It's not always easy to decide which direction to go when it comes to gardening during the drought. We find endless recommendations for water-wise plants to put in our landscape, from succulents to herbs, but how do we determine how well it will grow in our specific California microclimate?
Turns out, the folks at UC Davis have it all figured out for you. All year long, horticulturists at the College of Agricultural and Environmental Sciences evaluate landscape plants with the potential to be good performers in low-water California gardens. The plants are tested under four different irrigation frequencies for growth, heat tolerance, pest and disease resistance, and attractive appearance.
In these UC Davis Irrigation Field Trials, an array of plants are "grown for a full year on a regular watering regime to establish deep, healthy roots," then "irrigated through the second year at four levels, ranging from 20-80% percent of normal evapotranspiration (total water lost through evaporation from plants and surrounding soil). A weather station collects data to calculate these percentages, while height and width are measured to calculate a growth index for each species at each water level. Overall appearance, flowering time and duration, and pest or disease problems are noted to provide a comprehensive assessment of performance."
In addition, Master Gardeners across the state grow these same plants in demonstration gardens to document their appearance and performance in varied climate zones.
The result is eight years of data collected from dozens of plants, including how much (or how little) water they need to thrive and survive. You can geek out on these results on their site.
UC Davis also compiled a list of Arboretum All-Stars, which identifies 100 tough, reliable plants that have been tested in the Arboretum for ease of growing, low water needs, and resistance to pests, including many California native plants that support native birds and insects.