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Interest Group Session: Climate Ready Landscape Plants
Thursday September 26, 2024 4:00pm - 6:00pm HST
Lehua Suite
The overall goal of this session is to highlight the latest advancements from the USDA Agricultural Marketing Service Specialty Crop Multi-State Program funded project titled “Climate Ready Landscape Plants”.

Coordinator/Moderator
  • Youping Sun, Utah State University, Department of Plants, Soils & Climate, Logan, Utah, United States
Speaker/Participant(s)
  • Jared Sisneroz, UC Davis
    Climate Ready Landscape Plants Trialed in Davis, CA
    Summary: To develop landscape irrigation recommendations, a field trial evaluated 22 taxa of landscape plants under three levels of deficit irrigation. Taxa included cultivars of Hibiscus syriacus, Nandina domestica, Rosa spp., and Salvia spp., among other common perennials and shrubs. Taxa were planted in a grid pattern with 2 meters spacing between rows and plants. Several larger taxa were planted in an adjacent field with 3 meters spacing. After an initial growing season of regular irrigation to establish the plants, from April to October 2022, plants were irrigated with one of three deficit irrigation treatments equal to 80%, 50%, or 20% of ETo. Treatments functioned like a crop coefficient in modifying daily ETo values. Irrigations occurred whenever this threshold was reached, with the volume of water applied being equal to 50% of PAW. The volume applied at each irrigation was constant across treatments with the frequency between irrigations varying by treatment. As a result, the 80% treatment was irrigated most frequently with the 20% treatment was irrigated thrice during the deficit period. Monthly during the deficit period, each plant was rated on six categories of aesthetic quality. Aesthetic performance between the treatments was compared using an ANOVA in conjunction with Tukey’s HSD post-hoc test in R. A majority of the taxa evaluated maintained acceptable aesthetic quality ratings on the lowest irrigation treatment. Two taxa evaluated, Lagerstroemia ‘SMNLCIBF’ Center Stage® Red and Rosa ‘ChewPatout’ Oso Easy® Urban Legend achieved high levels of aesthetic performance on the 20% treatment.
  • Amelia Keyser-Gibson and Soo-Hyung Kim, University of Washington, United States
    Variation in Landscape Plant Aesthetics, Growth, and Physiology to Deficit Irrigation Across the Western U.S. (20 mins)
    Summary: Climate change is causing more frequent and severe droughts in the Western U.S., while concurrently, about 70% of urban water use is dedicated to landscape irrigation. Therefore, water conservation techniques in the horticultural space, such as planting water-use-efficient landscape plants, will be essential to reduce irrigation consumption. Five different taxa, Hibiscus syriacus ‘Gandini Santiago’ Purple Pillar®, Hibiscus syriacus 'ORSTHIB5x1' PPAF, Rosa ‘Meibenbino’ Petite Knock Out®, Rosa ‘ChewPatout’ Oso Easy® Urban Legend®, and Vitex ‘SMVACBD’ Blue Diddley®, were subjected to one of three water deficit treatments in six sites: Tucson, Arizona; Davis, California; Irvine, California; Aurora, Oregon; Logan, Utah; and Seattle, Washington. Plants were rated on foliage quality, flowering, pest tolerance, disease resistance, vigor, and overall appearance. Growth measurements were also taken to calculate a plant growth index and relative plant growth index. Stomatal conductance and the efficiency of Photosystem II (ΦPSII) were measured when the treatments were in full effect and compared to the aesthetic ratings to get a broad picture of plant health. Overall, at individual sites, treatment did have a significant effect on aesthetic qualities and growth of specific taxa. Additionally, between sites, aesthetic qualities and growth differed significantly. Stomatal conductance and ΦPSII were not higher in the high treatment for all taxa and differed significantly between most sites. Additionally, higher gs and ΦPSII did not correlate with higher aesthetic ratings and growth. Our results highlight the importance of climate-specific plant selection for reducing landscape water use while achieving satisfactory aesthetic qualities and growth of landscape plants.
  • Ursula Schuch, University of Arizona
    Climate Ready Landscape Plants Trialed in Tucson, AR
    Summary: : Fifteen taxa of shrubs growing in a field in Tucson, Arizona were irrigated with three levels of irrigation based on local reference evapotranspiration (ETo) to assess growth and plant quality. Plants established during 2021 under 80% of ETo and in 2022 were irrigated at 20%, 50%, or 80% of ETo. Irrigation was applied 2, 9, and 15 times between April 1 and October 31, 2022, for the low, medium, and high irrigation, respectively. Best performing plants were Dodonaea viscosa ‘Emerald Ice’, Eremophila glabra ssp. carnosa ‘Winter Blaze’, Ericameria laricifolia ‘Aguirre’, Hamelia patens ‘Sierra Red’, Leucophyllum frutescens ‘San Antonio Rose’, and Tecoma ‘Red Hot’ which maintained a high overall rating at the low irrigation treatment. Irrigation did not affect plant growth of these taxa from April to October. Monthly visual quality assessment of some taxa was temporarily affected by irrigation, however, all performed acceptably or better at the low irrigation. Two field days were held in August and October 2022 where green industry professionals were invited to rate plant performance of one representative plant from each taxon and irrigation treatment. Most participants’ favorite plants included the taxa with consistently high overall ratings. The best performing taxa are low water use shrubs that can grow in the landscape with 20% of ETo in the low desert in Arizona. However, some may benefit from additional irrigation during the hottest time of the year for optimum performance.
  • Natalie Levy, South Coast Research & Extension Center, The University of California Agriculture and Natural Resources
    Climate Ready Landscape Plants Trialed in Irvine, CA
    Summary: As climate extremes, population growth, and agricultural/industrial water demands continue to increase, urban landscapes are an essential area where water conservation efforts must be improved. Deficit irrigation trials of ornamental plants began at the University of California, Davis (UCD) in 2004 and became the University of California Landscape Plant Irrigation Trials (UCLPIT™). In 2016, it was replicated at UC Agriculture and Natural Resources’ South Coast Research and Extension Center (SCREC) in Irvine, California. Researchers observed differences in performance between sites on selected taxa indicating that plant species will have irrigation requirements that vary in different climates. In 2019, the UCLPIT methodology was expanded to multiple western climate zones and soil types in Arizona, Utah, Oregon, and Washington through a USDA Specialty Crops Multi-State Program grant. Two seasons of data were collected in 2022 and 2023. The overall appearance and plant growth of 12 shared ornamental plants to deficit irrigation were investigated. Eight plants per species were randomly assigned to 1 of 3 deficit irrigation frequencies, calculated based on 80% reference evapotranspiration (ETo) (high), 50% ETo (moderate), and 20% ETo (low). Overall appearance and plant growth were evaluated monthly during April to October in both 2022 and 2023 at SCREC. There were variations in overall appearance across species under deficit irrigation in both years of the trial. Evapotranspiration rates were higher in 2022 and more irrigation events occurred for all treatments. The Philadelphus madrensis ‘ORSTPHILx2’ (Swan Lake® mock orange) and the Philadelphus lewisii 'Blizzard' (Blizzard mock orange) species evaluated in 2022 had significantly greater overall appearance on the moderate treatment than the low treatment.
Moderator
YS

Youping Sun

Dr. Sun is an Associate Professor of Landscape Horticulture whose research focuses on understanding the whole-plant response to water stress, with an emphasis on water conservation, and developing protocols to produce native plants. He is the principal investigator for the ‘Climate... Read More →
Speakers
JS

Jared Sisneroz

UC Davis
Mr. Sisneroz is the project manager of the UC Landscape Plant Irrigation Trials (UCLPIT) and the ‘Climate Ready Landscape Plants’ programs. He specializes in landscape plant water-use efficiency research and water resource management.
AK

Amelia Keyser-Gibson

University of Washington
SK

Soo-Hyung Kim

Dr. Kim is a Professor and Plant Ecophysiologist whose research focuses on how plants interact with their environment at the whole-plant scale. He is the principal investigator for the ‘Climate Ready Landscape Plants’ project at the University of Washington.
US

Ursula Schuch

University of Arizona
Dr. Schuch is a Professor and Extension Specialist in Environmental Horticulture in the School of Plant Sciences. Dr. Schuch’s research focuses on plant selection and management strategies to conserve water, maintain plant health, and aesthetic function. She is the principal investigator... Read More →
NL

Natalie Levy

Dr. Levy is an Associate Specialist for Water Resources at the South Coast Research and Extension Center. She specializes in landscape plant water-use efficiency research, water resource management, and water pollution prevention/mitigation.
Thursday September 26, 2024 4:00pm - 6:00pm HST
Lehua Suite
  Interest Group Session

Attendees (4)


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