Park operations director Jim Hardie calls it the “grasscrete circle”—also known as the TreePeople cistern, a 216,000-gallon underground storage tank, where we save rainwater filtered and collected from rooftops and the Parking Grove. The stored water irrigates TreePeople’s grounds in the warm months. For the past four years, the circle has been planted with wildflowers, which look gorgeous but require regular weeding. Jim is excited about a low-maintenance alternative called purple needlegrass or Stipa pulchra or Nassala pulchra—the official state grass of California!

Purple needlegrass is considered a symbol of the state because it is the most widespread native California grass and it once supported Native Americans as well as Mexican ranchers who followed the Spanish here. “This is a beautiful and tough native grass, with super deep roots, potentially going 20 feet down,” says Jim. “It will hold up to foot traffic (both human and canine), and it can be mowed low when we want to cover that area for an event.” These deep-rooted natives will keep the soil healthy and porous to absorb as much rainwater as possible.

The old soil in the grasscrete circle cells naturally contained seeds from past seasons. TreePeople’s planting team, which included staff as well as volunteers, dispersed it to create new wildflower areas in other parts of the park beyond the watershed garden.