ASHS 2024 Conference

Evaluation of Native Azaleas for Container Production in the Mid-Atlantic - William Errickson
Facilitating Pollinator Conservation in Agriculture: Understanding Grower Needs in Obtaining IPM Certification - Madison Love
Relationship between Soil Water Content, Quantum Efficiency, Stomatal Conductance and Stem Water Potential in Salvia guaranitica ‘Black and Blue’ - Lindsey Trinkle
Effect of Coconut Coir and Biochar Media on Ornamental Plant Growth and Nutrient Leaching - Saroj Burlakoti
Physiological and Morphological Characteristics of Marigold Exposed to Different Ratios of Blue Light and Red Light - Anju Chaudhary
Responses of Three Ornamental Species to Saline Water Irrigation - Zirui Wang
Field Performance of Penstemon Species under Deficit Irrigation - Zirui Wang
Responses of Calamagrostis ×acutiflora under Deficit Irrigation - Zirui Wang

Deciduous azaleas (Rhododendron spp.) are native to the Eastern United States and have potential for increased adoption in the ornamental nursery and landscape market. However, plant availability is currently limited and trials on the growth and performance of each species are lacking. Furthermore, seed propagation is the common production method for native azaleas, which can result in phenotypic variation and a longer period of time to produce a saleable product, relative to vegetative propagation. Under optimum growing conditions, native azaleas can be low-input plants with minimal insect and disease issues. However, they can also be susceptible to summer heat stress and require well-drained soils and partial-shade similar to their indigenous growing environments in order to thrive. To determine which species may be most well-adapted to typical container nursery production practices, container trials were established to evaluate nine different species of native azaleas, including R. arborescens, R. atlanticum, R. austrinum, R. canescens, R. cumberlandense, R. flammeum, R. periclymenoides, R. prunifolium, and R. vaseyi, grown in both full sun and 50% shade conditions. Seed-grown one-year old liners of each of the nine different species were established in one-gallon containers and evaluated for growth rate and physiological characteristics, such as leaf chlorophyll content and normalized difference vegetation index (NDVI), comparing plants grown in full sun vs. 50% shade. In year two, bloom dates and number of blooms per plant in full sun vs. 50% shade were compared. R. atlanticum demonstrated the greatest potential for commercial production, especially when grown under 50% shade conditions, based on growth rate and average number of blooms per plant. These results suggest that R. atlanticum may be a reliable species of native azalea for growers to commercially produce for this growing market segment, while other species may still have potential, albeit with additional attention to their specific production requirements.

Due to global concerns over the decline in pollinator populations, Walmart U.S. has initiated a policy requiring all produce and floral products sold in stores to be sourced from vendors who have obtained an Integrated Pest Management (IPM) certification from an approved third-party organization by 2025. The certification process for growers entails comprehensive documentation of operational practices, pesticide use and mitigation, and evaluation of on-farm pollinator habitat. However, this process is cumbersome for growers to conduct alone, necessitating assistance from a third-party such as Extension agents and staff. Furthermore, identifying and expanding existing pollinator habitat is often unfamiliar to growers, presenting a significant barrier in the application process and hindering the expansion of pollinator habitat. This project seeks to assess the needs of growers in navigating the IPM certification process and understanding the barriers they face. Future work will include the development of accessible consulting services that supports North Carolina growers throughout the certification process while also equipping them with necessary skills and knowledge to enhance and expand pollinator habitat.

Perennials are an important component in north-central Texas landscapes, providing color and foraging for local pollinators. However, severe summer drought and a rapidly growing urban environment forces limitations on water availability for landscape irrigation. Therefore, we need to evaluate the impact of deficit irrigation on landscape plant performance. Salvia guaranitica ‘Black and Blue’ is a perennial known to perform well in north-central Texas summers, and it attracts numerous pollinators, including bumblebees, butterflies, and hummingbirds. Twelve beds were created in four blocks, with three beds per block and one plant planted per bed. Within each block, irrigation was applied at one of three levels, 60% of evapotranspiration (ET), 30% of ET and no irrigation. Soil moisture monitors [time domain reflectometry (TDR), 10HS, Onset Computer Corp., Bourne, MA] and a handheld moisture meter (TDR, Fieldscout 350, Spectrum Technologies, Aurora, IL) were used to measure water content by volume (Θv). Quantum efficiency (ΦPSII) and stomatal conductance (gs) were measured using a fluorometer/porometer (LI-600, LiCor Corp., Lincoln, NE), and stem water potential of each plant was measured using a pressure chamber (Model 615, PMS Instrument Company, Albany, OR) on a weekly basis. Surprisingly, soil moisture levels in the 30% treatment (0.10 m-3·m-3) were the lowest, with 60% at 0.25 m-3·m-3) and no irrigation at 0.14 m-3·m-3. Quantum efficiency was similarly lower in 30% (0.60), compared to 0.72 and 0.69 for the 60% and unirrigated plots, respectively. Stomatal conductance was similar across all treatments. Stem water potentials were highest in plants receiving 30% (800 kPa), compared to 380 kPa in 60% and 360 kPa with no irrigation. Across all treatments, plant performance was correlated to soil water content, (ΦPSII P=0.03, r=0.24; gs P=0.05, r=0.22; kPa P=0.003, r=-0.33). Based on this study, Salvia guaranitica ‘Black and Blue’ should be irrigated at 60% of ET for best plant performance during summer heat and drought.

The growing demand for container ornamental plants opens new opportunities for nurseries to expand their business. However, expecting to improve plant quality, growers often overapply fertilizer and water. Excessive fertilizer application and overwatering can result in nutrient leaching and runoff. In addition, growers heavily rely on unsustainable sphagnum moss as a medium for growing their plants. Replacing sphagnum moss with coconut coir may increase production sustainability, and incorporating biochar may have potential to adsorb excess nutrients, thus lowering fertilizer concentration in leachate. In this study, we explored the suitability of using various mixtures of coconut coir and biochar for growing goldenrod, lavender, and chrysanthemum plants for two growing seasons. Results indicated that utilizing pine bark and coconut coir did not hinder plant growth and development compared to a traditional mixture of pine bark and sphagnum moss for any of the plants studied. Also, inclusion of 10% biochar did not enhance growth, nor did it reduce nitrate nitrogen and phosphorus concentration in container leachate. Biochar did not reduce nutrient leaching in this study. However, coconut coir was found to be a suitable substitute for sphagnum moss in container nursery production.

Light plays a crucial role in regulating various aspects of plant growth, development, and metabolism. The absorption spectra of photosynthetic pigments are primarily concentrated in the blue (400-500nm) and red (600-750nm) regions of light, making these wavelengths particularly influential in plant morphogenesis and photosynthesis. Varying the ratios of blue to red light can produce distinct morphological and physiological outcomes in plants. Blue light enhances photosynthetic activity and promotes more compact and robust growth, while red light encourages rapid growth and flowering. These specific combinations can be optimized for desirable traits in ornamental plants. This research aims to evaluate the effects of different combinations of blue and red light on the physiological and morphological characteristics of marigold (Tagetes erecta) ‘Crackerjack’. Seeds were sowed in Metromix 820 potting mix and placed on a misting bench for germination. After germination, seedlings were subjected to three different light spectra: 10% blue and 90% red LEDs (10¬B90R), 25%blue and 75% red LEDs (25B75R), and 50% blue and 50% red LEDs (50B50R) maintained using a spectrometer (StellarNet Inc.). A 90% shade cloth was used in each treatment to prevent the effect of outside light. The photosynthetic photon flux density (PPFD) was maintained at 150 µmol.m-2.s-1 and the photoperiod was maintained at 12 h light and 12 h dark. After four weeks, various physiological and morphological parameters were assessed in five destructively harvested seedlings per treatment. We found that seedlings grown under the 25B75R treatment exhibited greater height in comparison to those under the 50B50R spectrum but similar to seedlings under 10¬B90R. Stomatal conductance (gs) and photochemical efficiency (Fv/Fm) were higher under 50B50R than in 25B75R but comparable to those in 10¬B90R. Additionally, the SPAD and NDVI values, which indicate chlorophyll content and overall plant health, were highest under the 50B50R treatment. However, leaf area, total fresh weight, and total dry weight showed no significant differences among the treatments.

Deficit irrigation plays a crucial role in water conservation in urban landscapes. Calamagrostis ×acutiflora (feather reed grass) is an ornamental grass known for its neat clumps, golden plumes, and fast growth. It is gaining popularity in urban landscapes across arid and semi-arid regions in the United States. However, little is known about its responses to deficit irrigation. A field study was conducted in 2022 and 2023 at the Utah Agricultural Experiment Station’s Greenville Research Farm in North Logan, UT, to assess the effect of irrigation frequencies on the growth of feather reed grass. Reference evapotranspiration (ETo) data from a weather station in the Utah AgWeather System, Utah Climate Center, Logan, UT, was used to determine the irrigation frequency for each treatment. Four hundred plants were transplanted into the field plot, with twenty plants in each of the twenty 2 by 2-meter plots. Eighty plants within four plots were randomly assigned to one of five irrigation treatments, controlled based on 80%, 60%, 40%, 20%, and 0% ETo. Two harvests were conducted on 30 Sep 2022 and 3 Nov 2023, during which plant height, number of tillers, and biomass were recorded. Plants height, number of tillers, and biomass for both years exhibited a linear and quadratic increase as the irrigation frequencies increased from 0% to 80% ETo. In addition, the linear relationship between irrigation treatments and grass height became less distinct in 2023, although grasses irrigated at 80% ETo were taller compared with those at lower irrigation levels. Based on the results, an irrigation frequency of 40% to 60% ETo is recommended for feather reed grass to maintain optimal growth.

Water-efficient landscaping can reduce water consumption without compromising the aesthetical appearance of urban landscapes. Penstemon, with more than 250 species available in a spectrum of colors, is a popular choice in xeriscape designs and water-wise gardening due to its ability to thrive in dry conditions while providing attractive visual appeal. However, limited field trials have explored the responses of penstemon under deficit irrigation. This study, conducted at the Utah Agricultural Experiment Station’s Greenville Research Farm, North Logan, UT, USA, from 30 Jun to 31 Oct 2023, was to investigate the overall appearance and canopy temperature responses of three penstemon species: Penstemon barbatus (Cav.) Roth ‘Novapenblu’ (Rock CandyTM blue penstemon), Penstemon pinifolius (pineleaf beardtongue), and Penstemon strictus (rocky mountain beardtongue), under three irrigation frequencies. Reference evapotranspiration (ETo) was utilized to control irrigation frequencies. Eight plants of each penstemon species were randomly assigned to one of three deficit irrigation treatments, calculated based on 80% ETo (high), 50% ETo (moderate), and 20% ETo (low). A monthly evaluation of overall appearance was conducted. Top-view infrared images of plant canopies, from which canopy temperature can be calculated, were captured using a thermal camera. Results revealed that higher irrigation frequency led to better overall appearance, with some variability observed among species and months. Moreover, increased irrigation frequency correlated with lower canopy temperatures, displaying species-specific responses. Further observation is needed to compare the responses of P. strictus, P. pinifolius, and P. barbatus under field conditions.

Water scarcity is a pressing issue in Utah and the Intermountain West, leading to a growing interest in exploring alternative water sources for landscape irrigation. However, alternative water often contains elevated levels of salts, such as sodium chloride (NaCl), which can negatively impact plant growth and appearance. This study investigated the effect of saline solutions on the aesthetic value, growth, and stomatal conductance of three ornamental species: Hibiscus syriacus ‘JWNWOOD4’ (Pink Chiffon® rose of sharon), Viburnum carlesii ‘Spiro’ (koreanspice viburnum), and Vitex agnus-castus ‘SWVACSD’ (lilac chastetree). Plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 0.9 dS·m-1 and saline solutions at 5.0 or 10.0 dS·m-1 for eight weeks. Visual quality was rated weekly using a reference scale ranging from 0 to 5 (0 = dead, 5 = excellent without foliar salt damage). Half of the plants per treatment per species were destructively harvested on 16 Aug (first harvest), and the remaining plants on 4 Sep (second harvest). Plant growth parameters and stomatal conductance were recorded at harvests. Foliar salt damage, such as leaf discoloration and necrosis, was prominently observed in plants, particularly in Viburnum carlesii subjected to elevated EC irrigation. Higher stomatal conductance was consistently observed in all plants irrigated with nutrient solution compared to those under saline irrigation. Interestingly, the salinity treatment did not significantly affect the growth of Vitex agnus-castus, indicating its high salt-tolerance. Notably, Viburnum carlesii displayed higher sensitivity to salinity stress compared to the other two ornamental species. These findings highlight significant variations in responses among the ornamental plant species under saline irrigation at varying EC levels, emphasizing the necessity of employing appropriate alternative water usage strategies.

Sponsoring Professional Interest Groups
Technology: Coordinator Milt McGiffen - milt.mcgiffen@ucr.edu
Teaching Methods: Coordinator, Kathryn Orvis – orvis@purdue.edu
Controlled Environment: Coordinator, Kent Kobayashi - kentko@hawaii.edu

Supporting Professional Interest Groups
Federal Partners: Matthew Mattia - Matthew.Mattia@usda.gov
Plant Biotech: Kedong Da - kda@ncsu.edu
Ornamentals/Landscape and Turf; Youping Sun - youping.sun@usu.edu
Local Food Systems: Charles H. Parrish II - chip.parrish@pm.me

Artificial intelligence and related topics, e.g., robotics, have been a long time coming in agriculture. For decades there have been predictions of intelligent robots replacing humans, and large farms run by a few humans with many autonomous tractors and other devices. But with the now widespread use of artificial intelligence in everyday life,
the moment has arrived. We developed this colloquium by casting a wide net out to all the Professional Interest Group Chairs, and have assembled talks and demonstrations from general topics to specific applications.

Two online meetings were held, where Professional Interest Groups officers and those interested suggested speakers and discussed topics. Further discussions over email helped fill in the details to create this colloquium.

We will have a block of speakers for the diverse topics we present below, as well as panel discussions on how AI is and can be incorporated into various aspects of Horticulture, so that there is ample time for questions and discussion.

Title: Overview of the Colloquium

Speaker: Milt McGiffen, Cooperative Extension Specialist, Department of Botany and Plant Sciences,
University of California, Riverside, CA.

AI in Ornamentals

Title: FloraCount: An App for Rapid Assessment of Pollinator Attractiveness to Annuals and Perennial Plants.

Description: Customers are interested in buying annuals and perennials that support pollinators. Protocols for rapid assessment in flower trail evaluations are not available. We have developed a mobile app that can be used to analyze in real time the users’ observational data and quantitatively rank the relative utility of observed cultivars to pollinator communities. This app takes into account pollinator groups, relevant floral characteristics and landscape.

Presenter: Harland Patch
Assistant Research Professor
Department of Entomology
Penn State University
549 Ag Sciences & Industries Building
University Park, PA 16802

Title: Approach to Biodiversity Protection: Employing AI and IoT Systems for the
Containment of Box Tree Moth Proliferation.

Description: The box tree moth (BTM, Cydalima perspectalis) is an invasive pest first confirmed in Niagara County, New York in 2021. This invasive pest can significantly damage and potentially kill boxwood (Buxus species) plants if left unchecked. This presentation describes our advances in combining deep learning algorithms for enhanced computer vision with IoT-enabled smart traps, to facilitate the early detection and continuous monitoring of BTM populations and to protect the prevalent ornamental boxwood in U.S. landscapes.

Presenter: Yanqiu Yang (she/her)
Ph.D. Graduate Research Assistant
Department of Agricultural and Biological Engineering
Pennsylvania State University
3 Agricultural Engineering Building
University Park, PA 16802

Title: Landscapes from Words: The Future of Landscape Design with AI.

Description: The ongoing text-to-graphic artificial intelligence (AI) revolution has the potential to change the field of Landscape Architecture dramatically. The ability to produce original high-quality graphics, manipulate the viewer's perspective of images, and amend the rendering style through text inputs are significant advancements that will
inform new design process models. These changes can lead to expanded design exploration, improved accessibility for non-designers to contribute to creating visual concepts, enhanced ability to integrate data analysis and visualizations, and streamlined collaboration between clients and project stakeholders using a shared visual language. This talk focuses on two dimensions of change that may result from the rapid evolution of text-to-graphic AI, including (1) faster iterations and exploration of design options and (2) the advancement of methods that result in more inclusive and responsive design. In the classroom, students are just beginning to acknowledge the existence of text-to-graphic AI, which allows them to experiment with text-based design options that allow them to quickly visualize and explore a wide range of site program alternatives. Nevertheless, how do we manage the ethical and creative boundaries within an academic setting? In a research context, methods supporting rapid manipulation of both generated images and existing landscape photography represent advances that allow for greater collaboration surrounding landscape design decisions (Incorporating resilience strategies, protecting vernacular landscape elements that support a sense of place, or representing new design proposals that modify the landscape). These approaches allow stakeholders to gain remarkable advances in influencing the design process through shared visualization development. However, as with any emerging technology, practitioners, educators, and researchers need to respond to the challenges presented by text-to-graphic AI by developing and testing new design process models and public engagement techniques that can improve landscape decision-making and streamline collaboration.

Presenter: Aaron Thompson
Assistant Professor
Department of Horticulture and Landscape Architecture
Purdue University
625 Ag Mall Drive
West Lafayette, IN 47906

Title: Developing Guidelines for Extension’s Use of ChatGPT and Other Generative AI
Tools.

Description: A new technological era marked by the advent of Artificial Intelligence (AI), particularly generative AI and Large Language Models (LLMs) like ChatGPT has necessitated the need to navigate this domain with a compass of ethicality, safety, and effectiveness. Penn State’s experience developing guidelines for Extension’s use of
generative AI tools which will be shared and discussed.

Presenter: Michael Masiuk
Assistant Director – Horticulture Programs
Penn State Extension
342 Agricultural Administration Building
University Park, PA 16802

Panel: 30 minute panel with the above speakers, to allow time for Q&A and discussion.