Earlier in June, at the Garden Stage at Sunset's Celebration Weekend, speakers and audience alike all were talking about gardening during the drought. Sunset's friend, horticulturist Janet Sluis (she curates our awesome line of low-care plants, the Sunset Western Garden Collection), mentioned the intel available thanks to the UC Davis Irrigation Field Trials for Landscape Plants.
What the magnificent garden geeks at Davis do is grow an array of landscape plants in real situations throughout California (in 12 of the Sunset Climate Zones), and test how little water they need to survive: "After being grown for a full year on a regular watering regime to establish deep, healthy roots, plants are irrigated through the second year at four levels, ranging from 20-80% percent of normal evapotranspiration…" Then they study the health and performance of each plant.
Go the their site to view reports from several years, plus access a trove of smart gardening advice. Perhaps best of all, check out their All-Stars list and database—100 tough plants that have been tested in the UC Davis Arboretum. A fantastic resource! And check out these 10 favorite and surprising low-water plants from Sunset's own test garden.