For permanent raised beds, native mineral soils amended with small amounts of clean sourced, well-rotted composts can often provide an ideal growing medium for plants. Soil organic matter content of 3–5% is usually considered “high” for native mineral soils, and more than 10% is not recommended for garden use. You can, however, add 1-2″ of mulch on top of your bed to discourage weeds and keep the soil moist. (read more)