Garden beds require a few components: compost-rich soil full of nutrients with good drainage; soil that is warm enough for seeds to germinate; and moisture to keep plant roots hydrated. Gardeners will spend countless resources creating those conditions through watering, compost, fertilizer and tilling, but you can create those conditions without outside work, by building a hügelkultur.
What is a hügelkultur?
A German concept, a hügelkultur is a mound of organic materials that compost internally. The way in which the organic material is stacked is critical to the success of the bed, as it ensures the composting happens in the most efficient way possible. Large materials like logs inhabit the bottom of the mound, layered with smaller and smaller material as you stack, finishing with soil on top. Oklahoma State has some beautiful illustrations that help visualize how the stacking works. The top of these mounds are exceptional for planting in, and the beds become more successful over time. As the middle of the mound breaks down organically, it creates compost-rich soil, full of microorganisms, worms and mycorrhizae (beneficial fungus). The composting creates heat as the material decomposes (if you’ve ever seen a compost pile steaming, that’s the decomposition). The humus-rich soil holds onto moisture, but has terrific drainage, due to all the tiny tunnels that worms and fungi are creating.
Materials for a hügelkultur bed
A hügelkultur bed is like building a fire in reverse—you begin with big pieces, and then fill in the spaces with smaller and smaller matter. The smaller material will compost fastest, “igniting” the larger pieces. You’ll want logs, either long ones or rounds for the bottom of the heap. Then branches, and then scrub, chips and topsoil.
Since this is usually when people prune their trees, it’s the right time to score free logs. If you pay attention, you’ll note neighbors having their trees trimmed, or the city doing some proactive work before winter storms. You can always stop and ask for those logs—and the logs are the hardest part to source; everything else is easy.
One note about collecting logs is that you want to avoid these species of trees: anything allelopathic (these release toxins that suppress the growth of plants around them) like Black Walnut; anything that will grow from cut green branches, like willow; anything invasive, like Tree of Heaven; and finally, anything that resists decay, like cedar.
Designing your hügelkultur
Your bed can be any length, but the longer you make it, the more material—including large logs—you will need. The height of them isn’t prescriptive—they should fit the space—and your beds don’t need to be straight lines, either. Since you’re building from scratch, you can fill a space with a serpentine bed, or design a circular bed around a focal feature. It helps to plan for your bed by laying down garden hoses in the space in the shape of the bed to see how it fits.
You’re unlikely to build your bed in a day: A hügelkultur is a process, so while you can put materials aside to start, you don’t have to lock in a final design ahead of time. You can adjust as you go to fit the space and materials. Once the initial layer is in, you’ll be able to reassess and determine what materials you need as you go so you can collect them.
How to assemble a hügelkultur
You will always start your bed by laying down the logs. These should take the same rough shape that you want the bed to have, and should be placed as close to one another as possible. You’re always endeavoring to have as little empty space between them as possible. Remember that the bed will become wider than the logs, due to the material that is laid on top.
Next, you’ll layer in branches, starting from the thickest to the puniest. Layer them on top of the log, but also tuck them into the spaces left by the logs, cutting them to fit as necessary. The goal, as before, is to fill as much space as possible. This part is where you’re most likely to find you need to collect more material, or specific material, as you fill the spaces and discover you need smaller branches or larger ones. Again, thinking of this as a fire is helpful.
The next layer is scrub, and this can take many shapes. For instance, you can use all the biomass from your summer garden—all the vegetable and flower plants you were going to compost. Grass clippings are good input for this layer, as is manure. The smallest trimmings from your fall cleanup will work, and you can also use wood chips. The idea, at this point, is to fill in all the remaining spaces and create a layer on top of the branches and logs. This type of garden waste is flexible and can be tucked anywhere. So long as it is not diseased, any biomass destined for the compost bin is a good candidate for your hügelkultur bed.
The final layer is topsoil, and as this is the finest material in the mix, it should fill in any remaining spaces left, and create that mound shape. Topsoil doesn’t have nutrients in it; it’s a blank canvas. You can use compost or a three-way mix from the nursery, which would give you a good medium to plant into, but the point of hügelkultur is to create that material on your own—it simply takes some time for the bed to get going. Topsoil is easy to obtain; someone is always giving some away on Craigslist or similar sites, and you likely have it in your own yard.
Once you’ve assembled your entire bed, you’ll need a layer of mulch on top. You can use leaves, straw. or more wood chips. Give the bed a good layer of mulch and then water the entire bed to kick off the compost process.
Planting in your hügelkultur bed
A good reason to build your bed now is so it gets to “cook” over the winter; by spring, it will be ready to receive plants. When it’s time to plant, you’ll move aside the mulch so the roots of your plants have access to the soil underneath and then plant as normal. You won’t need additional inputs like fertilizer, even if you normally use it when planting. When moving the mulch back, leave room around each plant so the mulch isn’t touching the plant.
At this point, treat the bed like you would any other. It might need water occasionally, but should hold onto moisture better than regular raised beds. Over time, the bed will become more productive and efficient, as the interior heats up and the bed composts.
Hügelkultur beds are an important part of creating permaculture in your garden, where all the waste is fed back into the garden, creating a loop.
