https://en.wikipedia.org/wiki/H%C3%BCgelkultur
Hügelkultur (German pronunciation: [ˈhyːɡl̩kʊlˌtuːɐ̯], alternative spelling without umlaut: Huegelkultur), literally mound bed or mound culture, is a horticultural technique where a mound constructed from decaying wood debris and other compostable biomass plant materials is later (or immediately) planted as a raised bed. Considered a permaculture practice, advocates claim that the technique helps to improve soil fertility, water retention, and soil warming, thus benefitting plants grown on or near such mounds.[1][2]