ASHS 2025 Conference

Cultivar trials are important to ensure that growers have up-to-date information on crop performance, including yield, disease and insect resistance, environmental adaptation, and quality for their region. Crops with lesser planted acreage are often overlooked, as cultivar trials can be expensive, time consuming, and labor intensive. Winter squash is commonly grown in Tennessee and North Carolina, with over 300 and 700 acres grown, respectively; however, there is little cultivar trial information available for many types of winter squash, such as delicata squash. Delicata squash (Cucurbita pepo ssp. texana) is a winter squash originating from North and Central America. This squash can have a vining or bush habit and typically cylindrical fruit that is buff color with green stripes. It is a customer favorite due to its thin, edible skin, for which it’s named, and sweet flavor. The objective of this trial was to compare the yield, fruit characteristics, disease resistance, and storage life of 10 cultivars of delicata squash. The cultivars evaluated were: ‘Bush Delicata,’ ‘Sweet Dumpling,’ ‘Sugar Loaf,’ ‘Honey Boat,’ ‘Candystick Dessert,’ ‘Zeppelin,’ ‘Jester,’ ‘Delicata JS,’ ‘Sweet Lightning,’ and ‘Ugly Dumpling.’ The trials were conducted in Crossville, TN and Waynesville, NC. Squash were direct seeded in 18-foot plots with 3 feet between plants and 6 feet between rows, with four replications per cultivar. Powdery mildew was rated on a 0-5 scale with 0 indicating no powdery mildew and 5 indicating that all plants were symptomatic. Yield calculations were based on 2,418 plants per acre. ‘Delicata JS’ had the highest yield (15,500 lbs. ac-1) and most marketable fruit but also had the highest number of unmarketable fruit. ‘Ugly Dumpling’ also had a high yield but had the highest incidence of powdery mildew. ‘Zeppelin’ had the lowest incidence of powdery mildew. All cultivars tested had a shelf-life of four weeks in cold storage.

Spring broccoli production in the southeastern and mid-Atlantic United States has become increasingly vulnerable to high temperatures and variable rainfall. To address this challenge, a multistate trial was conducted to evaluate the performance of eight broccoli cultivars across seven states (NC, VA, GA, AL, MA, MI, IN). The objectives were to assess plant growth and yield performance under heat stress and to determine cultivar-specific normalized difference vegetation index (NDVI) thresholds that could predict marketable yield. Each trial site implemented a completely randomized block design with four replications and standardized plot dimensions (30 plants per plot in double rows on black plastic mulch). Fertility and irrigation were managed according to site-specific recommendations and monitored through soil testing and evapotranspiration estimates. UAV-based RGB and multispectral imagery was collected biweekly (4–12 weeks after transplanting) at midday under clear-sky conditions. Soil samples, weather data, and pest control measures were recorded at each location. Results showed that each cultivar exhibited a distinct NDVI profile correlated with crown greenness and morphology. Cultivars such as ‘Eastern Magic’ and ‘Green Magic’ maintained acceptable head quality and yield despite elevated temperatures, suggesting suitability for late spring planting. The use of NDVI imaging proved to be a promising tool for identifying cultivar vigor and optimizing management decisions during periods of heat stress.

Current fertilization guidelines for peach production, established decades ago, are gradually being revisited due to emerging challenges – such as rerising fertilizer costs, nitrate leaching, excessive vegetative growth, and declining fruit quality. These guidelines recommend nitrogen applications of 67.25–78.5 kg/ha, may not fully reflect the variability across individual orchards, production goals, or environmental variability. In 2023, 216 peach trees were established in Clanton, Alabama, to evaluate the effects of three nitrogen fertilization levels (0%, 50%, and 100% of guideline rates) and irrigation on early tree development and nutritional status. The experimental design follows a split-split plot structure, with irrigation as the main plot factor (2 levels: irrigated vs. non-irrigated), fertilization levels as the subplot factor (3 levels: 0%, 50%, 100%), and cultivars (3 cultivars: 'AugustPrince', 'FirePrince', and 'RubyPrince') as the sub-subplot factor. Results from 2023 and 2024 indicate that irrigation significantly enhanced tree height and trunk diameter. Trees receiving 50% and 100% nitrogen performed similarly in growth and CO₂ assimilation, both outperforming unfertilized controls. However, nitrogen deficiency was observed in all 0% treatments and some 50% fertilized, irrigated trees, particularly ‘AugustPrince’ and ‘FirePrince’. ‘RubyPrince’ exhibited the longest terminal shoot length and bud density, followed by ‘FirePrince’ and ‘AugustPrince’, a pattern that aligned with cultivar ripening times. While irrigation improved assimilation and growth, its effect on terminal shoot length was not significant. These findings suggest that moderate fertilization, when paired with appropriate irrigation may help support early vegetative growth. Nonetheless regular nutrient monitoring remains critical. Future work will focus on evaluating yield and fruit quality on these treatments.

Blueberry has a high cost of establishment, requiring the incorporation of soil amendments and the use of chemical fertilizer to obtain high fruit yield and quality. Reducing establishment and fertilizer costs in blueberry production without affecting yield and fruit quality is key for blueberry producers. In this project we evaluated the impact of reducing fertilization, using biochar as a soil amendment, and the effect of different pruning techniques on plant nutrient status, plant growth and development, and fruit production and quality. Despite the importance of these cultural practices, there is a lack of research that explores the impact of combining varying fertilization rates, soil amendments, and different pruning techniques in Georgia. To test these three factors an experimental plot was designed in a factorial arrangement with two soil amendments: 1) 33% v/v pine bark and 2) 9% v/v biochar; three fertilization rates: 1) Commercial fertilization (lb/acre): N 90, P 75, K 75; 2) half commercial fertilization N 35, P 35, K 35; and 3) potassium only: N0, P0, K 35, and two pruning treatments: 1) winter hand pruning summer hand - tipping and 2) summer hedge. Each treatment was randomly assigned three replications and four plants per replication. Our results indicated that the highest net income was obtained from the treatment in which the soil was amended with pine bark; plants were treated with half of the fertilizer rate and hedged after harvest. Blueberry plants that were hand-pruned had bigger and heavier berries. Plants that were hedged after the harvest had higher yields and it did not affect plant growth. In addition, reducing the fertilization rate to half did not affect the yield and fruit quality parameters of berries harvested. Furthermore, the treatment in which plants received only potassium fertilizer resulted in notable decreases in berry weight, firmness, and plant growth. The use of biochar as a soil amendment significantly enhanced TSS and anthocyanin content, but the concentration of K, Mg, and Mn in the berries was lower than those of plants in which the soil was amended with pine bark treatment.

Southern highbush blueberry (SHB) cultivars are susceptible to spring frost damage, which can significantly reduce both yield and fruit quality. To mitigate the impacts of frost, alternative production systems, such as high tunnels, have been explored for their potential to improve SHB production. This study evaluated the performance of three SHB cultivars (‘Meadowlark’, ‘Victoria’, and ‘Jewel’) under high tunnels (HTs) and open fields (OFs). Stomatal conductance (SC), stomatal density (SD), stomatal area (SA), fruit quality, and quantity were measured, and weather variables were recorded. Data were analyzed using Proc Glimmix and Tukey’s HSD test was applied for mean separation (p ≤ 0.05). SC varied significantly by cultivars (p < 0.001) and production systems (p < 0.001), with higher SC observed in OFs. ‘Meadowlark’ exhibited the highest SC followed by ‘Jewel’ and ‘Victoria’. SD and SA were significantly influenced by the production systems and leaf stage, with all three leaf stages in OFs showing the highest SD and SA compared to HTs. SD was greater in younger leaves and decreased with leaf age, whereas SA was higher in mature and older leaves. Cultivars also affected SD and SA, with ‘Meadowlark’ showing the highest SD and SA, followed by ‘Victoria’ and ‘Jewel’. The yield was higher in HTs across all cultivars, with ‘Victoria’ producing the highest yield followed by ‘Jewel’ and ‘Meadowlark’. Single berry weight was significantly affected by both cultivars and production systems (p = 0.0004), with ‘Meadowlark’ and ‘Victoria’ producing larger berries in HTs, while ‘Jewel’ had the smallest fruit in both systems. Brix levels were cultivar dependent (p = 0.0005), with ‘Meadowlark’ exhibiting the highest values. Firmness was influenced by cultivars (p < 0.001) and among three cultivars, ‘Meadowlark’ had the highest firmness, while ‘Jewel’ had the lowest. In conclusion, SHB cultivars in HTs likely optimized their water use efficiency by reducing SC, SD, and SA. ‘Victoria’ demonstrated superior yield performance, while Brix value and firmness were higher in ‘Meadowlark’, resulting in better fruit quality. Additionally, HTs enhance total yield, berry weight, Brix, and firmness in SHB cultivars. Overall, this comparison highlights system-specific effects on cultivar performance, emphasizing the practices for southern highbush blueberry production.

The global increase in ornamental crop production has driven horticultural researchers to better understand the efficiency and sustainability of production input. Soilless substrates serve a crucial role in supporting outdoor nursery-grown plants, where container substrates must maintain sufficient moisture supply to the rootzone and continuously sustain shoot water loss. Nursery producers regularly face a changing climate, where unprecedented droughts, prolonged and increased air temperatures, and subsequent mandated water application restrictions present challenges for profitable harvests and yields. To date, there are little to no means in predicting container nursery stock performance, especially when grown in substrates with different water supply capacities (i.e., water storage and hydraulic transfer properties). Models have been used to predict plant responses to water stresses in soil systems based on dynamics of hydraulic conductance in the soil-plant-atmospheric-continuum (SPAC); though, no SPAC models have been applied to horticultural plants grown in soilless substrates. To better prepare for climate-challenges in nursery production systems, new methods of understanding substrate capabilities to withstand harsh growing conditions are needed. The study herein uses predictive tools (i.e., SPAC models) derived from measured data, namely substrate and plant hydraulic characteristics, to understand how plants respond (i.e., physiological output; water loss) when grown in harsh growing conditions (e.g., drying substrate and atmosphere). Plants were grown in four differing bark particle diameters: (1) 6.3 mm. Substrate water potential were maintained between -50 and -100 hPa to produce plants at similar water availabilities. Substrate hydraulic conductivity decreased as particle size increased, highlighting different water transfer properties across substrates at similar water availabilities. Plants produced in finer textured substrates had greater root and shoot morphological development, including greater fine root growth and aerial biomass. No differences were detected in root and shoot hydraulic conductance. The SPAC models showed that plants grown in finer textured substrates were able to maintain physiological function longer under drying substrate or atmospheric conditions, while plants grown in substrates with lower water transfer properties sharply decreased physiological output (i.e., faster stomal closure). The hydraulic models applied herein can inform growers that producing plants in finer textured substrates, or substrates that have greater hydraulic conductivity, can enable plants to maintain physiological functions even in harsh growing conditions.