A hugelkultur bed conserves water—a godsend in drought-stricken California.
The base of a hugelkultur raised bed contains a layer of dead logs and branches—organic material that, in the old days, I would have tossed into my yard waste bin for my city’s green waste truck to pick up and convert into mulch. Now I know that this organic material is good for the soil and helps to create a natural system for fertility and water retention, so I don’t throw it away anymore.
Why spend resources to have someone else turn these items into mulch when it would be more beneficial to keep them and let the bugs and microbes do the work of breaking them down?
What is Hugelkultur?
This word, which sounds funny, is actually German for “hill mound”. In its original form, a small pit would be dug and filled with rotting wood, gradually creating a long, narrow mound. On top of the logs, dirt would be piled, creating a tall, long structure that has much more planting space than a flat garden bed.
At first, the logs make the bed thicker. Over time, as they decompose, the hill becomes lower, and the rotted logs inside hold more moisture. If the bed is kept full, there is hardly any erosion of the soil, and it creates its own small ecosystem.
Most people who use raised garden beds simply want to have enough potting mix to create level beds, rather than using the more traditional hill mound structure.
Hugelkultur raised beds are a combination of wood and other materials like grass clippings, food scraps, and coffee grounds, which decompose quickly. The tops of the beds are covered with a preferred growing blend.
This method allows you to reduce the amount of material needed to fill your hugelbeds by utilizing permaculture techniques. At the same time, you can reduce the amount of woody material, such as branches and logs, that you might have lying around. If done correctly, the hugelkultur portion of your bed should be free of charge, saving you money.
Benefits and Drawbacks of Hugelkultur Beds
A lot of different benefits have been ascribed to hugelkultur beds online. Let’s list just a few of the most common:
- reduces watering frequency
- can use up waste wood or prevent it from needing to be burned in a burn pile
- increases the surface area of your garden beds
- may generate heat as the wood decomposes
- is an inexpensive way to create a tall garden bed
Everything listed above has both positive and negative aspects.
While a hugelkutur bed may help reduce the amount of watering needed, most of the benefits associated with water retention will not be realized until the wood starts to rot and becomes sponge-like. This process can take years when starting with large logs.
You probably won’t have easy access to waste wood unless you have a lot of trees on your property, live in a forest, or live close to orchards. If you need wood, you’ll likely have to find and buy it yourself. You can find large logs, but they may be too big for what you need and you’d have to use a log splitter to make them smaller. A lot of people buy a cord of firewood, but that might not be the best option if you’re trying to save money.
If you don’t want to build mounds that rise above your raised bed walls, you won’t have the same increased surface space, and in fact, may have no increases in space at all.
Most raised beds get warm earlier in the spring than an in-ground bed would, so there’s no need for the extra warmth. Wood is full of carbon and doesn’t release much heat as it breaks down. Nitrogen-rich materials release heat as they decompose, however.
What are the benefits of building a hugelkultur garden bed?
In my experience, the real benefits of a hugelkultur raised bed are as follows:
- Great way to use up branches, small logs, wood chips, scrap lumber, and virtually any other woody material you have
- Will in time act as a water reservoir at the bottom of the bed
- Can be extremely cost-effective to create
- Adds an abundance of organic matter to your soil
- Definitely reduces the amount of soil you’ll need to start your beds
- Reduces compaction and shrinkage in your raised beds
This more realistically depicts how hugelkultur would work in a raised bed setting. It won’t create miracles, especially when it’s brand new… However, over time, the advantages will be much greater than the disadvantages.
How To Layer Hugelkultur Raised Beds
After understanding what hugelkultur is and some of its pros and cons, let’s discuss the correct way to construct a hugelkultur raised bed.
Framing It Properly
While a wooden frame is possible, it is important to note that the goal of a hugelkultur system is to decompose the wood in the bed. Additionally, the wooden walls may also be at risk. If opting for a wooden frame, be prepared to replace the side walls as necessary. It is best to choose woods that decompose slowly, like cedar, even though they may be more expensive.
Brick, concrete blocks, and stone can also be used to create walls for your beds, but they will be much thicker, which may reduce the workable size of your bed.
Start At The Bottom
One advantage of a hugelkultur bed is that you can use some of the soil that is already in your yard. If you have good-quality soil, this is a great way to get the most out of your own topsoil while still raising the height up to a more manageable level!
If you want to build a raised garden bed using this method, dig out a couple of inches of the surface-level soil in the area your bed will be in. Set this soil on a tarp and put it to the side, you’ll use it later. Leave some hard-packed dirt to support the sides of the bed or bury some bricks under the walls of the bed to support them and prevent the bed from sinking down.
Once you’ve prepared a shallow trench in your bed, fill the bottom couple of inches with green waste. This includes trimmings from your garden, grass clippings, fresh manure, compost (whether finished or unfinished compost), kitchen scraps, and the like. This creates a nitrogen layer that you can then place your wood down into.
Work In Your Wood
Ideally, you should have wood that is no higher than halfway up your raised bed, with eight inches of soil below it that is pure and usable for gardening. The height of the raised bed is a factor to consider.
A bed that is 30 inches deep can have up to 15 inches of wood in it and still have 15 inches of soil above that level. However, a bed that is only 15 inches deep should have a maximum of 6 inches of wood. This is because you need to maintain at least 8 inches of growing medium as your top layer for gardening purposes.
The best way to create drainage for shallower beds is to use branches and twigs as your wood source. Bundle them tightly together and tie with a compostable jute. If possible, fill any gaps in the bundle with grass clippings or other organic material. Push the bundle down into your green waste layer.
If you have a taller bed, you can use logs that are taller, but still below the halfway point. It’s best to use dry logs or ones that are already starting to rot, as this will help them decompose.
As you fill your bed with material, make sure to pack down some green waste along the sides. This will help the wood compost over time.
If you don’t have logs, branches, or twigs, you can use wood chips. I recommend arborist wood chips because they come with lots of green leafy material as well as the trunk material. These wood chips compost down faster because they come with a little of their own nitrogen source. Beds using these should add extra organic matter since the wood chips break down more quickly than larger branches.
To create a nitrogen-rich soil, add a layer of wood, then pack organic matter on top.
Fill With Your Growing Medium
After putting the hugelkultur portion of the bed in place, the next step is to add the removed soil back onto the surface evenly. This will enclose the fill material.
The ideal soil for a garden has a lot of organic material and can hold a lot of water. I suggest using a blend like Mel’s Mix or something with a lot of coconut coir and composted manure. You can also add topsoil or other ingredients if desired.
If you’re adding dirt to your compost, make sure you know what kind of dirt it is. Sandy soils may need more moisture, so add extra coconut coir, peat moss, worm castings, or vermiculite. Clay soils should be broken up with leaf mold, plant compost, composted horse manure or cow manure. Silty soils should be well blended with your other components so they don’t settle on the bottom.
You want the soil to be moist, but not waterlogged. To test this, take a pot of the soil mixture and soak it. If any water sits on the surface for more than a few minutes, work in some coarse sand or add some perlite to improve drainage.
Plant It And Mulch It Well
It’s time to plant your garden and mulch it to prevent weeds. Cover the entire soil surface to reduce the chances of weeds taking over.
Raised garden beds made from hugelkultur may help to retain water once the wood starts to compost. However, it is important to reduce moisture evaporation in the upper part of the growing medium, as is the case with all raised garden beds. For the first growing season or two, it is best to use something to slow evaporation from the surface, such as a thick layer of compost followed by a layer of wood chips. This will also help to reduce weeds and water waste. To reduce water waste even further, use a soaker hose system to water underneath the mulch layer.
Hugelkultur raised bed number one
Using a shovel or hoe to dig into our dry clay soil is very difficult because it is almost like trying to dig into rocks. I’m surprised that the blades on the shovel and hoe don’t break when we try to push them into the ground.
I removed the cherry tree stump myself, but it would have been easier to dig in that spot if I had just skipped the stump removal and moved directly to hugelkultur.
We dug a hole, then layered logs and branches on the bottom. Next, we added layers of compost, soil, and mulch. Finally, we added more layers of compost and soil.
After my seedlings grow, I’ll add a layer of mulch. Mulch helps the soil hold onto moisture, so I won’t have to water as often. With the drought in California, I’m really focused on conserving water.
Hugelkultur raised bed number two
I started the second hugelkutur bed by almost directly placing branches on the soil, after removing the weeds and leveling the bed. The smaller branches are at the bottom, followed by smashed Halloween pumpkins, compost, and soil.