ASHS 2024 Conference

The Climate Ready Landscape Plants project evaluates the performance of plants exposed to three different deficit irrigation treatments in six climate zones. The experimental fields are completely replicated at all of the sites with plants spaced in a 2m x 2m layout, 8 replicates per treatment, up to 15 taxa tested per site, and irrigation based on reference evapotranspiration (ETo) with treatments of 20%, 50%, and 80% of ETo. Irrigation applications consist of a fixed volume of water depending on soil plant available water as determined by the US Geological Survey maps accessed via SoilWeb. The interval between irrigations was determined by accumulating daily ETo modified by the treatment factor. Irrigation occurred when the trigger value was attained. Plants were installed in the fall and irrigated with sufficient water for establishment during the first irrigation season and treatments were imposed during the second irrigation season. Monthly during treatment, 6 qualitative assessments of each plant were conducted and measurements in three directions were recorded to calculate a Plant Growth Index until the end of the treatment period that typically concluded in October. A substantial effort was made to ensure site-to-site consistency of the qualitative assessments by developing a ratings rubric and conducting frequent site visits with project management to “calibrate” site staff conducting the evaluations. Open House Field Days were conducted during the treatment season to which horticultural professionals and Master Gardeners were invited to evaluate the plants. This provided additional data and introduced the plants to potential users. This project started in 2004 as a graduate student research project, was expanded periodically at UC Davis, and then duplicated in 2017 at the UC South Coast Research and Extension Center in Irvine, CA as the University of California Landscape Plants Irrigation Trials™ (UCLPIT) project. With an award from the USDA Specialty Crops Multistate Program in 2019, the project was expanded to the University of Washington, Oregon State University, Utah State University, and the University of Arizona which facilitates the comparison of plant performance in response to deficit irrigation treatments across the western region of the U.S. The data collected leads to recommendations for irrigating those plants that are used by homeowners and landscape irrigation managers and assists landscape designers and architects designing landscapes that are water conserving and complying with California's landscape water conservation regulation, the Model Water Efficient Landscape Ordinance (MWELO).

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 Asclepias linaria ‘Monarch Magnet’, Dodonaea viscosa ‘Emerald Ice’, Eremophila glabra ssp. carnosa ‘Winter Blaze’, Ericameria laricifolia ‘Aguirre’, Hamelia patens ‘Sierra Red’, Leucophyllum frutescens ‘San Antonio Rose’, Leucophyllum langmaniae ‘Rio Bravo’, Tecoma ‘Red Hot’ and Rosmarinus officinalis 'Arp'. Irrigation did not affect plant growth of these nine taxa from April to October. Monthly visual quality assessment of some taxa was temporarily affected by irrigation, however, all performed acceptable or better at the low irrigation with the exception of Asclepias linaria ‘Monarch Magnet’ which had less than acceptable ratings in July and August for the low and high irrigation treatments. This taxa also had 62% mortality of plants under the high irrigation treatment between July and October. Hamelia patens ‘Sierra Red’ plants had frozen to the ground in winter 2022 and started to regrow in May. Five of the taxa (Dodonaea viscosa ‘Emerald Ice’, Eremophila glabra ssp. carnosa Winter Blaze, Ericameria laricifolia Aguirre, Hamelia patens Sierra Red, and Leucophyllum frutescens ‘San Antonio Rose’) maintained a high overall rating at the lowest irrigation treatment. Two field days were held in August and October 2022 where participants from the green industry and related sectors were invited to rate overall appearance, flowering and foliage of one representative plant from each taxa and irrigation treatment. Ratings from field day participants were similar to those from researchers during that month. Most participants’ favorite plants included the five taxa with consistently high overall ratings, only Dodonaea ‘Emerald Ice’ was among the top four favorites at both field days. All nine taxa tested 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.

To develop landscape irrigation recommendations, 22 taxa of landscape plants were evaluated under three levels of deficit irrigation in a field trial. The taxa consisted of common horticultural perennials and shrubs including multiple cultivars of Hibiscus syriacus, Nandina domestica, Rosa spp., and Salvia spp. Based on anticipated plant size and cultural requirements, taxa were planted in one of three adjoining fields, with each field laid out in a grid pattern with either 2 or 3 meter spacing between rows and between individual plants in each row. All fields were covered with a 2-3” layer of chipped bark mulch. For each taxon, 24 individuals were planted with eight replicates per irrigation treatment in a randomized complete block layout with both taxa and irrigation treatment being randomly assigned. Plants were installed in March as bareroot inputs, with containerized plants installed from April to early June of 2021. Daily reference evapotranspiration (ETo) values from a local weather station were obtained from the California Irrigation Management Information System. The amount of plant available water (PAW) for the trial site was obtained from the US Geological Survey via the Soilweb application. In 2021, plants were irrigated regularly to fully establish their root systems. From April to October 2022, plants were irrigated with one of three deficit irrigation treatments equal to 80%, 50%, or 20% of ETo. The treatments functioned similarly to a crop coefficient to modify daily ETo values. The modified ETo values were used to estimate when 50% of PAW was depleted for each treatment. 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 and length, width, and height measurements were collected to develop a plant growth index. 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.

Utah has experienced significant drought conditions, with 99.3% of the land under drought stress from the previous year to the present. In response to this challenge, deficit irrigation landscapes are gaining popularity in arid regions. This study aimed to investigate the overall appearance, plant growth, and physiological response of ten ornamental plants to deficit irrigation. The selected species include Caryopteris ×clandonensis ‘Blauer Splatz’ (Sapphire SurfTM bluebeard), Cercis canadensis (eastern redbud), Cercis occidentalis (western redbud), Cotoneaster ×suesicus ‘OSUCOT2’ (Emerald BeautyTM cotoneaster), Hesperaloe parviflora ‘Straight Up Red’ (‘Straight Up Red’ texas red yucca), Miscanthus sinensis ‘NCMS2B’ (bandwidth maiden grass), Physocarpus opulifolius ‘Diabolo’ (Diabolo® ninebark), Physocarpus opulifolius ‘Little Devil’ (Little DevilTM ninebark), Rosa ×hybrida ‘Meifranjin’ (Blushing Drift® rose), and Vitex agnus-castus ×rotundifolia ‘Helen Froehlich’ (Summertime BluesTM chaste tree). Eight plants per species were randomly assigned to one of three deficit irrigation frequencies, calculated based on 80% reference evapotranspiration (ETo) (high), 50% ETo (medium), and 20% ETo (low) at the Utah Agriculture Experiment Station’s Greenville Research Farm, North Logan, UT, USA. The overall appearance was evaluated biweekly, spanning from 30 Jun to 31 Oct 2023. Plant growth and stomatal conductance were recorded monthly during the growing season. The growth of plants was not significantly affected by reduced irrigation frequency. However, the impact of deficit irrigation on aesthetic performance and stomatal conductance was notable, particularly during August and September. The results highlight variability in plant performance across species, with Caryopteris ×clandonensis and Cotoneaster ×suesicus showing consistent performance across irrigation levels. However, Cercis canadensis and Physocarpus opulifolius ‘Diabolo’ exhibited a more pronounced difference under varying irrigation levels. Funding Source USDA Agricultural Marketing Service Specialty Crop Multi-State Program, USDA NIFA Hatch project UTA01666, 2022 Extension Water Initiative Grants Program, Utah State University’s Center for Water-Efficient Landscaping, and the Utah Agricultural Experiment Station

In response to recent revisions to the fertilizer ordinance in Hernando County, our research endeavors to delve into the attitudes and behaviors of residents towards fertilizer usage. With over 100 counties and municipalities in Florida implementing urban landscape fertilizer ordinances, Hernando County serves as a significant case study in understanding the dynamics of public perception and compliance. Our project employs a multi-faceted approach to gather comprehensive insights into resident perspectives. Tailored surveys have been developed to assess various aspects, including residents' knowledge of lawn care, familiarity with the county's fertilizer ordinances, current landscape conditions, and practices regarding fertilizer application. These surveys are being disseminated through diverse channels, encompassing social media platforms, the Hernando Extension networks, and Hernando County Utilities Department customers. Additionally, forthcoming focus group interviews will provide qualitative insights, offering a deeper understanding of community sentiments and the underlying factors shaping attitudes and behaviors. Through the integration of quantitative and qualitative data analysis, our aim is to gain a holistic understanding of the landscape of fertilizer usage in Hernando County. This entails not only identifying prevalent practices but also discerning the concerns and barriers faced by residents in adhering to the fertilizer ordinances. Such insights are pivotal in informing the development of targeted educational materials aimed at addressing community concerns, dispelling misconceptions, and providing practical guidance on responsible fertilizer usage. Our initial online survey revealed that 31% considered themselves very familiar with the Hernando County Fertilizer Ordinance, but 31% were not familiar with the details at all (n=383). Of these respondents, 73% care for their lawn and landscape themselves, with 11% using a professional service. Most residents responded that their lawn was fertilized at least once per year, with 18% saying that their lawn was never fertilized (n=844). Ultimately, the findings of our research hold significance beyond Hernando County, offering valuable lessons and strategies for promoting sustainable landscape management practices in similar contexts across Florida and potentially beyond. By fostering greater awareness, understanding, and knowledge of proper fertilizing practices, our project contributes to the broader goal of safeguarding water quality and environmental integrity for present and future generations.

Growing population, rapid urbanization and economic expansion have been raising the demand for fresh water. Additionally, climate changes, characterized by warmer temperatures, shifting precipitation patterns, and reduced snowpack are diminishing the water availability presenting new challenges for agricultural water use and conservation, particularly in the arid western states. One approach to addressing water scarcity involves inducing drought tolerance in crops. Plants exhibit physiological, morphological, and biochemical changes upon exposure to different wavelengths of light. This study focuses on determining the optimal ratio of blue to red light for inducing drought tolerance morphology in Zinnia elegans ‘Envy’. Seeds were sowed in Metro-Mix® 820 (SunGro Horticulture, Agawam, MA, USA) and kept on a misting bench. After germination, the plugs were exposed to full spectrum LED grow lights (ScynceLED, Mesa, Arizona) maintained at three ratios of blue and red light, 10:90, 25:75, and 50:50, controlled using a spectrometer (StellarNet Inc., Tampa, Florida, USA) in a covered chamber. The Photosynthetic photon flux density (PPFD) was maintained at 150 µmol.m-2.s-1 and the photoperiod was maintained at 12 hour dark and 12 hour light period. After four weeks of treatment, physiological and morphological parameters were measured in five destructively harvested plugs per treatment. The leaf number, growth index, and leaf area index showed no significant differences among treatments, however, the rate of assimilation and stomatal conductance were found highest under the 50:50 blue and red light ratio, compared to 25:75 but similar to 10:90. The total dry weight, leaf thickness, SPAD, and NDVI values were also higher at the 50:50 ratio, with total dry weight comparable to the 25:75 ratio. Subsequent irrigation treatments at 25% and 35% volumetric water content (VWC) were applied with the help of automated irrigation system using capacitance sensor, ECH2O 10HS (Meter Group, Pullman, WA, USA) to assess water requirements under different ratios of blue and red light suggesting a potential of these light treatments to reduce the Zinnia’s water needs.

Heat and moisture stress are increasing limitations to production of container-grown trees and growth of landscape trees, while reducing water use is an increasingly common goal. In two experiments, we investigated methods for reducing stress caused by limited water and extreme heat in container-grown tree seedlings in Aurora, Oregon. In the first experiment, we evaluated the potential for several ‘biostimulant’ or stress-tolerance inducing, soil-applied materials to improve growth of tree seedlings (Betula nigra) under limited water conditions. In the second experiment, we evaluated one of the most promising materials from that study in comparison to several other known or potential stress-reducing materials or techniques. In the first study, B. nigra seedlings were grown in pots with full water (determined by site evapotranspiration rate), one-half water, or one-half water with four different commercially available ‘biostimulant’ products that are marketed as inducing tolerance to moisture and heat stress in plants. Caliper growth, visual rating, and chlorophyll fluorescence values all showed that in the low-water groups, the plants treated with a mannitol plus calcium chelate product or a potassium phosphite product performed best and significantly better than the low-water control group. In the second experiment, over the course of two seasons we compared the effects of soil-applied potassium phosphite with other methods previously shown to reduce heat and/or drought stress. Abnormal extreme heat events, or ‘heat domes’, occurred during both growing seasons. Container-grown red maple (Acer rubrum) saplings were grown with moderate water and subjected to one of six treatments: untreated control, fresh-water misters triggered by preset ET value, kaolin foliar treatment, potassium phosphite soil application, propiconazole foliar treatment, and paclobutrazol foliar treatment. After two growing seasons, the mist treatment significantly improved growth compared to control plants while the potassium phosphite and kaolin treatments showed non-significant trends of improved growth. Based on these two studies, it is concluded that where possible, mist treatments during hot and dry conditions can improve container-grown tree seedling growth and condition, while potassium phosphite soil treatment and kaolin foliar treatments are likely to improve growth and condition in landscapes or where installation of misting apparatus is not feasible.

The UF/IFAS Florida-Friendly LandscapingTM (FFL) Program is Florida's premier Extension program for ecologically sustainable, science-based landscape practices that conserve water, protect water quality, and promote biodiversity. Since 1993, the FFL program has promoted water resource protection through both water conservation (water savings) and reducing non-point source pollutants (fertilizer nitrogen and phosphorus; pesticides) that may otherwise be carried into the state’s water bodies via runoff and/or leaching into groundwater. Despite longstanding promotion of FFL through Florida’s 67 county Extension offices, most Florida residents remain unaware of the program and its benefits. To promote public awareness of FFL, the program has undertaken a variety of marketing initiatives involving radio, television, social media, webinars, and online educational opportunities. On the radio, FFL produced a series of one-minute-long spots providing sustainable gardening tips. Called Florida-Friendly Landscaping in a Minute, the episodes aired twice each weekday on two NPR stations covering 19 northeast Florida counties. The daily listening audience was estimated at 4,600 for each airing, with 2.4 million total listeners each year. Webpage links to additional information back-up each episode. A wider audience was reached through the subsequent production of the Flip My Florida Yard television series. Produced in partnership with Crawford Entertainment with funding from the Florida Department of Environmental Protection, each 30-minute episode chronicles the complete makeover, or flip, of a homeowner’s typical Florida landscape into a more sustainable Florida-friendly landscape. All accomplished in eight hours, each episode features local designers and contractors and the local Extension agent, as well as a Maintenance Moment tip and a Yard Science segment featuring experts from UF/IFAS and other state entities. New shows air statewide on PBS and past episodes are streamed online. The program received a regional Emmy award in 2023. Flip My Florida Yard has been viewed more than 9.9 million times in the past year. FFL also recently hired a social media manager to increase FFL’s visibility on Facebook, Pinterest, Instagram, YouTube, and Linked-In. FFL’s social media reach is now growing exponentially. FFL also offers monthly webinars for both commercial and homeowner audiences. These webinars are archived to the FFL website and have accounted for more than 38,000 live and recorded views in the past year. Finally, the program has developed numerous online trainings and certification programs to help reach audiences at their convenience. As FFL begins its 32nd year, these marketing initiatives are helping it grow and reach new audiences.