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UC Davis Irrigation Field Trials for Landscape Plants

UC Davis horticulturists are evaluating landscape plants with the potential to be good performers in low-water use gardens. Some of these plants have been from the UC Davis Arboretum All-Stars lists, and others are provided by growers and breeders who want to evaluate their new plant varieties for low-water use in hot California gardens. These plants are being tested under four different irrigation frequencies for growth, heat tolerance, pest and disease resistance and attractive appearance.  Additionally, Master Gardener volunteers are growing these plants in demonstration gardens throughout the state, documenting their appearance and performance in their varied climate zones.  The results of these trials are providing growers and retailers the information they need to successfully distribute and market these plants to the public.

measuring in fieldIrrigation Trials

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 (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. 

Results:

 Climate Zone Trials

The same species are distributed to demonstration gardens throughout the state, representing 12 Sunset climate zones.  The project coordinator provides evaluation training to Master Gardeners, who report on general appearance, pest or disease problems, flowering, and other ornamental features (such as durability, size, form, and leaf qualities).  The monthly evaluation data are then compiled or analysis and publication.

These evaluations provide information on the attractiveness and usefulness of these plants in different climates from the perspective of the gardener. This information is made available to gardeners, landscapers and nursery operators through Cooperative Extension and as part of the educational outreach programs of the Arboretum and the CCUH.

Funding has been provided by our cooperating growers and by:

  • The California Association of Nurserymen Endowment for Research and Scholarship
  • The Elvenia J. Slosson Endowment for Ornamental Horticulture
  • The Saratoga Horticultural Research Endowment