Hugelkulture 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 brashwood.
The name comes from German - hügelkultur translates as "hill culture".
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 hugelkultur 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
Note that some woods contain natural toxins. Do these break down adequately? By placing them at the bottom of the pit and giving them years to decay, is this problem solved? E.g. cedar, camphor wood, black locust, black cherry, black walnut.
Pine and fir will have some levels of tanins, but sawdust from these woods these 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.
- hugelkultur - richsoil.com article with explanation and instructions, including pictures and video.