ASHS 2025 Conference

A forum for discussion of potential collaborations with regards to ornamentals – i.e. floriculture, nursery crops, breeding, turf, ornamentals industry, botanic gardens, landscape industry, orchids, etc.

Characterizing phenotypic variation in Ratibida columnifera (Nutt.) Woot.

Due to low annual precipitation and high elevation, many residential areas in the Intermountain West region are classified as high-elevation deserts, necessitating the incorporation of drought-tolerant plants in residential landscapes. However, due to the short growing season and low winter temperatures, many commercial water-wise plants often fail to thrive in this region. Native plants from the Intermountain West could serve as low-water-use landscaping alternatives, but their drought tolerance remains unclear. The objectives of this study were to determine the effects of decreased medium volumetric water contents on the plant growth and physiology of four native ornamental plant species, including Asclepias speciosa (showy milkweed), Hedysarum boreale (Utah sweetvetch), Penstemon eriantherus (fuzzytongue penstemon), and Penstemon grandiflorus (shell-leaf beardtongue), in a greenhouse. Twenty-four plants of each species were randomly assigned to an automated irrigation system, and the substrate volumetric water content was maintained at 0.40 (control) or 0.20 m3⋅m−3 (drought) for 50 days. The decrease in substrate volumetric water content resulted in increased proportion of leaves visibly wilted across the four plant species and also impaired their visual quality. However, H. boreale, P. eriantherus, and P. grandiflorus receiving drought treatment where the substrate volumetric water content was 0.20 m³·m⁻³ still showed acceptable visual quality, while A. speciosa exhibited an unacceptable visual quality. However, the reduction in substrate volumetric water content from 0.40 to 0.20 m³·m⁻³ decreased relative plant growth index of A. speciosa and H. boreale by 19% and 17%, respectively, at the termination of the experiment. In addition, the total leaf area of H. boreale, P. eriantherus, and P. grandiflorus decreased from the control to the drought treatment, while the drought treatments reduced the dry weight of leaves of A. speciosa, H. boreale, and P. grandiflorus. To acclimate to the drought stress, A. speciosa and H. boreale modified their specific leaf area. In addition, H. boreale also increased its root to shoot ratio to adapt to water stress. Drought stress impaired the visual quality and growth of all four high-elevation desert ornamental species in this research. Penstemon eriantherus and P. grandiflorus maintained better visual quality and growth, making them more suitable for low water-use landscaping. Asclepias speciosa showed greater sensitivity to reduced water content despite its morphological adaptations to drought.

Warm-season (C₄) turfgrass species such as bermudagrass (Cynodon spp.) and zoysiagrass (Zoysia spp.) exhibit superior recuperative potential compared to cool-season species. Excessive divot injury on cool-season turfgrass tees during peak golf play in summer can be problematic in Chicago, IL. Newer bermudagrasses and zoysiagrass are adaptable to northern climates, given improved cold tolerance. Improved cold tolerance and recuperative potential of newer bermudagrass and zoysiagrass suggest their possible use as a golf tee surface in temperate regions. This study evaluated newer cold-tolerant warm-season cultivars for use on golf course tees and was conducted in Lemont, IL. The RCBD study utilized eight treatments with five replications. Treatments included four bermudagrass cultivars (Tahoma 31, OKC3920, OSU15x9, OSU1629) and four zoysiagrass cultivars (Meyer, Innovation, DALZ1701, DALZ1808). Area Under the Progress Curve (AUPC) was used to integrate seasonal performance across timepoints. Bermudagrass entries Tahoma 31, OKC3920, and OSU1629 demonstrated significantly superior establishment rates, lateral spread, and turfgrass cover. In 2024, average turfgrass cover for the four bermudagrasses was 60% versus 21.1% for the four zoysiagrasses. All bermudagrasses retained acceptable green color ratings (≥6) by mid-October, with OSU15x9 showing extended fall green color retention. Meyer and DALZ1808 zoysiagrass were the earliest to break dormancy on Apr 29, 2025. Continued evaluation of cold-tolerant warm-season turfgrasses for winter survival is necessary prior to their use in northern climates.

The effects of planting trees at improper depths have been clearly identified for many species. Improper planting often leads to reduced growth, reduced aesthetic value and increased mortality. Magnolia grandiflora is an evergreen species native to coastal states from North Carolina, south to Florida and west to Texas. The cultivar 'Kay Parris' is gaining popularity and is widely cultivated in the southeastern U.S. for its compact form and beauty in the landscape. On 18 December, 2023, asexually propagated 'Kay Parris' magnolia in 8.7L containers were transplanted to a field in Nacogdoches, TX. Plants were randomly assigned one of four planting depths (crown 5 cm above grade, crown planted at grade, crown 5 cm below grade and crown planted 10 cm below grade) and one of two mulching treatments (7.6cm of mulch applied or no mulch). Plants were randomly arranged in a modified complete block design comprised of 3 blocks with 2 plants of each treatment combination in a block. Dimensions of each plant (including height and width in two directions) were recorded at planting and ornamental ratings were assigned. After one year of establishment, the only statistically significant difference among the treatments was that those plants that received a mulch application grew taller than those with no mulch by over 7cm. No other statistical differences appeared in year one of the study. Year two of the study is ongoing.

High diversity seed mixes have potential for providing ecological benefits including improvement of soil health, support of pollinator populations, and providing low maintenance landscaping. The focus of this research is to evaluate perception of the general public on the aesthetic value and desirability of diverse seed mixes in various settings. An online survey was deployed which included imagery of diverse seed mixes and conventional landscapes. Respondents were asked to rate desirability of the use of diverse seed mixes in various potential areas including home gardens, low traffic public spaces, and vacant lots. Respondents were also asked to evaluate the perceived ecological services associated with diverse seed mixes. Of respondents, 42 percent found diverse seed mix plantings appealing, compared to 52 percent who expressed that a conventional landscape was appealing. Greatest support for application of diverse seed mixes was for use in private gardens, vacant lots, and community garden spaces. Among respondents, enhancing appearance and support for pollinator populations were rates of highest importance in terms of landscaping benefits.

Water use in the landscape has become a more prevalent issue as the demand increases for more residential and commercial areas to be irrigated. This increase in water use indicates a need for drought tolerant plant species. Ornamental ground covers may provide an alternative to traditional turfgrass and provide water savings. Several studies have evaluated drought tolerance of turfgrass species, including Poa pratensis and Festuca arundinacea. Ground cover species, however, have less research available regarding drought tolerance. In this study, we analyzed six ground cover species (Dianthus caryophyllus, Lysimachia nummularia, Phlox subulata ‘Emerald Blue’, Sedum album, Stachys byzantina, and Vinca major) and three turfgrass species (Bouteloua dactyloides, Festuca arundinacea, and Poa pratensis) to evaluate their performance during drought and recovery. We conducted two studies to simulate drought-like conditions in a greenhouse at Kansas State University from April 2024 to November 2024 and May 2024 to January 2025. During the dry downs, plants were not watered until they reached a quality rating of one (1-9 scale, 1=dead/dormant and 9=best quality). Following the dry downs, normal watering resumed for 60 d to simulate a recovery period. Data collected three times per week during the drought period included quality rating (1-9), pot weight (g), and volumetric water content (θv); and one time per week we collected leaf water potential (ΨLeaf) and stomatal conductance (gs) readings. Results show S. album performed the best lasting an average of 157 d until reaching a quality rating of one. S. byzantina, B. dactyloides, V. major, D. Caryophyllus also performed well averaging 92, 51, 46, and 40 d, respectively, to a quality of one. P. subulate, P. pratensis, F. arundinacea, and L. nummularia performed the worst, averaging 35 d to decline to a quality rating of one. Following the dry down, the 60 d recovery period showed the following species recovered: B. dactyloides [58% Percent Green Cover (PGC)], F. arundinacea (45% PGC), L. nummularia (14% PGC), S. album (11% PGC), P. pratensis (10% PGC), and V. major (5% PGC). None of the other species recovered through the recovery period. Results indicate S. album, B. dactyloides, and V.major may perform the best in landscapes experiencing drought. F. arundinacea, L. nummularia, and P. pratensis may be good options as well if rain events or irrigation resumes following a dry or dormancy period.

The American Rose Trials for Sustainability® (A.R.T.S.®) program trials roses throughout the US and is in its ninth year of announcing winning roses. Roses are evaluated monthly during the growing season for floral attributes (42.5% of score), foliar health and quality (45% of score), and growth habit (12.5% of score). Over the two-year trial, roses are grown using minimal inputs (i.e. no pesticides, no deadheading, moderate irrigation, etc.). Entries that score equal to or higher than the regional average of the control cultivars (Double Knock Out® [‘RADtko’] and Sunrise Sunset™ [‘BAIset’]) and have >50% survival by the end of the trial period, earn Local Artist awards based on Köppen climate region. Roses winning in four or more regions earn the added distinction of the Master Rose award. The 2026 award winning roses were trialed in 2023 and 2024. Six US Köppen climate regions were represented (Cfa, Cfb, Csa, Dfa, Dfb, and H) . Three roses won 2026 A.R.T.S.® Master Rose awards: Dessert First™ ('DD987-1'; Csa, Dfa, Dfb, and H), Ruby Red™ ('MEIzilena'; Csa, Dfa, Dfb, and H), and Blushing Drift® ('MEIfranjin'; Cfa, Cfb, Dfa, Dfb, and H). Eleven roses won 2026 A.R.T.S.® Local Artist awards: Celeste BlueSky™ ('P2046L'; Csa and Dfa), Easy Spirit™ ('WEKmereadoit'; Csa and H), Elizabeth® (AUSMajesty'; Cfa and Csa), Julie Andrews ('DELfluros'; Dfa), Maurice Utrillo™ ('DELstavo'; Csa), Patriot Dream™ ('BAIdre'; Dfa), Reminiscent® Coral ('BOZfra221'; Dfa), Ringo® Double Pink ('CHEWDelight', Csa abd Dfa), True Confidence™ ('FS118T'; Dfa), True Crush™ ('ESR015T'; Dfb), and White Lies™ ('POT3', H). Performance data will be provided by region for the two control and fourteen winning rose cultivars.

Establishment of bentgrass (Agrostis stolonifera) from seed in sand-based systems using subsurface drip irrigation (SDI) presents a challenge due to limited capillary rise of water from the drip emitter. An experiment was designed to evaluate bentgrass seed irrigated overhead at establishment and then transitioned to SDI once roots reach specific depths. Treatments consisted of a control (overhead irrigation only) and SDI irrigated overhead till roots reached 0, 5, 10 and 15 cm depth. Nineteen-liter (5 gallon) buckets (lysimeters) were filled with 5 cm of pea-gravel and then 30 cm mix of sand 90% and peatmoss 10%. Each bucket had a single drip emitter (gallon/hour) in the center of the bucket at a 15 cm depth. Data consisted of days to reach transition depth, percent cover, soil moisture and nitrogen. The SDI at 0 cm rooting depth treatment never established any bentgrass as irrigation from the emitter never reached the surface. The 5, 10 and 15 cm SDI treatments transition from overhead to drip 18, 27 and 38 days after seeding, respectively. The percent cover was 100, 82, 85 and 95% for the control 5, 10 and 15 cm treatments, respectively at 90 days after seeding. Volumetric water content was highest in the control and lower in the SDI treatments regardless of treatment. The SDI irrigation treatments developed tissue desiccation on the perimeter of the bucket after transitioning as the lateral capillary movement of water failed to reach the width of the bucket. Further research is needed to evaluate SDI spacing during transitioning that produce a high quality turfgrass in sand-based systems.

This project is focused on improving nutrient management recommendations for sod producers as part of Florida’s best management practices (BMPs) program. The goal of this project is to evaluate nitrogen (N) fertilizer rate recommendations for Florida sod growers to achieve yield goals (shorten time to harvest) without negatively impacting water quality. The project was initiated in October 2023 and was conducted at four sod farms across the state and at the West Florida Research and Education Center (WFREC). At each farm, the project was conducted on two grass species. The N fertilizer (70% soluble plus 30% slow release) rates included 0, 120, 190, 260, and 330 lbs N/acre/year, which includes the range of current University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) recommendations. The annual N rate was split into monthly applications throughout the growing season. At the WFREC location, N applications were also being combined with phosphorus (P) fertilizer applications at 0 and 44 lbs P/acre/year to determine both N and P leaching. The treatments were arranged in a randomized complete block design with four replications. All other normal agronomic practices (irrigation, pesticides, etc.) were followed. Data collection included monthly visual turfgrass quality ratings, visual estimated percent cover, percent green cover via digital image analysis, and normalized difference vegetation index (NDVI). Soil cores and tissue samples were collected at the beginning and end of each growing season to determine soil chemical properties and nutrient concentrations. At harvest, sod samples were also collected to measure nutrient exports from fields. At WFREC, leachate was collected weekly and as needed based on rainfall events. Leachate volumes were measured at each water sampling event and subsamples from the leachate were analyzed for N and P concentrations. Preliminary results indicate that there are treatment differences in percent cover for all grasses. When grass species was combined across sod farms, the N rates of 260 and 330 lbs N/acre/year increased St. Augustinegrass [Stenotaphrum secundatum (Walter) Kuntze] percent cover. Additionally, the yearly rate of 330 lbs N/acre resulted in the greatest bermudagrass percent cover [Cynodon dactylon (L.) Pers. x C. transvaalensis Burtt-Davy]. This experiment is being repeated, and additional analysis will occur after the second harvest cycle has been completed.