In the photo below you’ll notice a heap of garden refuse (the hugel) in back of a trench dug below grade planted with kale and bok choi varieties (the waffle).
Hügelkultur is a composting process using raised beds constructed from decaying wood debris and other compostable biomass plant materials. The process helps to improve soil fertility, water retention, and soil warming, and improves the insect and bacterial life of the beds around the hugel. Building several hugels around the garden makes a handy depository for the constant outflow of pruning and weeding debris, making it much easier to “compost in place”. I use the top and sides of the pile to stash plants that need a temporary home; clumps of daylilies that needed separating, unexpected plum seedlings, and the like. The top of the pile dries out in my very arid Downeast summer weather so I don’t plant vine crops or flowers there, although many people recommend the practice. Someday, when I have more water available perhaps that will be an option!
The hugel is paired with a waffle bed. Waffles are the opposite of raised beds and are built by removing soil in a small area, replacing and augmenting the best soil available, and then planting below grade. This practice has been used since ancient times in arid climates to preserve water and soil, and to shade roots and seedlings as they develop. The combination of the hugel acting as a windbreak, moisture reservoir, and beneficial critter refuge with the waffle offering fertile soil, bottom shade, and slower evaporation, is hard to beat.
The hugel/waffle combination can be quite small and still provide a significant benefit. Here a small hugel on a slope is planted with Marguerite Daisy (Argyranthemum frutescens). Note that this plant is generally considered a weed for it’s prolific seed production but is also a good drought proof pollination plant. The trenched waffle bed upslope is planted with onion sets, and the small, deep waffles below are planted with tomatoes. Both sides benefit from the hugel providing water diversion and storage and wind protection.
Here a small hugel planted with chives borders a waffle planted with greens: kale, Australian yellow lettuce, spinach, and lettuce var. Pablo.