Hugelkultur base layer for deep beds

Hugelkultur (German for 'hill culture') fills the bottom half of deep raised beds (18+ inches) with logs, branches, and woody debris, topped with 12+ inches of quality soil mix. As the wood decomposes over several years, it acts as a carbon sponge that retains moisture, slowly releases nutrients, and generates mild heat from microbial activity. This method can cut soil costs by 40-60% for tall beds. Start with a layer of cardboard on the ground (weed suppression), add 6-12 inches of logs and branches (hardwood preferred; avoid black walnut which is allelopathic), fill gaps with leaves and straw, add a thin layer of grass clippings or manure (nitrogen source to balance carbon), then top with 12-18 inches of finished soil mix. Water each layer as you build. Expect 3-6 inches of settling in the first year as materials compress and decompose; top up with compost annually. Do not use hugelkultur in beds shorter than 15 inches, as roots will reach the undecomposed wood layer too quickly. Avoid treated or painted wood.