ASHS 2025 Conference

Plant growth and development depends on essential macronutrients such as nitrogen (N), phosphorus (P), and potassium (K), and deficiencies in these nutrients result in significant physiological and morphological changes. Leaf biochemical and biophysical properties influence light absorption and reflectance across various wavelengths, providing insights into canopy health. Advancements in high-throughput (HT) digital phenotyping technologies, including high-resolution scanning and multispectral imaging, have improved plant health assessment and monitoring. The TraitFinder, a digital phenotyping system developed by Phenospex, is equipped with two PlantEye-600 multispectral 3D laser scanners that generate three-dimensional plant models while capturing multispectral data. The system directs light in green (G), blue (B), red (R), and near-infrared (NIR) wavelengths onto the plant canopy and captures the reflected signals, which are then used to compute vegetation indices for plant health evaluation. This study utilized the TraitFinder system to determine reference values for vegetation indices associated with healthy plants and those deficient in N, P, and K. Four ornamental species—coleus (Solenostemon scutellarioides), marigold (Tagetes patula), petunia (Petunia × hybrida), and celosia (Celosia plumosa)—were evaluated over time. The experiment followed a randomized complete block design with eight replications and four nutrient treatments: a complete Hoagland’s solution and three modified versions, each lacking one macronutrient (N, P, or K). Morphological traits, such as biomass, showed reduced plant growth under nutrient-deficient conditions. Spectral data revealed common trends in nutrient-deficient plants, including decreased Green Leaf Index (GLI) and Normalized Difference Vegetation Index (NDVI) and increased Normalized Pigment Chlorophyll Ratio Index (NPCI) and Plant Senescence Reflectance Index (PSRI) compared to controls. In healthy plants, GLI ranged from 0.2 to 0.35, NDVI from 0.4 to 0.75, NPCI from 0.10 to 0.45, and PSRI from 0.07 to 0.25. However, species-specific responses to nutrient deficiencies were also observed. This study highlights the distinct morphological and physiological responses of ornamental species to macronutrient deficiencies and demonstrates the effectiveness of digital phenotyping using the TraitFinder system for tracking plant health over time. The findings emphasize the potential of HT digital phenotyping which could enhance ornamental crop management.

Easter lilies (Lilium longiflorum) cultivated in the greenhouse industry are often treated with plant growth regulators (PGRs) to control their height by reducing stem length. A greenhouse study was conducted to examine the effects of uniconazole “Sumagic” on the growth of a new cultivar of Easter lilies ‘White Spring’. Treatments consisted of five bulb sizes based on circumference (12/14, 14/16, 16/18, 18/20, 20/22 cm) and uniconazole rates of 0, 2.5, and 5.0 mg•liter-1 with eight replications. Data collection consisted of stem height measured weekly, days until anthesis, number of flowers, and phytotoxicity rating. The results of the study showed a relationship between the uniconazole treatments and plant height, control plants had a greater average height (57.8 cm) than the bulbs soaked in 2.5 and 5.0 mg•liter-1 uniconazole, (33.5 cm) and (23.8 cm), respectively. Plant heights were also influenced by bulb size as they increased in height with increase in bulb circumference. The average number of days until anthesis increased with smaller bulb circumference, as anthesis was delayed. Days until anthesis were also affected by the uniconazole treatments, the bulbs treated with 2.5 and 5.0 mg•liter-1 solutions took approximately 6 and 8 days longer, respectively. Phototoxicity effects displayed as chlorosis on leaf tips and margins occurred in both the 2.5 and 5.0 mg•liter-1 solutions with symptoms more prominent in larger bulb sizes.

Soil pH shapes rhizosphere microbial structure and diversity, influencing nutrient cycling, plant growth, and ecosystem health. However, the effects of pH on the microbiome in greenhouse-grown ornamental plants in peat-based soilless substrates are less well understood. This study examined the impact of substrate pH and plant species on rhizosphere bacterial communities to see how the interaction of these factors influenced microbial diversity. A two-factor experiment with substrate pH (4.5, 5.5, 6.2, and 7) and plant species (geranium, marigold, petunia, and tomato) was conducted in a greenhouse with six replicates per treatment (n=6) in a random complete block design. Substrate-only controls were included at each pH level to evaluate plant species influence on the bacterial community. The peat-based substrate pH was adjusted with dolomitic limestone. Plants were fertilized at each irrigation with 100 µg·g-1 N from 15-5-15-Ca-Mg fertilizer. After eight weeks of growth, the ornamental plants were fully flowering, and the tomato plants were beginning to bud. At that time, plant morphology and vegetative indices were evaluated by 3D image analysis, vegetive tissue and substrate leachate were evaluated for nutrient content, and rhizosphere samples were collected to evaluate bacterial composition and diversity by 16S amplicon sequencing. Plant species differentially modified the substrate pH from the starting levels. Geranium and marigold acidified the substrate, tomato tended to increase substrate pH, and petunia maintained pH close to the initial values. Shannon diversity indices indicated that bacterial diversity varied across the pH and plant species treatments. At pH 4.5, geranium, marigold, and tomato plants reduced the diversity relative to the no plant control. Geranium and tomato plants also reduced diversity at pH 5.5, while petunia plants at 5.5 exhibited the highest diversity across all plant species (p=0.0159). Beta diversity analysis identified pH as the dominant factor explaining 53.7% in Bray-Curtis dissimilarity and 68.5% in the weighted UniFrac distance metrics (both p

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.

Increasing the efficiency of irrigation practices is necessary to conserve water resources. However, extreme reductions in irrigation may lead to stunted growth. In this project, we aimed to evaluate if chitosan applied as a substrate amendment influenced plant growth, physiology, and marketable parameters of container-grown ornamental crops cultivated at different container capacities. The experiment was a full-factorial design with two factors: container capacity (100%, 70%, and 40%) and chitosan application timing (No application, Week 1, Week 3). The plants were kept in the greenhouse for six weeks and then in growth chambers set at 30°C or 40°C for two weeks to simulate post-production conditions. Plant growth and stomatal conductance were measured weekly and flower area after the sixth week. Significant differences were observed between the treatments. Plant growth was lowest at 70% and 40% CC when chitosan was applied at week 3. The stomatal conductance of plants under 70% and 40% CC was higher than 100% CC with no chitosan, but plants with chitosan at 40% CC had higher stomatal conductance. Flower coverage did not differ at the end of the crop cycle and in the first week at the two post-production temperatures (30°C and 40°C), but in the second week, the flower coverage decreased drastically in all the treatments, with the lowest values observed at 100% CC in both environmental temperatures. Deficit irrigation in petunia plants could be a strategy to produce marketable plants while reducing the volume of water. Chitosan applied in the first week of production seems to be the best application timing under deficit irrigation to see an amelioration effect from lowering container capacity.

Overwatered spring crops are subject to a range of biotic and abiotic disorders including hypoxia, nutrient deficiencies, and increased susceptibility to root rot diseases. Defining parameters associated with under- and overwatering would demonstrate how watering practices influence growth and abiotic disorders that develop during greenhouse production. Growth and nutrient content of petunia ‘Cascadias Indian Summer’ (IS) and ‘Headliner Strawberry Sky’ (SS; Expt. 1) and calibrachoa ‘Aloha Kona Midnight Blue’ (MB; Expt. 2) plants were grown under three different watering regimes of overwatered (rewatered when weight of sentinel pots dropped to 90 to 95 5% of container capacity, CC), optimally watered (60 5% of CC), and underwatered (35 to 45 5% of CC) and two different fertilizer sources of Jack’s Professional General Purpose and Jack’s Classic Petunia Feed. Across both plant species, the optimal watering regime generally yielded the largest plants based on width, fresh and dry weights. SPAD readings of youngest foliage were different based on fertilizer source. While IS petunia did not develop yellowing of youngest foliage in any treatment, SS petunia developed distinctive symptoms of interveinal chlorosis in youngest foliage of overwatered plants fertilized with general purpose fertilizer. However, tissue analysis of SS petunia revealed no difference in Fe between watering regimes or fertilizer formulations. Differences did occur across watering regimes in tissue P, K, Ca, Mg, S, and Mn and between fertilizer formulations in P, Mg, and S. Overwatering induced visual symptomology of chlorotic young foliage in SS petunia and MB calibrachoa, but not IS petunia, which suggests a genetic component to the disorder. Symptomology is effectively mitigated by using petunia feed. Tissue nutrient content is affected by overwatering, but Fe is not significantly different. Future work will explore a mechanism associated with substrate microbial activity that explains these results.

Sugarcane bagasse (SCB), a byproduct from the refinement of sugar, is an abundantly available material in tropical and semi-tropical regions. The use of SCB as a component in soilless substrates and other horticulture applications has gained attention due to its regional availability, use as a peat alternative in floriculture production, and as a phosphorus-rich material. Phosphorus (P) is an essential element for the growth of plants; however, P leaching losses from excessive fertilizer applications can pose environmental concerns. This study evaluated using SCB as a soilless substrate amendment in the production of Petunia ‘E3 Easy Wave Coral’, where two particle sizes of SCB (hammermilled at 4 mm and 6 mm) were blended with a peat moss/perlite (7:3 by vol.) floriculture media at rates of 15% and 30% by volume. Two fertilizer rates were investigated, one applying P at 100 mg L-1 and one applying P at a reduced rate of 30 mg L-1. Plant growth and vigor was assessed through measuring growth index (average of plant height and two widths) and chlorophyll content (SPAD). Leachate collected from containers following the “Pour-Through” method was assessed for pH and electrical conductivity (EC), with subsamples collected and analyzed for nutrient content. Plants appeared to grow larger in the control (peat moss/perlite media only) and 15% SCB amended soilless substrates compared to the 30% SCB substrates, regardless of SCB size or fertilizer rate. Substrates amended with SCB at 30% resulted in less vigorous growth than either the control or the 15% SCB amended substrates; however, the differences were less visible in the 30% SCB media when provided the higher P fertilizer rate. Given the important role of P in plant growth and the environmental concerns associated with fertilizer applications, evaluating P availability in sugarcane bagasse and its potential contribution to plant nutrition could provide a more sustainable alternative for soilless substrate systems in floriculture production.

In high latitudes (≥40°), commercial greenhouse growers utilize supplemental lighting (SL) and heating to offset low solar radiation, air average daily temperature (ADT), and root-zone temperature (RZT) during peak young-plant production. Growers have historically used high-pressure sodium (HPS) lamps to deliver SL but are transitioning to light-emitting diode (LED) fixtures, mostly because of their improved energy efficacy. However, many growers report changes in crop morphology and undesirable purple leaf pigmentation when cuttings of some species, especially petunia (Petunia ×hybrida), were grown under LEDs. The objectives of this study were to 1) quantify how light intensity during callusing, ADT, RZT, and SL sources influence the morphology, rooting, leaf pigmentation, and quality of petunia and to 2) develop strategies to mitigate the purpling of leaves. Shoot-tip cuttings of petunia SureShot ‘Dark Blue’ and ‘White’ were inserted into 72-cell trays and propagated inside a greenhouse at an air ADT of 21 or 23 °C and with an RZT of 21 or 25 °C. Cuttings were grown under SL delivered by HPS lamps or LED fixtures proving different light qualities (low blue or moderate blue) at a photosynthetic photon flux density of 60 or 120 µmol·m–2·s–1 for the first 6 d, then 120 µmol·m–2·s–1 for the remaining 16 d. Cuttings of both cultivars grown at an air ADT of 23 °C often had greater stem lengths and shoot dry masses than cuttings grown at 21 °C, as well as lower concentrations of anthocyanins. Cuttings of both cultivars grown with an RZT of 25 °C typically had longer stems than those grown with an RZT of 21 °C. Overall, cuttings of both cultivars propagated under LEDs were of greater quality (shorter stems, greater root dry mass) than those grown under HPS lamps. The color of cuttings grown under LEDs were more red and blue than those grown under HPS lamps, especially at low ADT and RZT. Additionally, the anthocyanin content of ‘Dark Blue’ cuttings grown under LEDs was greater than those grown under HPS lamps. Little differences were observed between cuttings grown under either LED fixture. These results indicate that growers using LEDs may have to adjust other environmental parameters, such as light intensity, ADT, and RZT, to produce cuttings of similar morphology and quality to those grown under HPS lamps.

Photo-selective shade nets substantially benefit ornamental plant production by mitigating excessive radiation, enhancing light diffusion, and promoting adequate ventilation. These nets establish favorable microclimates that optimize water utilization, thereby reducing plant water demand through physiological and environmental adjustments. Shade nets of different colors vary notably in their spectral distribution and light transmission characteristics, directly impacting plant morphology, physiology, and development. This study aimed to evaluate how different colored photo-selective shade nets influence physiological, morphological, and floral characteristics, as well as water usage, in Zinnia elegans ‘Cherry Queen’. We used four distinct shade net colors: blue, red, white, and black with 30% shade factor as treatments. The 107 cm x 61 cm shade structure was prepared using the PVC pipes with different colored shade nets wrapped around it. Seeds of zinnia were sown in a commercial substrate, Metro-Mix® 820, and kept on a misting bench. Following germination, the plugs were transplanted in a 3.6 L pot filled with the same commercial substrate and kept under four distinct color shade nets. Substrate moisture content was consistently maintained at 35% volumetric water content using an automated irrigation system using capacitance-based soil moisture sensor, ECH20 10HS from Meter Group. Black shade nets transmitted the least radiation across all wavelengths. Blue shade nets increased transmission in blue and green wavelengths while reducing red and far-red light transmission. Red shade nets enhanced red and far-red wavelength transmission, whereas white nets provided the highest overall radiation across all wavelengths. Morphologically, plants grown under red and white shade nets exhibited similar growth and floral characteristics to those under blue nets, and all showed improved growth compared to plants under black nets. Physiological responses, including photosynthetic assimilation rate, stomatal conductance, chlorophyll fluorescence (Fv/Fm), Soil Plant Analysis Development (SPAD), Normalized Difference Vegetation Index (NDVI), and anthocyanin content measured via leaf spectrometry remained similar across all treatments. Water use per plant was highest under white shade nets, significantly exceeding usage under black nets but comparable to blue and red nets. Growers may prefer red or white shade nets for optimal growth and water efficiency, blue for balanced spectral quality, or black for reduced radiation needs.

Maryland’s cut flower industry represents an expanding sector within the broader U.S. horticultural market, currently valued at $6.69 billion with Maryland alone contributing significantly ($139 million in 2018). Recent surveys conducted at the 2025 Bay Area Fruit School and University of Maryland Eastern Shore, Small Farm Conference-2024 provided critical insights into the demographic diversity, interests, and barriers faced by Maryland cut flower growers. Survey results indicated a diverse population, with participants spanning various ages, experience levels, and farming backgrounds. The largest demographic segment (25%) ranged between 35-44 years, suggesting an active, economically productive age group interested in cut flower production. Notably, the survey underscored a strong existing interest, with half of the respondents expressing a high level of enthusiasm toward cultivating cut flowers. Despite this enthusiasm, significant barriers impede growth and expansion. Key limitations identified included a lack of expertise and technical knowledge (41.7%), limited availability of relevant workshops and training (33.3%), and restricted market access (37.5%). Other reported challenges comprised high production costs (29.2%), pest and disease management issues (25%), limited labor availability (20.8%), and environmental factors such as weather variability and soil conditions. Dahlias emerged from these findings as a particularly promising crop, offering distinct advantages for Maryland farmers, especially those with constrained resources. Due to their delicate blooms and brief vase life, dahlia imports into the U.S. are minimal, primarily limited to pompon varieties. This creates a substantial market gap and an opportunity for local growers to supply diverse, premium-quality blooms tailored to consumer preferences. Consumers increasingly favor locally grown, sustainably produced flowers, especially when sourced directly from local farms, enhancing market potential for dahlias. To enhance dahlia production in Maryland, growers should consider collaborative research trials and evaluations of variety selection, sustainable cultural practices, and integrated pest management strategies under varying conditions, including open fields and protected cultivation such as high tunnels. Developing specialized extension materials, hands-on workshops, and practical demonstrations can also significantly address existing knowledge gaps. Such focused, region-specific guidance and facilitation of access to lucrative markets would empower Maryland's small-scale growers to capitalize fully on the growing demand for locally produced specialty flowers, significantly enhancing their productivity, profitability, and long-term sustainability.

Ranunculus are sensitive to high soil salinity and to high chloride concentrations. A trial was set up in fall 2024 at the Flower Fields in Carlsbad, CA to evaluate the yield and quality parameters of field-grown ranunculus under three irrigation water treatments and corresponding increasing levels of water salinity. The treatments were 1) Municipal water, currently used at the Flower Fields to grow ranunculus and other crops; 2) a 50:50 blend of municipal water and reclaimed municipal water; 3) 100% reclaimed water (called hereafter “recycled”). The objective of the study was to investigate if a blend of municipal and reclaimed water or 100% reclaimed water can be used in the future to grow ranunculus at the flower fields. The expected salinity levels in the water, measured as electrical conductivity before fertilizer injection were

Floriculture supply chains are undergoing a shift toward sustainability, driven by consumer demand and industry initiatives to reduce environmental impacts. While previous research has explored the carbon footprint of some ornamental horticultural products, domestic U.S. cut flower production and distribution remains largely understudied. Understanding the emissions associated with different supply chain models can guide sustainable practices in the domestic floriculture industry. This study examines the carbon emissions from the production and transportation of one representative cut flower species – snapdragon. Two primary distribution models were compared: point-to-point delivery where individual growers supply retailers directly and the hub-and-spoke system where wholesale hubs consolidate and distribute flowers. By evaluating data collected from 188 growers, 330 retailers, and six regional wholesale hubs, the research quantifies carbon emissions at each stage of the supply chain. The life cycle analysis uses openLCA software to standardize emissions data to an "emissions per stem" metric, aligning with horticulture footprinting standards. The results highlight the importance of optimizing supply chain logistics to reduce emissions. Furthermore, applying the social cost of carbon ($185 per metric ton of CO2) provides an economic perspective on the environmental impact of floral supply chains. As businesses move toward more climate-conscious operations, these insights can guide decisions that align with both financial and sustainability business goals.

Caladiums (Caladium x hortulanum) are popular ornamental plants prized for their vibrant foliage and unique patterns. The great majority of caladium tubers used by the U.S. and the world are produced in Florida. The tuber production process typically begins in March, with harvesting taking place between November and February. During this period, plants are exposed to high temperatures, high radiation, high relative humidity, heavy rainfall, and tropical storms, resulting in multiple stresses on the plants. Research in other crops has demonstrated the effectiveness of clay-based products in reducing leaf temperatures and protecting plants from environmental and/or biological stresses. This study aimed to assess the plant growth, quality, and tuber production of five caladium cultivars ('Tapestry', 'Lava Glow', 'Wonderland', 'Pink Panther', and 'Summer Pink') under different kaolin clay treatments. Field-grown plants were sprayed throughout the season with either kaolin, kaolin with red dye, or left untreated (control) to assess their response. An adjuvant was added to prevent excessive washout from rainfall. Data collected over two seasons included plant height, canopy coverage, and volume (per plot) extracted from multispectral images captured by a small uncrewed aerial system, leaf temperature using an infrared thermometer, chlorophyll content using a SPAD meter, and subjective ratings for plant color display, leaf health, and plant fullness using a scale from 1 to 5. At harvest, tuber production was evaluated through fresh weight, dry weight, and production index. Results showed that the growth curves for plant height, canopy coverage, and volume exhibited a bell-shaped curve, with an initial linear growth and a maximum peak in early to mid-September for most cultivars, except 'Summer Pink', which peaked later. Treatment differences were not statistically significant, with cultivar variations being the primary factor. However, kaolin and kaolin red treatments effectively reduced leaf temperatures during the 2023 production season, with kaolin red also receiving a higher rating for color display. Plants under kaolin treatments displayed lower chlorophyll content compared to untreated plants. Tuber production was unaffected by the treatments but showed differences among the cultivars, with 'Tapestry' producing the highest tuber dry weight. The production index, which accounts for tuber grading, number, and relative economic values, revealed that 'Summer Pink' had the highest value compared to 'Tapestry'. This study provides valuable insights into the growth behavior of caladium cultivars and the potential benefits of using kaolin treatments as a crop protection strategy.

Peatmoss, a commonly used substrate component, is facing numerous challenges to remain a sustainable option for horticultural production. Due to mounting factors such as weather-limited harvesting, increasing transport costs, waning public acceptance, and now potential international tariffs, many are searching for alternative materials to replace some of the peatmoss in their operations. Biochar is one such alternative that may present numerous benefits as a peat alternative in container production. Biochar is the product of the pyrolysis of biomass (commonly agricultural residues) in an oxygen limited environment, resulting in a product that has increased porosity, increased water and nutrient retention, and can be produced regionally from a number of sources. Incorporating biochar into container production can reduce peat use and improve nutrient retention. However holistically blending can prove costly and alter the substrate physical properties, requiring major changes to production practices, an obstacle that can be considered a barrier. The use of stratification has been shown to successfully reduce peat use while maintaining highly productive growing conditions. With stratification, growers can incorporate alternative materials strategically in the container while limiting the associated costs. Therefore, this study was designed to evaluate the effect of sugarcane bagasse biochar on nutrient retention in both stratified and non-stratified peat-based container systems. Nine peat-based substrate treatments were utilized in this study, with either the entire container filled with peat-based substrate or stratified above a pine bark or hammermilled wood fiber. Within each substrate, sugarcane bagasse biochar was amended at 0 (control) or 10% of the container volume, by either blending throughout the container or blending at 20% upper strata only (equivalent to 10% by vol. overall). Petunia plugs were planted into 3.8 L containers filled with each of these different substrate treatments. The plants were placed on two different fertilizer regimes, with plants receiving either 100 ppm or 300 ppm fertilizer once a week. Leachate was collected biweekly to assess the impact on nutrient retention. Plant growth and nutrition were assessed. The incorporation of biochar has not significantly impacted plant growth; however, it has improved nutrient retention. Biochar improved nutrient retention in the plants stratified with wood fiber in both the high and low fertilizer regimes, while improving nutrient retention in stratified bark in the high fertilizer regime. The results indicate that strategic inclusion of biochar may reduce fertilizer application frequency.

Our objective was to evaluate the efficacy of benzyladenine or ethephon foliar spray applications to control growth and improve branching of ‘Dragon Wing® Red’ begonia (Begonia interspecific). On 10 Sep 2024, a 288-cell plug tray of ‘Dragon Wing® Red’ begonia was received from a commercial propagator. Plugs were transplanted into 15.2-cm-diameter containers filled with a commercially available soilless peat-based substrate. Plants were grown in a glass-glazed greenhouse under supplemental and day-extension lighting provided by 780-W light-emitting diode lamps from 0600 to 2200 HR (16-h photoperiod) with an air temperature set point of 20 °C. At 7 d after transplant, 10 single-plant replicates were treated with a solution containing benzyladenine or ethephon and a surfactant. Plants received a foliar spray (vol. 0.2 L·m–2) containing deionized water (0 mg·L–1; untreated) or 10, 30, 50, 70, or 90 mg·L–1 benzyladenine or 125, 250, 500, 750, 1,000, or 2,000 mg·L–1 ethephon. Benzyladenine and ethephon foliar spray applications influenced begonia growth and development differently. Benzyladenine concentrations increasing from 10 to 90 mg·L–1 suppressed growth index, an integrated measurement of height and diameter, by 1% to 3%, respectively, compared to untreated plants. Branch number increased by 32% to 64% (3 to 5 branches) as concentrations increased from 30 to 90 mg·L–1 benzyladenine compared to untreated plants. Shoot dry weight (SDW) decreased as benzyladenine concentrations increased, but time to flower (TTF) was unaffected. Ethephon concentrations increasing from 125 to 2,000 mg·L–1 influenced plant height, plant diameter, growth index, branch number, SDW, and TTF. Growth index was suppressed as ethephon concentrations increased from 125 to 2,000 mg·L–1, resulting in plants that were 11% to 30% smaller than untreated plants. Compared to untreated plants, ethephon concentrations increasing from 125 to 1,000 mg·L–1 improve branching with 1 to 2 more branches developed per plant. Ethephon concentrations of 125 to 2,000 mg·L–1 limited SDW by 23% to 49% compared to untreated plants. Time to flower was delayed by 3 to 10 d as concentrations increased from 125 to 2,000 mg·L–1 ethephon. Begonia plants sprayed with ≥750 mg·L–1 ethephon developed phytotoxicity and had reduced ornamental quality. Our results indicate that growers can attain growth control and enhance branching with foliar spray applications of 30 to 90 mg·L–1 benzyladenine or 125 to 500 mg·L–1 ethephon, but these should be used as an initial range for trials during greenhouse production.

Ethephon substrate drenches have been shown to effectively control growth of annual bedding plants and herbaceous perennials. However, research has shown the efficacy of ethephon substrate drenches is impacted by the time of application. Therefore, the objective of our research was to evaluate how ethephon substrate drenches impact growth when applied at varying times post-transplant. Young plants of lobed tickseed (Coreopsis ×hybrida Big BangTM ‘Mercury Rising’) and coleus [Coleus scutellarioides (L.) Benth. ‘Main StreetTM Bourbon Street’] were transplanted into 12.7-cm containers filled with a soilless peat-based substrate. At 3, 7, 10, 14, 17, or 21 d after transplant, 8 single-plant replicates received a single substrate drench of 90 mL aliquots of a solution containing 0, 25, 50, 100, or 200 mg·L–1 ethephon. Plants were grown in a glass-glazed greenhouse for 5 to 7 weeks after initial drench application before growth and morphological data including plant height, plant diameter, shoot dry weight (SDW), and root dry weight (RDW) were determined. In general, increasing concentrations of ethephon influenced plant height, plant diameter, SDW, and RDW of coleus and lobed tickseed. In Expt. 1, plant size (height and diameter) and biomass accumulation (SDW and RDW) of coleus was significantly influenced by increasing concentrations of ethephon, with the effects diminishing as application time was delayed. For example, as concentrations increased from 0 to 200 mg·L–1 ethephon, coleus treated at 3 days after transplant (DAT) were 33% (5.3 cm) shorter, while those treated at 17 DAT were 21% (3.6 cm) shorter. Shoot dry weight of coleus drenched with 200 mg·L–1 ethephon at 3 or 21 DAT were 50% (2.0 g) and 23% (1.0 g) lower, respectively, compared to untreated plants. Compared to untreated plants, RDW of plants drenched with 200 mg·L–1 ethephon 3 or 14 DAT was 65% (2.8 g) and 50% (2.6 g) smaller, respectively. In Expt. 2, plant height was unaffected by increasing concentrations of ethephon, but plant diameter and biomass accumulation of lobed tickseed was significantly affected. For example, as concentrations of ethephon increased from 0 to 200 mg·L–1, lobed tickseed treated 3 and 21 DAT were 8% (2.4 cm) and 9% (2.8 cm) narrower, respectively, compared to untreated plants. Overall, the magnitude of control diminished as application time increased and negative phytotoxic effects were seen in early applications (≤7 d). Therefore, we suggest applying ethephon substrate drenches 7 to 14 d after transplanting.

Calcium phosphate [Ca₃(PO₄)₂] is an nonlabile form of phosphorus (P) commonly found in substrates with a basic pH and it is not available for plant uptake. Phosphate solubilizing bacteria (PSB) are plant-associated microorganisms that can solubilize calcium phosphate by secreting organic acids. PSB inoculation alleviates P deficiency symptoms including leaf purpling, and PSB inoculum can be amended with substances that may improve PSB performance (i.e. glucose). Our goal was to evaluate the efficacy of PSB isolated from the rhizosphere of greenhouse ornamentals (Pantoea trifolii C2B11, Pantoea formicae C8D10, Pantoea sp. C2G6 and Enterobacter soli C4A1) in substrate with pH 6.0 or 6.5, and with an inoculum amended with glucose (10 g·L-1), Luria Bertani (LB) broth (111 mL·L-1), or humic and fulvic acids (20 g·L-1). An experiment was conducted using French marigold 'Durango Yellow' (Tagetes patula) fertilized once per week with 200 mg·L-1 N from a 15N-0P-12.5K-2.9Ca-1.2Mg fertilizer. P was supplemented to the fertilizer solution as Ca3(PO4)2 at 10 mg·L-1 P. Bacillus velezensis was included as a positive control. Digital biomass, Normalized Pigment Chlorophyll Ratio Index (NPCI), Plant Senescence Reflectance Index (PSRI) and canopy hue (color) were measured with the TraitFinder, a digital phenotyping workstation. NPCI and PSRI values from healthy foliage are low but increase under stress. At pH 6.0, all marigolds receiving PSB had increased growth regardless of the inoculum amendments. PSB amended with glucose resulted in marigolds with a lower NPCI than non-inoculated plants. Additionally, PSB-treated marigolds had a higher proportion of green canopy, and a lower proportion of red canopy compared to non-inoculated marigolds when the inoculum was amended with glucose or not amended. At pH 6.5, all PSB resulted in increased marigold growth regardless of inoculum amendments. PSB treated marigolds were healthier than non-inoculated plants, as indicated by their lower NPCI and PSRI values, regardless of the inoculum amendments. Accordingly, PSB treated marigolds had a higher proportion of green canopy and a lower proportion of red canopy compared to non-inoculated marigolds. Bacterial effects were more consistent when inoculum was supplemented with LB. A greater benefit was observed in plants grown at pH 6.5. Microbiome analysis of the rhizosphere showed that inoculation with C2B11, C2G6, and C8D10 increased the relative abundance of the genus Pantoea, and C4A1 enriched the genus Enterobacter. Careful determination of optimal inoculum supplements is key to developing efficient inoculants that promote growth in greenhouse ornamentals.

Supplying adequate iron (Fe) to greenhouse crops is challenging, particularly for iron-sensitive plants grown in soilless substrates under alkaline conditions. High pH levels reduce Fe bioavailability by promoting the formation of insoluble iron hydroxide (Fe(OH)₃), which limits plant uptake. Plant growth-promoting bacteria (PGPB) enhance plant growth and stress tolerance through diverse mechanisms, including siderophore production. Siderophores are small molecules that have a high affinity for metal ions like ferric iron (Fe³⁺). Once the siderophore chelates iron, the complex is soluble, and plant roots can readily absorb it. This study identified siderophore producing bacteria (SPB) capable of enhancing plant growth under Fe-limiting conditions. A rhizosphere bacterial collection from greenhouse plants was screened for siderophore production using the chrome azurol S (CAS) assay. Genomic analysis of 12 isolates identified in the CAS assay revealed diverse siderophore-related genes and other plant growth-promoting traits. Five of the isolates (C2G2, C5A12, C6E3, C8G7, and C10A8) were identified as strong candidates based on their siderophore-related genes and Fe uptake pathways. A ferrozine-based assay confirmed Fe solubilization in a modified Hoagland’s solution containing goethite (Fe³⁺O(OH)) as an insoluble Fe source, with bacterial treatments yielding 0.57 mg Fe L⁻¹ versus 0 mg Fe L⁻¹ in controls (no bacteria). Subsequent in planta experiments evaluated the impact of SPB on French marigold ‘Durango Yellow’ (Tagetes patula) growth in hydroponic systems under Fe-limiting conditions. French marigold proved to be a good model plant for this screening system. Digital phenotyping showed that plants inoculated with isolates C5A12, C8G7, or C10A8 had 53.0%, 45.7%, or 50.3% more green leaf tissue, respectively, compared to untreated control plants. Additionally, treated plants had increased root biomass. These findings demonstrate the potential of SPB to enhance Fe availability and plant growth under iron-limiting conditions and offer a novel strategy for improving greenhouse crop production. The incorporation of SPB into greenhouse practices may benefit Fe-sensitive crops or systems where pH fluctuations reduce Fe availability, ultimately improving crop quality and sustainability.

Increased interest in peat-alternative substrates has contributed to the development of both regional and global wood substrates. Utilizing different manufacturing equipment to produce wood fiber components allows producers to modify wood fibers/inputs through chipping, milling, heat, pressure, or various combinations, to alter physical properties and yield suitable material for horticulture use. Commercial substrates available for plant production include peat-reduced formulas with various percentages (by volume) of wood fiber. Current lime amendment suggestions to bring substrates into the optimal pH range for plant growth are based on peat as the main component. Wood fiber has variable initial pH across manufactured type and reacts differently to lime amendments compared to peat. To aid in the understanding of lime amendments to wood fiber substrate blends, this study was designed to measure the pre-plant pH response over time of substrates influenced by wood component type, peat inclusion percentage, and dolomitic lime amendment rate. Three types of manufactured wood substrates (hammermilled, screw-extruded, and disc refined) were individually blended with Sphagnum peat at 20% increments (20, 40, 60, 80, and 100%). Each substrate was amended with 0, 4, 8, or 12 lbs/yd3 dolomitic lime and incubated in plastic bags to measure pH change at 0, 1, 3, 5, 7, 14, 21, and 28 days after blending. Resulting pH values indicate dolomitic lime amendment rates will need to be adjusted based on peat:wood volume ratios. Wood fiber exhibited a higher initial pH than Sphagnum peat and within blends, as wood fiber rate increased, pH increased across all lime rates. Dolomitic lime amendments should be closely monitored at 40% volume or more wood fiber. Moderate pH differences were measured between manufactured wood fiber type within the same peat:wood volume ratio and lime rate, emphasizing interchangeability of wood component type.

Frass is the left-over substrate produced from mass rearing insects as food and feed. Black soldier fly (Hermetia illucens) larvae frass has become a popular option for vegetable production as a potential fertilizer and peat replacement. Controlled environment propagation of ornamental crops requires large amounts of peat, therefore researching alternative substrates has a rising interest for growers. Pansies (Viola x wittrockiana), Marigold ‘Inca II’(Tagetes erecta), and Marigold ‘Safari’(Tagetes patula) were grown in growth chambers to evaluate the incorporation of frass into peat based substrates for ornamental production: 3 treatments from previous studies (BSF 10, 20, and 30%), 1 treatment included to assess the impact of leaching on frass (BSF 40-), and a 100% peat control (CP 100%). Pansies grown in the BSF treatments of were statistically comparable to the control in all parameters except, root weight. Pansy root weight was significantly higher in the treated BSF 40- treatment. BSF 40% produced the lowest values in all crops and parameters, except for Marigold ‘Inca’ root weight, where only BSF 40- was significantly higher. BSF 40- was significantly greater or equal to the control in all crops and parameters, except for Marigold ‘Safari’ plant size and root weight. Chlorophyll concentrations were statistically comparable across all treatment and control in all crops. Past research and this study generally indicate that at large concentrations, like 40%, frass can have negative outcomes for crop production in peat based substrates. However, due to the success of our leached treatment, BSF 40-, it seems frass can be utilized at larger concentrations, but additional alterations may be required before mixing into growing medias and substrates. Additionally, certain crops appear to have more neutral and positive reactions to frass incorporation. Engaging efforts to target ideal crops will improve the application and practicality of this research.

Phosphorus (P) is an essential macronutrient required for plant growth. In fertilizers used for soilless substrates, P is in the form of phosphate and is readily leached from containers leading to environmental contamination. The FeSO4 bridge method has been proposed to reduce P losses by forming insoluble iron-phosphate complexes that retain P within the substrate, but reduced bioavailability may limit plant growth. The aim of this research was to evaluate the FeSO4 bridge method in combination with inoculation of the substrate with phosphate-solubilizing bacteria (PSB) and siderophore-producing bacteria (SPB) to gradually release P for plant uptake. An experiment was conducted to evaluate the growth of marigolds ‘Durango Yellow’ (Tagetes patula) using a substrate composed of 80% peat and 20% perlite by volume, with substrate either amended or not amended with 3.0 kg·m-3 FeSO4·7H2O. After transplanting, plants received 100 mg·L-1 N from 15N-2.2P-12.5K-2.9Ca-1.2Mg Jack’s Professional water-soluble fertilizer as the P source for two weeks to promote the formation of iron-phosphate complexes. Additionally, two bacterial application strategies were evaluated: one starting from transplanting and another applied when P deficiency symptoms appear, with three weekly inoculations each. The bacterial treatments included: a control without bacterial inoculation; three PSB strains, Bacillus megaterium (C3F10), Pantoea rwandensis (C3A8), and Pseudomonas sp. (C6E7); one SPB strain Pseudomonas soli (C10A8); and a commercial inoculum of Bacillus velezensis (from the biostimulant LalRise Vita, Lallemand, Inc). Plants were grown under controlled greenhouse conditions, with weekly measurements of spectral variables and morphological parameters using the TraitFinder digital phenotyping system. Leachate was collected using the pour-through method and analyzed for P concentrations using ion chromatography. The results confirmed that the FeSO4 bridge method formed iron-phosphate complexes, reducing P leaching when amending the substrate with 3.0 kg·m-3 FeSO4·7H2O compared to non-amended substrate. Visual differences in plant growth were observed among treatments, with better outcomes when bacterial inoculation started at transplanting. In contrast, plants that received bacterial treatment after symptoms appeared could not recover, showing significantly reduced visual quality. Among the bacterial treatments, Pseudomonas soli (C10A8) promoted the highest biomass accumulation and spectral variables such as hue and green leaf index (GLI) indicated improved visual quality compared to the control (no bacteria) and other bacterial strains. These findings demonstrated that amending soilless substrates with FeSO4, combined with bacteria like Pseudomonas soli (C10A8), enhances P retention while promoting plant growth. This method offers growers a practical approach to reducing environmental impact while maintaining crop quality.