When thinking about gardening, we tend to focus on plants, soil, water, and perhaps mulch or organic fertilizer. Few probably think about mushrooms, yet it’s estimated that approximately 80% of plants partner with mycorrhizal fungi to exchange nutrients, water, and carbon. That means most of us are also gardening with fungi, we likely just don’t realize it!
The symbiotic partnership between fungi and plants offers many benefits that vary by species and can include, but are not limited to:
Improved plant health, including more nutrient-dense food crops
Increased pest resistance
Enhanced ability to tolerate environmental stresses (i.e., drought, high soil temperatures, soil salinity)
Greater soil stabilization and ecosystem resilience
Enhanced carbon sequestration and the resulting accumulation of healthy soil
Of the non-mycorrhizal plants, a few include most brassicas, spinach, chard, beets, rhubarb, and a number of hard early succession plants (commonly thought of as weeds) like lamb’s quarter, pigweed, mullein, and purslane. Interestingly, another symbiotic benefit of mycorrhizal fungi in the garden is their ability to suppress nonmycorrhizal weeds.
I unknowingly began gardening with mushrooms in 2013 when I built my first hugelkultur raised bed garden. This German term loosely translates to ‘hill culture’, where rotting tree trunks, branches, and woody debris are buried beneath compost and/or soil in a mound. At the time, I had no idea I was inoculating my garden with local mycorrhizal fungi, I simply was looking for a way to repurpose the ‘yard waste’ that had been accumulating in our small urban lot in Duluth, Minnesota.
In the decade that’s followed, I’ve built dozens of hugels to grow garden crops, serve as nursery beds for comfrey and other perennials, stabilize bare slopes, and create animal habitat. I also credit hugels for my success as a gardener. All of my pre-hugelkultur gardening attempts had ended with lackluster results and initially led me to believe I wasn’t much of a gardener.
Below I outline the various benefits and considerations of hugelkultur gardening as well as a basic overview of how to build a hugel (with photos).
Benefits of Hugelkultur Gardening
As a regenerative farmer, I spend a lot of time and energy building and maintaining healthy soils. Plants are no different than humans in that we derive our nutrition from the foods we eat. Since gardeners usually want to grow nutritious and healthy food, it makes sense to focus on practices that build topsoil composed of a diverse and healthy soil ecosystem – including mushrooms.
As I’ve learned in the years since I stumbled onto hugelkultur gardening, mycorrhizal fungi play a crucial role in soil health. According to Michael Phillips in his book Mycorrhizal Planet, these fungi are “the normal nutrient-absorbing organs of the majority of plant species,” with normal meaning best or ideal. The benefits for plants of symbiotically partnering with mycorrhizal fungi can start as early as the seedling stage (assuming the fungi are initially present in the soil). These benefits include preventing “damping off” disease, supporting root initiation on plant cuttings, and reducing transplant shocks.
I like building hugels because they mimic how nature builds healthy soil ecosystems and thus healthy soil – from the top down using naturally occurring woody debris. By working with nature and inviting a diversity of soil microorganisms (via the woody debris used in the core of the mounds), we create something that is greater than the sum of its individual parts.
In the next section I’ll discuss a few considerations or challenges for hugelkultur gardening, but first let’s quickly look at some of my favorite benefits:
No digging required since your building up
No need to remove sod (unless you want to)
No carpentry skills required
Ideal way to repurpose ‘yard waste’
Works in any soil type (particularly beneficial for clay or sandy soils)
Void spaces throughout the mound provide ample room for plant roots to grow
Elevated growing surface dries faster, is less prone to flooding, and can be worked sooner in the spring
Creates multiple microclimates within one raised bed (more pronounced in larger hugels)
Larger surface growing area (compared to a flat raised bed)
Increase water and nutrient retention as the woody debris breaks down
Increased heat from decomposition of stacked organic matter (particularly noticeable the first year or two)
Inoculates garden with local mycorrhizal fungi
Hugels are a versatile style of garden bed that can be used for more than just annual vegetable crops. There’s a lot of potential outside of the garden, especially if you simply want to “upcycle” your woody debris and build healthy topsoil for future projects. It’s been fun to experiment with hugels and I encourage everyone to at least build one hugel in their lifetime!
Interesting Considerations for Hugelkultur Gardening
As you’ve probably recognized by now, I enjoy gardening with hugels. So much that I have almost exclusively built and grown crops in these mounded raised beds since I started my first one in 2013. Part of my loyalty to hugelkultur gardening is the ease in which it allows me to raise healthy plants, even in brand new hugels.
Despite all of the previously mentioned benefits, there are tradeoffs to consider. This will be especially true for folks used to using machine-powered implements in the garden or growing crops on flat ground.
Physical labor required
Building small hugels doesn’t require much material or labor, but larger hugels require both. I’ve always relied on human-power, but larger projects may benefit from using equipment to move and place larger woody material. The process can go quicker with multiple people; however, I’ve built all of our hugels by myself.
As previously mentioned, I prefer to build new hugels in the fall since I can approach the project more casually knowing I won’t be planting it until the following spring. It also allows me to stockpile materials nearby in advance to cut down on future labor and time. This is particularly useful if you can stockpile topsoil, compost, leaf mold compost, etc.
Gardening on sloped and sometimes lumpy surfaces
For those who are accustomed to growing crops in flat garden beds, growing on hugels will offer a new experience. For small hugels with minimal side slopes, it won’t be as pronounced, but large hugels that are four to six feet high, gardening on the steeped slopes has a learning curve.
The sloped sides of the mound also don’t allow for the use of rototillers, walk-behind tractors, and the like. In the eyes of the mycorrhical fungi that we invite into our gardens as part of the hugelkultur building process, this is a benefit since they thrive in non-disturbance conditions. Hand tools and broadforks work just fine on the sloped surfaces of hugels.
I always try to mulch my crops for a number of reasons, but I’ve found it to be especially important when gardening with hugels to reduce soil erosion from watering on a slope. When I fall behind on mulching, I always regret it because I have to be extra careful when watering, especially if the soil has already started to dry out. I use drip hose to do most of our watering and supplement with a wand hose attachment that allows me to gently water our hugels. Mulching in the fall or using cover crops will also reduce wind and water erosion during the off-season and will be appreciated by the mycorrhizal fungi.
The surface of a new hugel can also be lumpy as the woody debris breaks down and settles. Throughout the growing season, I simply add more compost or aged animal bedding to keep things leveled out. It is more of an aesthetic issue than a crop growing issue and easily remedied when prepping your beds for planting.
Lastly, setting up caterpillar tunnels or other protected environments for growing early or late season crops can be more difficult on a mound. I’ve used tomato cages, buckets, and other supports to prop up row covers. Since I’ve always grown crops on hugels, I didn’t have to modify equipment, tools, or supplies designed for flat bed gardening.
Growing root crops
As you might guess, growing root crops into a bunch of sticks, branches, and woody material is less than ideal, particularly if they are located just below the ground surface. If I don’t have other areas to grow these crops in (including more mature hugels that have mellowed out), I try to grow root vegetables in the areas in the hugel where there is greater soil depth or I add more compost to give that area greater depth.
Potatoes are one of the crops I prefer not to grow in hugels, yet each year I still do grow them in our hugels. They grow fine and are happy enough. The problem is in harvesting the tubers – or thinking you have harvested most of the tubers only to discover volunteer potatoes growing the following year. I’m in the process of sheet mulching my first non-hugel garden area to grow potatoes and other crops that require larger areas to grow, such as winter squash, corn, and grains.
Despite these challenges, I’ve always grown root crops in our hugels and made peace with odd shaped carrots and parsnips that can sometimes be hard to extract from the woody material if they have grown deeper into the hugel. As our hugels mature, this becomes less of an issue. Rutabagas, turnips, beets, kohlrabi, onions, garlic, and radishes do fine in these woody mounds.
Building a hugel, especially if you start in the fall and finish in the spring, invites woodland friends. We have always shared our hugels with chipmunks, the occasional garter snake, and toads (as well as all our soil microbe friends).
It can be frustrating to see pea seeds dug up, tomatoes munched on, or a new chipmunk tunnel entrance knocking over a bean plant, but I try to garden with an abundance mindset and accept that building my garden disturbed the wildlife that called that particular spot home before I took it over. I also remind myself of the benefits chipmunks provide, including spreading fungi around the gardens, eating slugs, and hunting mice. Over the years, we’ve suffered minimal damage from chipmunks, so I try to enjoy their presence as part of our garden ecosystem.
I’ve also intentionally built hugel-type mounds to stabilize slopes as well as to intentionally create snake habitat near our apiary. Mice can be problems for bee hives in the winter months, so I do what I can to make the area surrounding our hives attractive for snakes.
We have had two instances of ground wasps building nests in our hugels. I safely identified their entrances and treated their hives similar to how I behave around our our honey bee hives. Mostly, I avoided approaching from the front and didn't work in the immediate area when the wasps were active. With these precautions, I had no issues and was able to grow and harvest crops in the vicinity of both nests. I did momentarily forget about one of the nests when I went to harvest potatoes. I quickly remembered as I was pulling out a clump, promptly stopped, and left the area before the guard bees sent out any alarm pheromones.
For being complex and biologically amazing structures, hugelkultur raised beds are pretty straightforward to construct and can cost nothing since its ideal to use locally available materials. If you have a yard or live anywhere with trees, you have everything you need to build a hugel! No carpentry skills required.
When I built my first hugelkultur, I was still working as an environmental engineer, which involved a lot of computer work indoors. I decided to start gardening to 1) increase the amount of outdoor natural movement in my life, 2) serve as a creative outlet, and 3) reduce the footprint of our monoculture lawn while creating an edible urban oasis for humans and wildlife. I had no idea this evening and weekend hobby would eventually turn into a farming career!
As mentioned above, building hugels is a form of recycling woody debris such as tree trunks, branches, sticks, leaves, and other typical ‘yard waste’. The building process is pretty straightforward, once you have the necessary building materials gathered. If you have already been stockpiling woody debris in piles adjacent to your future hugel, then you have a large part of the work already done.
Below is a series of photos of the first hugel garden I built when we lived in the city of Duluth, Minnesota. Our soils were heavy clay, so building up was necessary. The large hugel that is primarily featured was my first hugel bed and measured approximately 20 feet long, eight feet wide, and was initially around three feet tall. The other five that were built were all much smaller and sized to fit in the remaining space while retaining a small but functional area of lawn (in the hopes that a future homeowner wouldn't tear out the gardens and replace them with lawn).
Hugels can be built to any size and match whatever terrain you have. I like to add at least one or more layers of thick cardboard (or lots of overlapping smaller sections) to smoother the sod beneath. I like to extend this cardboard layer out several feet in all directions beyond the border of each hugel. I will often woodchip this area and use it as a permanent path, refreshing the cardboard and/or woodchips each spring to keep the surrounding ground cover at bay.
As shown in the photos above, when building hugels, start with the biggest wood first, especially when working with stumps, larger logs or branches. Throughout the building process, I like to sprinkle in leaves, grass clippings, half finished compost, old potting soil, or animal bedding, especially if I am making a large hugel.
In the north, building hugels in the fall takes advantage of winter snow cover to compress an unruly mound and reduce the amount of large void spaces. You can also do this by approaching the building process like a jigsaw puzzle and intentionally place the different layers to minimize creating large void spaces. Throughout the building process, I also walk on, or even jump on (if it’s safe to do so), the hugel to help compress each layer.
Early on, the wood core of the hugel will account for more than half of the volume and may result in steeper sides. You can reduce this steepness by adding more covering material like compost, animal bedding, grass clippings, moldy hay, etc. Over time, the woody center will decompose and gradually begin to look similar to a conventional raised bed.
When I built my first hugels in our urban yard, I lined the edges with rocks to both shore up the cover material and to make the garden beds more aesthetically pleasing. The aesthetic piece was important in an urban setting, especially when the building process aroused a great curiosity by our neighbors. On the farm when I built our current market garden hugels, I didn’t bother adding a border and sometimes grow crops along the edge between the hugel and walkways.
Give it a Try!
If you are interested in gardening with mushrooms, I encourage you to try building your own hugelkultur raised bed. During our farm tours, there’s always a lot of interest in and questions about our hugels. Their mounded appearance intrigues people since most are only familiar with conventional flat garden beds. It probably doesn’t hurt that our hugel garden beds are often thriving with healthy looking produce that even non-gardeners can appreciate.
Gardens can be such beautiful spaces and hugel raised beds are a wonderful canvas to create attractive edible and medicinal works of arts. Hugels are also an ideal way to turn marginal land into vibrant garden spaces. There are so many interesting ways to build and locate hugels that you are only limited by your own imagination.