Hugelkultur Bed: Creating the Perfect Soil for Your Garden

The foundation of a hugelkultur bed, or mound, is decaying wood. It starts with a pile of branches and logs, and even raw lumber — meaning not pressure-treated wood, which can leach chemicals into your soil.

It should be piled as high as 5 or 6 feet (1.5 or 1.8 meters), and topped with grass clippings and plant debris. Really, any green, nitrogen-rich compost material will do! Follow that with a thick layer of topsoil and top it off with mulch.

Essentially, what you're building is a compost pile that'll decompose in place. As it does, it becomes a nutrient-dense, spongy bed that feeds plants and remains drought-resistant. It can even extend the growing season in your garden, thanks to the heat generated by the decomposition process.

Because the base of the mound is a pile of fallen branches and plant roots, it also means you can build a garden bed large enough to accommodate a lot of plants while using very little soil. That makes hugel beds an economical choice for many growers.

Once a hugelkultur garden bed is established, it'll last for a number of years, and the growing medium will actually improve from season to season. It's a self-sustaining method that requires little upkeep and can drastically increase a garden's yield.

Step 1. Choose Your Location

First, decide where to build your hugelkultur mound. Look for an area that gets sun for most of the day. If there's a slope nearby, situate your hill mound perpendicular to it, so as to catch as much rain runoff as possible.

A site at least 8 feet (2.4 meters) long by 4 feet (1.2 meters) wide is ideal; you want to give the hügel a wide base to prevent collapse.

Step 2. Create a Clean Base

Once you've chosen the spot, clear it of grass and weeds. Just piling the brush on top likely won't be enough to prevent weed re-growth, so make sure you smother any existing foliage with cardboard or newspaper.

Step 3. Dig Your Pit and Begin to Fill It

Once the soil is clear, dig down about a foot (0.3 meters), setting aside the topsoil to use later. In the pit, start to pile logs, branches, twigs and other wood, keeping the pile as tight as possible. It's recommended you use a mix of softwoods — think pine, fir, cypress and other conifers — and hardwoods like maple and red oak.

Try to limit the use of woods like cedar and redwood, which take a long time to break down. Avoid pressure-treated or painted lumber, which can leach toxins into the garden and its plants; be cautious about using black walnut wood for the same reason.

Step 4. Create Alternating Layers of Material

Once the mound grows to a few feet, start to layer in soil and compost such as grass clippings and straw. Keep alternating with layers of wood until the mound is close to the desired height; that might be anywhere from 2 to 6 feet (0.6 to 1.8 meters) tall, but keep in mind that it will shrink considerably as the wood composts.

Top it off with a final layer of soil and then cover the whole thing in mulch. Finally, water it well, and keep it very moist for at least the first few weeks.

The ideal time to start a raised garden is in the fall. Over the winter, the decomposition process begins and creates good planting conditions when the weather warms. But that doesn't mean you can't get started on your hugelkultur raised garden bed in the spring.

In fact, it's never too early to start a hugel bed, planting on top of it as it decomposes underground. The wood will eat up nitrogen as it begins to rot, but you can help maintain the health of your mound by planting nitrogen-fixing plants like beans and peas during the first year.

Once your hugel is a season old, the wood inside will have begun to break down, and the mound will be like a big sponge, ready for diverse plants. The base of the mound will be consistently more moist than the top, so it's wise to plant more drought-tolerant varieties at the peak of the mound, and those that need more water further down its slope.

There are few drawbacks to growing in a raised garden bed. Wood and termites go hand in hand, but termites look for dead wood to infest and don't like to compete in moist green zones.

A hugelkultur bed is made of rotting vegetation and contains lots of worms and bugs and bacteria. So, although it may attract some termites, they won't thrive. Actually, they might be beneficial by working to decompose the organic matter. But if you live in an area where termites are a major concern, you will want to keep the beds at least 30 feet (9 meters) from your home.

As long as you have an outdoor space and access to some woody material, raised beds should work for you. And once it's established, a hugelkultur garden will remain productive and easy to take care of for many years to come.