In front of the Granite Reef Senior Center in Scottsdale, there’s a parking lot on one side, and off to the other side, there’s a space for the Scottsdale Trolley to stop. Between those areas is a patch of gravel and drought-tolerant desert plants. Six months ago, the senior center’s little xeriscape garden was about 3,000 square feet of turf. But it wasn’t intended as a sports field or a picnic area, it was really just a decorative space to divide two sides of the parking lot.