As more California gardeners add drought-tolerant plants to their landscapes, growers and hybridizers have responded to the increased market demand by producing new cultivars of many perennial plant types. Some of these experimental efforts will make it to nurseries and garden centers; some will not.
For the last three two-year growing sessions, I have been among groups of professional landscapers and horticulturalist and other Master Gardeners participating as raters for new drought-tolerant cultivars for the UC Landscape Plant Irrigation Trials in Davis. The rating sessions and open houses are held three times a year, in late April or early May, July and September in the middle of a shadeless field south of the UC Davis campus.
The plants selected for rating were formerly chosen from the UC Davis Arboretum All-Stars lists, but now are new varieties from growers and hybridizers.
The plants are well-irrigated for the first year so that they develop good root systems and then are divided into three groups according to the level of water received (low, moderate and high).
The rating system used by our group is fairly simple; the ratings system used by UC staff is much more complex and ratings are performed much more frequently. We are asked to evaluate on a numerical scale how profusely the plant is able to set flowers. We’re asked to examine foliage for browning and leaf tip burn, signs of heat or drought stress and pest or disease problems and, finally, to judge the plants’ overall appearance. Basically, we’re looking for plants that can look good, flower well and continue to grow and stay healthy in the hottest, driest months. Plants in the study include flowering bushes, groundcovers, grasses and small trees. Our groups’ ratings are observational only; the UC staff’s ratings are, of course, research-based.
You can check ratings and see photos for the previous years on the California Center for Urban Horticulture website, ccuh.ucdavis.edu/uc-field-trials. Plants with higher ratings might be available soon at your local nursery.
I was impressed with several types of plants that were tested in the last (2016-2018) session. The Knockout series of groundcover roses, especially Pink Knockout, were all excellent performers – full of roses and very healthy. The flowers on African Gold, a new cultivar of Dietes bicolor (aka African iris or Fortnight Lily), were gorgeous, bright gold. A new (to me) taller grass, Lomandra fluviatis, swayed in the light breeze like a graceful ballet dancer. Two smaller bush-sized crepe myrtles also stood out for flower production, leaf color and berry production.
As you visit the drought-tolerant sections in nurseries and garden centers in the coming months, be on the lookout for new varieties. Our choices are getting bigger every year.
Master Gardeners free class
The Fresno County Master Gardeners are offering a free class on planting and growing cool-season vegetables Saturday, July 27, from 9:30 to 11 a.m. at the Fig Garden Regional Library, 3017 W. Bullard Ave in Fresno.
Our short, mild winters allow us to grow a wide variety of cool-season vegetables from September until April. Fresh beans and a big green salad with Thanksgiving dinner and spinach omelettes for Easter brunch are all possible for Central Valley gardeners.
Register online at ucanr.edu/sites/mgfresno under Adult Education Classes.