Hügelkultur (also spelled huegelkultur, roughly translated from German as "hill culture") is the practice of composting large woody material to create a raised garden bed. It is a way of dealing with excess amounts of woody garden wastes, for example prunings, hedge clippings, brassica stems, or brushwood.
The technique involves digging a circular trench about 1' (30 cm) deep and 5' (1.5 m) wide, in the centre of which is dug another hole 1' (30 cm) deep hole. The material is piled in. Turf (grass) is then stacked face down on top, then layers of compost, well rotted leaves and manure, etc as available. The layers break down slowly and creating rich humus over four or five years. It is claimed that this is ideal for growing hungry crops such as zucchinis (courgettes) or strawberries.
As the years pass, the deep soil of the raised bed becomes incredibly rich and loaded with soil life. As the wood shrinks, it makes more tiny air pockets - so your hügelkultur becomes self tilling. The first few years, the composting process will slightly warm the soil giving a slightly longer growing season, in temperate and cold climates.
 Woods containing natural toxins
Pine and fir will have some levels of tannins, however sawdust from these woods are successfully used in composts, typically being allowed to age before mixing with other ingredients.
Wood is high in carbon and will consume nitrogen during composting. This is much less of an issue (if at all) with well rotted wood.
Note that some woods contain natural toxins and are allelopathic. These do break down eventually, though it may take years or decades. Allelopathic trees include:
- most or all cedars (cypress, redwood, sequoia)
- camphor wood
- black locust
- black cherry
- tree of heaven (Ailanthus altissima)
- black walnut (Juglans nigra)
- California pepper tree (Peruvian and Brasilian)
- Siberian Elm
 Other materials to avoid
Avoid using living parts of trees or plants that will sprout and colonize your new hügelkultur bed, such as willows, acacia, nutsedge, bamboo, or rubus species. If you must use them, make sure they are thoroughly dead first.
 Where used
- hugelkultur - richsoil.com article with explanation and instructions, including pictures and video.