How to Build a Hugelkultur Raised Garden Bed

I was first introduced to hugelkultur garden beds when volunteering with Terra Commons a local non-profit that created edible forest gardens in people’s yards in Olympia, WA.  At a workparty we created 2 hugelkulturs out of old logs, sticks, leaves, and soil.  One was pretty long, maybe 30x6ft long and the other was a 6×6 herb spiral.  It was a lot of fun, working with friends piling up old rotting wood and fitting it in to a neat rectangle shape.  One of the places I lived in Olympia, had started out as a gravel parking lot, that had big trucks on it for years.  By the time I moved in they had transformed the space by building massive hugelkulturs.  It was amazing to see how drastically the mounds had completely transformed the landscape.  They had created hills, valleys and diverse micro-climates.  My friend that had built them said that they were not very productive–in terms of how the plants were growing on them–until the third year.

What is a hugelkultur?  A hugelkultur is a raised garden bed made out of woody material, in layers from big to small, topped with a minimal amount of soil to top it off. Hugelkultur garden beds go back hundreds of years to Eastern Europe and Germany.  Hugelkultur translates to “mound culture.”

Imagine a forest.  As branches and leaves fall to the ground they are broken down by microorganisms such as mushrooms and bugs.  As the leaves and sticks break down over time they release their nutrients back into the forest floor.  Imagine sticking your hand in a big old log in a forest on a hot summer dry.  Chances are the inside of the log is going to be moist compared to the ground under your feet.

Here are some reasons why hugelkulturs are so great:

1. They are a great way to use yard waste, tree prunings, grass clippings, etc. all from your own land.

2. They reduce waste, keeping organic materials out of landfills and reduce air pollution, offering an alternative to burning.

3. They can build up healthy soil on top of anything, even cement (although the land would benefit from cement removal first).

4. They retain moisture as the woody debris decomposes.  They are generally wetter than an only soil raised garden bed.

5. They improve drainage in hard compact soils.

6. They get hot from the decomposition process, keeping plants warmer during cold conditions.

7. They create a diverse community of beneficial microorganisms.

8. They are fun group projects!

You can add pretty much anything organic to a hugelkultur:

• Fallen trees
• Rotten logs
• Sticks, branches, twigs of all sizes
• Stumps
• Leaves, green or brown
• Christmas trees
• Brown cardboard (tape and staples removed, w/o glossy paint)
• Newspaper
• Kitchen scraps, coffee grounds, eggshells, tea bags
• Woodchips
• Grass clippings
• Straw, old hay
• Bark
• Organic clothes, rags or rugs
• Organic manure
• Urine, diluted 9 parts water to 1 part pee
• Compost, unfinished is okay
• Soil
• Anything else organic you can think of, get creative!

These are some things I would not add:

• No Cedar because it breaks down slowly and has anti fungal properties
• No Black Walnut, Black Locust, Black Cherry or other allelopathic plants that may discourage growth with their natural chemicals
• No treated wood because it is full of nasty chemicals that will not help create healthy plants and microorganisms
• No petroleum products like synthetic rugs, clothing, glossy paper, or waxed boxes
• No, or minimal weed seeds, unless you want them to grow

The basic idea is to layer and pack these materials into the shape you want your hugelkultur to be.  It can be as big or as small as you want.  The materials are layered with the biggest pieces (logs, branches, stumps) on the bottom and the smallest pieces (compost and soil) on the top.  The denser you can pack the materials the better, but if you are doing something on a large scale, just tossing everything together and crushing it should be enough.

Hugelkultur Workshop

When I was living south of Port Townsend on the Olympic Peninsula, WA interning at Sunfield Farm and Waldorf School, I was encouraged to help with a hugelkultur workshop sponsored by Jefferson County Public Works Solid Waste Department.  The idea was to source all the building materials from the farm, but seeing as the farm didn’t have too much woody debris lying around and I didn’t want to take from the forest, I ended up contacting landscapers and asking friends for wood from their land.  I managed to get a good deal donated for the workshop.  The workshop went great and we had a good turn out, taught a lot of people about what they could do with all their woody yard waste, which there is a lot of in Washington State.

Here is a step by step guide on how to build your very own hugelkultur:

Step 1. Choose a site.  Where would your land most benefit from a raised bed, what you plan on planting in the bed should dictate where you build it.  Think about sun, shade, wind, proximity to your house, relation to animals, etc…

Step 2. Gather materials.  The more the better because they reek down and sink over time.  A tall piled hugelkultur may shrink to half its size the next year as the wood decomposes and air spaces get filled in.

Step 3. Prepare your chosen site.  This is a good time to think about where you are going to get soil for the top, because if you don’t have a big pile of soil on hand, you may want to dig out the area where you are planning on building your bed.  Dig out the size of your bed, about 6-12in deep as save this soil to put on top at the end.  Digging a small trench helps maintain the shape of your bed and will aid in retaining moisture.  If you don’t need to dig out soil for the top, you can just build on top of the ground.

Step 4. Create a border.  I like to start with a border of thicker logs since they can help keep everything inside once you start adding smaller materials.  This is also a stylistic decision, whether you want your bed to be neat and tidy or a more natural looking mound that will blend in with the landscape.  I always thought it would be nice to add stumps on the corners that people could sit on or maybe line the edges with inoculated mushroom logs.

Step 5. After you have the border, you can begin to fill in the bottom layer with the biggest pieces you have collected.  Try to fill in as much open spaces as you can.

Step 6. Water each layer.  As you pile up each layer, it is good to get them wet with a hose, especially if you are in a dry climate.  As you build up keep adding moisture as you go.  This will encourage and quicken the beginning of the decomposition process.

Step 7. Keep adding layers.  As you build up, add smaller materials such as branches, sticks, woodchips and straw.  By working upwards with smaller materials you will supply nutrients to plants sooner than the big pieces on the bottom.  The materials will break down over time and release their nutrients as they do, thus it is good to have varied materials for the plant’s long term food source.  As you add the layers, be sure to pack them in tight, you can get on top and dance around on the bed just be careful your feet don’t fall in a crack!

Step 8. Add nitrogen.  As the wood below decomposes it will take nitrogen out of the soil.  Nitrogen is essential for plant growth, so to counter this effect and keep the decomposition from taking nitrogen from your plants, add extra nitrogen. Sources of nitrogen include animal products such as manure, bone meal, blood meal, feathers, fresh kitchen scraps, urine, hair, coffee grounds, fresh grass clippings.  Materials that are green or juicy generally have more nitrogen and things that are dry and brown have a lot of carbon.  Learning how to balance these two is a very important part of gardening.  Manure is probably the best source for nitrogen and different animals create different qualities of manure for different purposes.  I would put a lot of manure in, we didn’t have so much for the workshop but we could have used a full layer (maybe 2-4inches thick) of it mixed in to the entire bed.  Do your research on this as too much nitrogen can be harmful for plants and I am no expert on this.

Step 9. Add top soil and/or compost.  Add as much as you have, the more the better.  We put about 6-12 inches deep in most places.  You can get away with a minimal amount (1 inch thick) if that is all you have–one of the beauties of hugelkulturs is that they don’t need a lot of soil, because the wood will become soil over time.  Cover the bed with soil trying to keep it in the shape of the mound you created.  The more soil you add, the better your bed will do immediately.

We were lucky to have a tractor help us plop the soil on.

Step 10. Plant in it.  Hugelkultur beds can be planted right away.  You can sow seeds or transplant like you would anywhere else.  Another option is to let the bed decompose over winter and plant in the beginning of spring.

Here is a list of great things to plant in your hugelkultur bed:

Fruit trees, like apples, peaches, pears, cherries, figs, etc.

Perennial vegetables like artichokes, rhubarb, sorrel, salad burnet, bloody dock, jerusalem artichokes, lovage, marshmallow, good king henry and lots more (see perennialvegetables.org for a complete list).

Herbs, like sage, mint, catnip, mullein, thyme, oregano and so many more.

Berry bushes, like raspberries, gooseberries, currants, josta berries, strawberries, elderberries, blueberries, etc.

Vines, like kiwi or grape.

Don’t hesitate to try annuals too, I am just more of a perennial person myself.

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