In the late 20th Century, permaculture started to become used as a design tool by gardeners and farmers as a way to ecologically design gardens. Permaculture had 3 main guiding design ideas:
- Care for all the people.
- Care for the planet.
- Pass on any surplus created in a system. For example, if a wall retains heat, pass on the heat to a plant that needs it; if a plant provides shelter, place it on a wall that needs cooling.