aggregated customer ratings, and they are not the result of hands-on testing, which we do not currently do. See how we choose.
Common questions
What is hugelkultur in a raised bed?
Burying woody material -- logs, branches, prunings -- beneath the growing soil. In a raised bed that means 4 to 6 inches of wood at the bottom, below 10 to 12 inches of soil. It displaces expensive fill, holds water, and releases nutrients slowly as it decays.
Does wood in a raised bed steal nitrogen from plants?
Only where wood and roots meet. Decomposers consume nitrogen at that interface, so wood in the growing layer starves the crop. Wood in the bottom few inches, below 10 to 12 inches of soil, keeps that interface away from the roots.
What wood should not go in a raised bed?
Black walnut, which contains juglone and inhibits tomatoes and several other crops. Also avoid pressure-treated, painted or stained timber, diseased wood, and rot-resistant species like cedar and redwood, which break down too slowly to contribute anything.
How much does a hugelkultur bed sink?
Several inches in the first year is normal, more than a conventionally filled bed, as the wood compacts and the leafy layers break down. Top up with compost each spring. Beds generally stabilize after two or three seasons.
Sources
Factual claims on this page are backed by the published sources below, and product specifications are the manufacturers’ own. Where a figure is not published, we say so rather than estimating it.