Hügelkulture

Because it’s time to start planning those gardens, folks.

And because there are all these broken trees after that last nor’easter.

Hügelkulture (pronounced HOO-gl-culture) is the most fun word ever to come out of agriculture. Sounds like the hoopla around faddish felt gnomes or something, doesn’t it? Or maybe a really bad New Mexico cannibal movie. 

Definition of Hügelkulture: a horticultural technique where a mound constructed from decaying wood debris and other compostable biomass plant materials is later (or immediately) planted as a raised bed. Adopted by permaculture advocates, it is suggested the technique helps to improve soil fertility, water retention, and soil warming, thus benefiting plants grown on or near such mounds. (Wikipedia)

Fun word just got not fun. So perhaps a definition of the definition is necessary?

Hügelkulture is translated from the German as “hill culture”. This is more than simply making a raised bed. The idea is to pile up decomposing material into a half-moon-shaped mound. The mounds can be any height, depending on how they will be used. Foresters will cover downed trees with small branches, leaves, and soil all in piles up to ten feet tall and let the pile decompose in place, creating ideal nursery conditions for seedling trees. Most garden variety mounds will be under four feet tall because that is also how wide the beds will be — and 4 feet is a comfortable work width.

The idea behind these mounds is that the woody base will decompose slowly and gradually add carbon to the soil — while, yes, sequestering that carbon in the soil. The hills, like all raised beds, improve drainage and are easier to warm in the spring, though unlike raised beds, they do not dry out or freeze as easily because the hills are very deep, the top of the hill is covered with denser soil and mulch to prevent water loss, and the bottom is a heat-generating rotting log. Hills can also be used to direct or contain surface water — a technique usually used in conjunction with some sort of ditch or swale. Some piles are intended merely to serve as slow-acting compost piles, but most gardeners will plant in them. Because why would you want all that space that isn’t growing stuff?

What goes on top of the woody base is determined by what you intend to plant in the hill. If you want to plant perennial herbs and flowers — things that will develop roots as the mound decomposes — then there is less immediate need for a deep topsoil layer than if you want to grow your tomatoes or rutabagas in the hill. Generally, the idea is to put the slowest decomposers on the bottom and work up to soil on top. Things that are woody but small should go on top of the base layer of thick branches and trunks. Usually, a layer of grass turves will go on this wood layer both to make a smooth surface on the wood and to introduce soil organisms to the wood.

The next layer is mostly leaves, dried plant material, paper and cardboard. You should add a bit of soil into this dried layer; the idea is to not have so much air space between the particles that roots can’t find water and nutrients. This layer will be about one quarter of the height of the pile above the wood and grass turves base (this stuff above the woody base is the growing medium portion of the hill). The next layer is half-finished (half-rotted) compost; it will be about one half of the growing medium. The half-finished stuff will be chunky but will have about as much fine soil as larger particulate matter. This is where your root crops will be developing, so keep that in mind while determining the thickness of the layer and the degree of un-rotted compost you want cozying up to your carrots.

The final layer of the hill, about one quarter of the growing medium, is good finished compost. To stretch out the compost, which is sometimes a limiting factor (especially in dry regions where it takes years to rot stuff), you can add garden soil as well. If you are planting perennials or shrubs in your pile, you may not need this top layer. Annuals will require a thicker layer of finished soil, with perhaps some silty sand or vermiculite mixed in at the very top to make a seed-bed. But, annual or perennial, you will want some top-covering of mulch to protect the soil and keep the hill from washing away.

Hügelkulture works best with perennials. It’s perfect for an herb garden, especially in cold and damp regions — herbs generally favor warm and dry. Adding a hill to a given width of garden plot also increases surface area. You can fit more plants into hügelkulture than a flat bed. And you can fit in a more diverse selection of plants in the hill because it has variable conditions — micro-climates — up and down it surface. Plants that thrive in the breezy sun at the top will create shade for plants that prefer protected conditions. Plants that need deep root space will go on top; those that have wide, shallow root systems (most of the grasses and many herbs) can go on the sides to help stabilize the soil.

Hügelkulture can also be used for vegetable gardening. The main advantage of the hill over the raised bed in this case is the increased surface area. However, to take advantage of that extra space, you have to be careful about sculpting the hill to have a gradual slope, then plant the sides with leafy or vining crops so as not to disturb the soil. I plant greens and legumes on the slopes. When I’m done with the plants I just cut the stalks to the soil level and leave the roots in the ground — to become soil while holding it all together.

If you plant your hügelkulture with perennial food plants — artichokes, rhubarb, asparagus, berry plants, culinary herbs, and so on — and mix annual veggies and herbs in between the perennials, you’ll have dinner right outside your door every day for nearly the entire growing season. And you hardly have to do anything except waddle out there in the morning and pick stuff off the plants — which, being on a hill, are also easier to reach than those planted in normal garden beds.

Permaculturists love hügelkulture. It creates soil, sequesters carbon, controls water flow and improves drainage, uses up all the woody bits in the garden, increases garden space — AND you can pile it all up and never have to do anything with it again. It will produce great plants year after year without any digging or amending. If you are careful about keeping seeds out of the initial pile and if you keep the mound mulched, the mounds also tend to be less weedy than regular garden beds. And there are also fewer pest issues because this is healthy soil; pests are eaten by healthy soil critters. It is virtually work-free once constructed. This is the real goal of permaculture, you know: to get food (and yeah, ok, flowers) without doing any work.

It should also be noted, for those of us without trust funds to throw at garden maintenance, that hügelkulture is a very cheap path to good garden soil. If you have woody plants and a compost pile going already it’s almost free. If not, it’s fairly easy to get the materials from city parks’ maintenance folks or landscapers (though with both make sure you’re not getting sprayed toxins in the mix — soil critters can’t grow in poison). 

And finally, hügelkulture is beautiful. Gardeners in Central Europe have been using this technique to make gorgeous textured landscapes for millennia — to hide work areas and highlight special plants, to draw eyes and feet along sinuous paths filled with color and scent, to create seclusion and intimate space. Add a bench and you have a perfect meditation garden. Put in a fountain or plant a central fruit tree and it becomes a medieval sanctuary garden. Or build an outdoor oven and you have an open air kitchen. You can bake bread while relaxing with the herbs. The design options are limitless.

So rather than hauling all those storm-downed limbs to the dump — which does not want or need them — lay out a design in the snow and pile the wood on top. You can add the rest of the layers later. (See? Another wonderful thing! It doesn’t have to be done all NOW.)

And, of course, you’ve now got a new word to impress your less garden-savvy friends.