Climate-Ready Landscape Plants Project
Originally starting as the University of California Landscape Irrigation Trials (UCLPIT), this project expanded to field sites across the Western U.S. The goal of this project was to create a non-biased plant trials network that evaluated landscape plant performance under different irrigation regimes and promote the production and utilization of low water-use plants to the horticultural industry and the public. Researchers on the project conducted outreach in the form of field days, presentations at workshops and conferences, publications in scientific journals and trade magazines, and social media to share the information with industry stakeholders and the general public. This project is conducted at 6 different field sites: the University of Washington, the University of California-Davis, South Coast Research and Extension Center, the University of Arizona, Utah State University, and Oregon State University North Willamette Research and Extension Center.
Experimental Setup
Between each site, 40+ different taxa were tested with 6 taxa common to each site. Within a site, 15 different taxa were tested with 24 replicates per taxa (8 plants per irrigation treatment) for a total of 360 plants in one plot. The trial lasts two years, one year of establishment where all the plants are watered the same amount, and year two when the irrigation treatments start. There are three different irrigation treatments, 80%, 50%, or 20% evapotranspiration (ETo) based on the Water Use Classification of Landscape Plants (WUCOLS). Each plant was randomly assigned a position in the plot and one of the three irrigation treatments. They were planted 2m away in each direction from their neighbor with their own irrigation drip ring so that the specific treatment was delivered to that particular plant. See below for more information on the irrigation setup.
Throughout the field season (June-September), monthly growth measurements and aesthetic ratings were recorded for each plant. These include length, width, height, foliage quality, flowering, disease resistance, pest tolerance, vigor, and overall appearance. Flowering and overall appearance ratings were assessed again two weeks after the initial monthly ratings to capture floral bloom times. Pictures of a representative plant per treatment per taxa were taken monthly to document growth and overall health over the field season. An open house was held at the end of the field season where landscape and horticultural professionals were tasked with evaluating the aesthetic qualities of a subset of the plants. In addition to measuring aesthetic ratings and growth, a certain subset of taxa was used to test physiological questions. More information on the physiological measurements can be found on the Physiology Page. This experimental setup was duplicated for plot two for the 2023 field season but with a different set of taxa.
Irrigation System Mechanics
Irrigation treatments were based on WUCOLS standards for high, medium, and low water use (80%, 50%, and 20% ETo). Evapotranspiration includes water evaporated from the soil and transpiration, which is water loss through plant leaves. Daily ETo and precipitation were recorded from the Washington Ag WeatherNet website because they have a weather station right next to the plots. These parameters, in combination with soil texture and soil water holding capacity, determined when the treatments needed to be watered. Tubing ran down each row of the plot, one tube per treatment, and was hooked up to one main pipe with an irrigation timer. Throughout the field season, the frequency of irrigation differed, but the volume of water applied to each plant in that irrigation event remained the same.
Field Seasons
2022 Irrigation Deficit Trial
15 taxa were evaluated during the 2022 irrigation deficit trial. Info on individual taxa is below, and the report from the 2022 field season can be accessed here: CRLP 2022 University of Washington report
Taxa Evaluated 2022
Results from 2022 UW open house
Favorite Taxa: Lagerstroemia Center Stage Red and Vitex Blue Diddley
We had 42 participants in our open house of varying backgrounds in the horticultural field from gardeners and landscape architects to researchers and public agency workers.
2023 Irrigation Deficit Trial
12 taxa were evaluated during the 2022 irrigation deficit trial. Info on individual taxa is below, and you can access the report from the 2023 field season can be accessed here: 2023 University of Washington Report.
Taxa evaluated 2023
Climate-Ready Vines Project
This project is a continuation of the Climate-Ready Landscape Plants Project which includes different irrigation regimes but also investigates the shading and cooling effects of vines. There will be 15+ taxa tested with five taxa common to all sites. This project will be conducted at five different field sites: the University of Washington, the University of California-Davis, South Coast Research and Extension Center, the University of Arizona, and Utah State University. Plot setup for this project is in progress with full installation of trellises and plants by summer 2023 with two seasons of deficit treatments in 2024 and 2025. Like the Climate-Ready Landscape Plants Project, plants will be rated on appearance qualities and growth. The plants will also be assessed on percent coverage of the trellis, and temperature through thermal imaging to access cooling potential.
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Want to get involved?
Climate Ready Landscape Plants is looking for volunteers to help with plot maintenance, upkeep and establishment. Please navigate to the UWBG Volunteer Website and submit an application to be a Climate Ready Landscape Plants Volunteer!