Hugelkultur: The Ultimate Raised Garden Bed?

Building a raised garden bed by Hugelkultur guidelines mimics the way a forest uses organic matter, but in reverse. It’s an ancient way of building a garden bed and a popular permaculture method.

I hate wasting perfectly good tree wood. I recycle my Christmas trees as mulch, garden borders, and wildlife habitats. Whenever I remove a tree from my property, or do extensive pruning, I find a use for as much of the wood as possible, if it’s not diseased. Whatever I can’t use I haul to the municipal composting pile. When I built a garden bed with the Hugelkultur method I put that tree wood to good use only feet from where I cut it.

What is Hugelkultur?

Hugelkultur (HOO-gul-kul-ture) is a German word that translates as “hill culture” or “mound culture”, depending on who you ask. Practiced for centuries in Europe, it’s a way of making a raised garden bed with woody debris and allowing it to rot in place. The decomposition of the wood releases heat, which has many benefits for a garden bed, not the least of which is the ability to extend your planting season. The decomposed wood also becomes sponge-like, holding water and storing it for when your plants need it. And with the addition of that fertile compost under your plants, there will be no need for adding fertilizer to your garden.

Hugelkultur garden beds act like a forest floor in reverse

Considered a cornerstone of permaculture systems, raised Hugelkultur garden beds mimic the nutrient cycling of the forest floor, but in reverse (or upside down might be more appropriate). Anyone who’s picked up semi-decomposed wood in the forest knows how wet and soft it is on the bottom where it laid against the forest floor. You may also have seen fungi growing on that wood. Now imagine a lot of that slowly decomposing wood below your garden plants, releasing energy and nutrients, feeding their roots. The rotting wood creates a rich, deep, loamy, fertile soil, and an ecosystem where bacteria and fungi thrive, essential for healthy plants.

Where is it best to build a Hugelkultur bed?

Difficult soil areas like urban lots, or those with poor drainage or heavy clay, can benefit most from this method, as you’re essentially growing your plants in a sheet compost pile mixed with soil. Hugelkultur garden beds are especially useful in arid climates, even in deserts, as the Hugelkultur bed’s ability to hold water is vastly superior to a typical garden soil bed. It’s not uncommon for a properly built raised Hugelkultur garden bed to store water for up to 3 weeks. Some gardeners who build very large beds (6-7 feet in height), claim that they don’t require water the entire season.

Can I use any type of wood for the Hugelkultur bed?

Not all tree wood is appropriate for a Hugelkultur bed. Cedar has anti-microbial properties which discourage the development of bacteria and slows its deterioration; Black Walnut contains toxins which may affect the growth of your plants, or outright kill them; and Black Locust wood is very resistant to decomposition due to its density. Just about any other species of tree wood or woody perennials will work just fine.

How to build a Hugelkultur garden bed

Building a raised hugelkultur garden bed is pretty simple. There’s a lot of labor up front, but little maintenance once established. The bed can be as large or as small as you like – base it on the amount of wood you’ll be using, which can be fresh or already decomposing. Bear in mind that over a period of a few years, the size of the garden bed will reduce by as much as 1/3rd, as the wood decomposes.

1. Build your Hugelkultur bed on the soil surface, or if you’d like it to ultimately be at ground level, start it in a trench.
2. Use the largest logs on the bottom and pack them tightly, allowing as little space as possible between logs.
3. Place branches on top of the logs, followed by smaller twigs and wood pieces.
4. Add liberal amounts of high nitrogen materials like kitchen scraps, sod, grass clippings, manure, etc., known as “greens” in composting. The nitrogen in the greens is necessary for the decomposition process, and they’ll supply nitrogen to your plant’s roots.
5. Water the pile deeply.
6. Add two inches of soil on top of the pile and then add a layer of mulch.

You can plant in the garden bed immediately, but you’ll get the best results if you allow it to “cure” for a season. My suggestion is to build the bed in late summer, plant a cover crop on it. In early spring the following season, cut the cover crop, mulch the bed with it, and then plant.

The best crops to grow in raised Hugelkultur garden beds are potatoes, anything in the squash family, melons, berries, and deep rooted plants like tomatoes and cucumbers. They’re great for native shrubs and flower beds, too.

More information can be found at Permaculture News.