By replacing the basin’s turf grass with native plantings, the required maintenance of the basin has decreased. Turf grass is unsustainable because it requires regular mowing, watering, fertilizing, and weed control. Native plantings are a more sustainable alternative because they are drought resistant, promote infiltration and biodiversity, and require little maintenance. With dense root systems making up two thirds of their biomass, native plantings enrich the soil with their organic matter. They also have high water-holding capacities and draw water deep into the earth, replenishing the shallow aquifer, because of the great depths their roots reach. Native plants support biodiversity by providing food and habitats for native birds and insects. The growing point of prairie plants is just below the surface, making them resistant to fire; an annual controlled burn is used to maintain the plants and fertilizes the plants with its ash.