The staple foods then used by other indigenous American tribes, corn and/or potatoes, would not grow without irrigation in the typically short three- to five-month wet season and nine- to seven-month dry seasons of California (see Mediterranean climate). Despite this, the natural abundance of California, and the environmental management techniques developed by California tribes over millennia, allowed for the highest population density in the Americas north of Mexico. The indigenous people practiced various forms of forest gardening in the forests, grasslands, mixed woodlands, and wetlands, ensuring that desired food and medicine plants continued to be available. The Native Americans controlled fire on a regional scale to create a low-intensity fire ecology which prevented larger, catastrophic fires and sustained a low-density "wild" agriculture in loose rotation. By burning underbrush and grass, the Native Americans revitalized patches of land whose regrowth provided fresh shoots to attract food animals. A form of fire-stick farming was used to clear areas of old growth, which in turn encouraged new growth, in a repeated cycle; a primitive permaculture.