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Field trials identify more native plants suitable for urban landscapes

The Issue

California's landscape horticulture industry is constantly growing due to population growth, housing expansion and refurbishing of older urban areas. This industry growth requires an almost constant input of new plant material to address a variety of horticultural needs and tastes.

Historically, many landscapes were planted with species requiring large amounts of water, fertilizers, and pesticides to remain attractive and healthy. One significant result of this practice has been increasing levels of chemicals in urban water run-off to watersheds, leading to negative impacts on the health of the aquatic ecosystems. In addition to this, widespread use of inappropriate plants in a summer-dry climate can contribute to a shortage of water in areas supplied by seasonal snow-melt.

For these reasons, the nursery and landscape industry is in constant need of a supply of new, beautiful, drought-tolerant and disease-resistant plants.

What Has ANR Done?

A program was initiated at the UC Davis Arboretum to identify plants that were suitable to the Central Valley's climate. These plants were designated "Arboretum All-Stars." In cooperation with UC Cooperative Extension specialist Lorence Oki, trials were performed by UC Davis graduate student Karrie Reid to test the landscape potential of ten California native plants on the "All-Stars" list, but not currently in widespread horticultural use. These were screened in open-field conditions for low-water tolerance once established. Their growth, health, and appearance were monitored on four irrigation levels based on reference evapotranspiration as recorded by a local CIMIS (California Irrigation Management Information System) station.

Six of these plants performed well on a low-water regimen, and were subsequently placed in demonstration gardens in seven summer-dry counties, from Redding to San Diego, to further test their tolerance of California's varied climatic conditions. Master Gardeners in these counties are making ongoing observations on these plants.

These observations are being used to determine which plants are suitable for introductions in their region of California. The next ten trial species are in the establishment phase, and will be tested for drought-tolerance in summer 2009. They are currently being distributed for planting into the demonstration gardens as well.

The Payoff

Trials lead to commercial introduction of regionally appropriate plants

The California Center for Urban Horticulture, based at UC Davis, is coordinating the information provided by the UC Davis Arboretum and disseminating the results of the field and demonstration trials to partners in the commercial horticulture industry. These cooperative efforts have led to an introduction schedule of attractive, drought-tolerant plants for California's nursery and landscape industries.

More than 50 retail centers will carry these plants with the label "UC Davis Arboretum All-Stars" starting in spring 2009. The plants will be available throughout California. Additional retail centers will carry the plants
in fall 2009.

More than a dozen UC Davis Arboretum All-Star plants will be offered for the spring
2009 launch, with another dozen or more for fall 2009.

Clientele Testimonial

"We're excited about offering these sustainable plants to California gardeners. With
our heightened awareness of the water crisis, these low-water plants are both beautiful
and smart choices for home landscapes."

-- David Fujino, Director, California Center for Urban Horticulture


Supporting Unit:

Department of Plant Sciences and Landscape Architecture Program, UC Davis
Lorence (Loren) R. Oki, Ph.D.
Landscape Horticulture Specialist
UC Coopeative Extension
Department of Plant Sciences, MS6
University of California, Davis
One Shields Avenue
Davis, CA 95616-8780
(530) 754-4135

Karrie Reid, Junior Specialist
UC Cooperative Extension
Department of Plant Sciences
University of California, Davis
One Shields Avenue
Davis, CA 95616
(530) 754-4883

Ellen Zagory
Director of Horticulture
UC Davis Arboretum
University of California, Davis
One Shields Avenue
Davis, CA 95616