Multiple Foliar Applications of Ethephon for Growth Control of Lantana Camara - Lark Wuetcher Ethephon Substrate Drenches Control Growth of Containerized Annual Bedding Plants and Herbaceous Perennials - William Rich Microbial Communities in the Vertical Profile of a Container Substrate - Silvia Valles Ramirez Moisture Content Effects Microbial Activity in Substrates Derived from Five Different Hammermilled Wood Species Over the Course of Greenhouse Petunia Production - Amanda Mizell Stratification significantly reduces the phytotoxic effects of fresh hardwood - Andre Truter The Use of Machine Learning to Develop Refined Foliar Tissue Analysis Standards and Diagnostic Tools for for Petunia - Patrick Veazie Increasing the Nighttime Lighting Duration Can Hasten Flowering of Long-day Plants -Qingwu Meng Extended Storage of Cut Flowers Using Sub-zero Temperature - John Dole
Lantana (Lantana camara) is a popular annual bedding plant among consumers because it is heat tolerant and attracts pollinators with its vibrant and often multi-colored flowers. Greenhouse growers commonly apply plant growth regulators (PGRs) to control lantana growth and produce a compact, well-branched, and flower. Introduction of new lantana cultivars instigates review of previously known PGR recommendations. As such, the objective of this study was to evaluate the effectiveness of multiple foliar spray applications of ethephon [(2-chloroethyl) phosphonic acid] to control growth and stimulate branching of lantana ‘Bandana Red’. Unrooted cuttings of lantana were received from a commercial propagator and stuck into 105-cell plug trays (30-mL individual cell) filled with a propagation mix. Cuttings were propagated for 35 d under 23 °C air temperature, 24 °C root-zone heating, and a daily light integral of 12 mol·m–2·s–1. Rooted liners were transplanted into individual containers (11.4-cm; 600 mL) filled with a commercial peat-based substrate. Beginning 7 d after transplant, eight single-plant replicants received 1 to 3 foliar spray applications on a weekly basis containing 0 (control; deionized water), 250, 500 or 750 mg·L–1 ethephon. Plants were grown in a glass-glazed greenhouse at 20 °C under ambient daylight supplemented with a photosynthetic photon flux density of ≈125 µmol·m–2·s–1 delivered from LED arrays from 0600 to 2200 HR (16-h photoperiod) to achieve a daily light integral of 12 mol·m–2·d–1. At 42 d after transplant, plants were destructively harvested, and data collected. In general, multiple foliar spray applications with increasing ethephon concentrations affected lantana plant height, diameter, branch number, and shoot dry weight to different magnitudes. For example, lantana plant height was suppressed by 21% to 39% (12.7 to 9.7 cm) from 250 to 750 mg·L–1 ethephon, respectively, compared to untreated plants and were more compact as applications increased. Plant diameter decreased by 13% to 19% (25.5 to 23.7cm) compared to untreated plants as concentration increased from 250 to 750 mg·L–1, respectively, and as spray applications increased. A similar trend was observed for branch number and shoot dry weight. Overall, multiple foliar spray applications of 250 to 750 mg·L–1 ethephon can control the growth of lantana ‘Bandana Red’; however, growers will need to conduct in-house trials to evaluate the level of control desired. Further studies investigating the effects of multiple foliar spray applications with increasing concentrations of ethephon on additional lantana cultivars are warranted.
Containerized annual bedding plants and herbaceous perennials account for 57% of the 2020 U.S. floriculture market with a reported combined wholesale value of $3.2 billion. To produce high-quality, compact containerized ornamental plants, foliar spray applications and substrate drenches of plant growth regulators (PGRs) are often utilized. Ethephon [(2-chloroethyl) phosphonic acid] is a common PGR used to control growth, stimulate branching, and manipulate flowering, but is only labelled for foliar applications. Therefore, our objective was to evaluate the response of 35 floriculture species drenched with increasing concentrations of ethephon. Annual bedding plants and herbaceous perennials were received as unrooted cuttings and propagated at 23°C under 10 mol·m–2·s–1 for 21 or 28 d, respectively. Plants were transplanted into containers filled with a soilless substrate and grown in a glass-glazed greenhouse at 20°C under 14 mol·m–2·d–1. At 10 d after transplant, eight single-plant replicates received a substrate drench of 296-mL aliquots of solution containing 0 (control; deionized water), 25, 50, 75, 100, or 200 mg·L–1 ethephon for annuals or 0, 125, 250, 500, 750, or 1,000 mg·L–1 ethephon for herbaceous perennials. Plant growth metrics including height, diameter, shoot and root dry weight were determined 6 weeks after transplant. Time to flower was determined for select species by recording the date of anthesis for each plant. In general, plant height of annual bedding plants and herbaceous perennials were suppressed and shoot and root dry weight reduced as concentrations of ethephon increased. For example, petunia (Petunia × hybrida ‘Flame Red’) drenched with 200 mg·L–1 was ≈40% (5.8 cm) shorter than untreated plants. Similarly, in dahlia (Dahlia × hybrida ‘Dark Red’) height and diameter were decreased by 50% (15.4 cm) and 30% (12.4 cm), respectively as concentrations increased from 0 to 200 mg·L–1. In digiplexis (Digiplexis × hybrida), substrate drenches increasing from 0 to 1,000 mg·L–1 ethephon reduced shoot dry mass by ≈55% (17.1 g). Root dry weight of catmint (Nepeta faassenii) was reduced by 35% (1.54 g) as concentrations increased from 0 to 1,000 mg·L–1. Time to flower was unaffected at all concentrations of the species selected. These growth and development trends were reflected in most of the species evaluated. As such, this research demonstrates that ethephon, if labelled for substrate drenches, provides adequate growth control of floriculture crops.
A moisture gradient exists in containers filled with soilless substrates where the substrate is wetter at the bottom of the container and becomes drier towards the top of the container. This moisture gradient affects other substrate chemical properties and therefore may affect biological properties including the microbial communities present. Microbial communities in soilless substrates have only recently been studied and little is known about their uniformity throughout the container. This research aimed to evaluate how the bacterial and fungal portions of the microbial community may change along the vertical profile of a container substrate. A substrate was mixed that consisted of manure compost, peat moss, and perlite (20:65:15 v/v) and planted with a single sunflower seedling. After 0, 3, and 6 weeks in a greenhouse environment, samples of soilless substrate from the top, middle, and bottom of the container (approx. 4.3 cm depth for each layer) were collected for DNA extraction. Bacterial and fungal communities were characterized by sequencing PCR amplified 16s rRNA genes and ITS regions, respectively. We found that the phyla Pseudomonadota, Bacteriodota, and Ascomycota were present throughout the container profile in all three layers. However, bacterial genera Paucibacter, Pseudomonas, and Iodophanus, and fungal genera Cercophora and Mortierella differed in abundance within each layer. Pseudomonas tolerant to negative abiotic factors were greater in the bottom layer after 6 weeks. Likewise, Coprinellus , responsible for lignin and cellulose degradation, was also present only in the bottom layer. The diversity of bacterial communities differed between layers, with the greatest in the middle and the lowest in the top layer. The percentages of all bacterial amplicon sequence variants (ASVs) that were shared among the three layers at 3 and 6 weeks were only 16% and 28%, respectively. The diversity of fungal communities was less affected by layer and time, but the percentages of shared fungal ASVs among layers were still only 27% and 28% at 3 and 6 weeks, respectively. In consequence, it is necessary to consider sampling technique and location when collecting a DNA sample from a container substrate.
Recently, the limited availability of Sphagnum peat moss due to poor weather conditions impacting harvests, and additional scrutiny from media and public outlooks has brought up serious questions about the long-term security of peat use in the horticulture industry. The search for alternative amendments began decades ago, with several products being evaluated over the years. Many have been found suitable for niche production settings, with few seeming to fit the industry somewhat ubiquitously. Of these, wood fiber is seemingly the most promising as it is a renewable resource that is available globally. Wood fiber amendments have been trialed extensively with industry emerging and scaling internationally. Wood can be processed to support many different applications in horticulture, giving it more robust qualities than other top components. There are some disadvantages to wood usage, namely, nitrogen immobilization. Wood contains large amounts of easily degradable carbon. Therefore, microorganisms will consume this carbon for energy by utilizing plant available nitrogen causing plant nutrient deficiencies. Microbial community activity is heavily influenced by moisture. Considering this, a study was developed to observe how the microbial activity of different hammermilled wood tree species may be influenced by moisture content in a greenhouse crop production cycle. Five tree species (Abies concolor, Calocedrus decurrens, Pinus lambertiana, Pinus ponderosa, and Pseudotsuga menziesii) were harvested in California and hammermilled. The wood particles were blended with a commercial peat-based substrate at 30% (by vol.). Supertunia ‘Honey’ plugs were planted in each of the substrate blends and grown on a greenhouse bench for 75 days. The crops were held at 25% and 35% volumetric water content using cantilever-style lysimeters and fertigated with water-soluble fertilizer, weekly. Crop growth and performance was assessed throughout production. Substrate CO2 was assessed pre- and post- production to assess microbial activity. The results will help assess the potential of utilizing differing tree species for wood fiber, and understand any adjustments that will be necessary to production practices.
With a global increased demand for growing substrates and specifically wood alternative substrates, methods are being tested to better understand wood as a product and how to incorporate wood into growing medium substrates. This study investigated the use of fresh whole-tree loblolly pine and whole-tree hardwood in horticultural greenhouse settings, focusing on how varying wood blend compositions and levels of stratification affect plant growth. Analysis revealed that increasing hardwood percentage in blends led to decreased plant growth, while stratification reduced differences among blends. Notably, at lower stratification levels, plant growth resembled that of the control treatment. Statistical tests confirmed these trends, highlighting the significant impact of wood blend composition on plant dry weight. Findings suggest that while hardwood incorporation decreases growth, stratification can mitigate differences among blends, allowing for the incorporation of untreated wood material. These results offer insights for optimizing wood blend usage in greenhouse cultivation, providing sustainable solutions for horticultural practices. Key Words: Hardwood, Stratification, Phytotoxicity, Wood Blends, Plant Growth.
Foliar tissue analysis is utilized to diagnose a crop's nutrient status. For most floriculture crops a survey approach of a small population of plants (n= <25) of healthy appearing plants are used to establish sufficient nutrient standards. While this historical approach offers a baseline for the wide variety of floriculture crops there is a need for scientifically based ranges similar to those available in agronomic crops. For fast-maturing crops, utilizing foliar tissue analysis and correctly interpreting the results is critical in making fertility adjustments when problems arise. Foliar tissue analysis results of petunia (Petunia hybrida) were compiled from a variety of diagnostic and research institutions to account for variations of growing environments and classified into five ranges (deficient, low, sufficient, high, and excessive). To aid in foliar tissue analysis interpretation machine learning models were evaluated for accurate percent correct classification (PCC) into the sample's respective nutrient classification. Four separate machine learning algorithms were performed to analyze the data set including sequential minimal optimization (SMO) of support vector machines (SVMs) and multilayer perceptron (MLP) artificial neural network (ANN), and two decision tree models J48 and Random Forest (RF). Machine learning algorithms were compared to identify significant model nutrients based on a complete foliar tissue analysis report of 11 elements for the observations. The performance of both machine learning algorithms SMO and MLP were determined using PCC and during the cross-validation. By evaluating the foliar tissue concentration dataset of multiple species by 10-fold and 66% split cross-validations, the incorporation of five elements of ranked based on Shannon Entropy (Information Gain) was able to correctly classify tissue concentrations into one of five foliar nutrient classifications greater than traditional statistics. This information provides additional insight as to how examining nutrient relationships can assist in identifying fertility problems and classifying nutrient ranges.
Low-intensity (≈ 2 μmol·m−2·s−1) photoperiodic lighting is often delivered at night to promote flowering of long-day greenhouse ornamentals when natural days are short. Adding sufficient far-red (FR) light to red (R) light is necessary for the most rapid flowering in some crops, including snapdragon (Antirrhinum majus) and petunia (Petunia × hybrida). Specialty light-emitting diodes (LEDs) that include R FR light are effective at floral promotion but cost-prohibitive, whereas common warm-white (WW) LEDs lack sufficient FR light and can delay flowering. Because the duration to saturate flowering is longer than currently used (e.g., 4–8 hours) for some long-day plants, we conducted a replicated greenhouse experiment to determine how the WW or R FR LED lighting duration influenced flowering. We grew snapdragon ‘Liberty Classic Yellow’, petunia ‘Easy Wave Burgundy Star’, and petunia ‘Wave Purple Improved’ under truncated 8-hour natural short days with or without WW or R FR (1:1) LEDs operating for 0, 4, 8, 12, or 16 hours in the middle of each night throughout the experiment. Snapdragon flowered 13–16 days earlier under R FR LEDs than under WW LEDs regardless of the lighting duration. Increasing the lighting duration from 0 to 16 hours decreased flowering time by up to 16 days and decreased plant height and leaf number at flowering under R FR LEDs, but not under WW LEDs. For petunia ‘Easy Wave Burgundy Star’, although WW LEDs delayed flowering by 6–13 days but promoted lateral branching compared to R FR LEDs, the gap in flowering time narrowed as the lighting duration increased from 4 to 16 hours. Increasing the lighting duration improved the efficacy of WW LEDs, but not R FR LEDs. Flowering of petunia ‘Wave Purple Improved’ was unaffected as the lighting duration increased from 4 to 16 hours regardless of the lamp type and was delayed by 6–10 days under WW LEDs than under R FR LEDs. For both petunia cultivars, flowering time was similar under 16-hour WW LEDs and 4-hour R FR LEDs. In conclusion, increasing the nighttime lighting duration increased the efficacy of WW LEDs at promoting flowering of petunia and increased the efficacy of R FR LED lamps at promoting flowering of snapdragon. Delivering WW LEDs all night long can minimize flowering delay in petunia compared to R FR LEDs. In contrast, sufficient FR light was indispensable to promote flowering of snapdragon, for which WW LEDs were ineffective.
The cut flower industry needs postharvest techniques that allow for extended storage of fresh cut flowers to meet consumer demands. We evaluated the use of sub-zero storage temperature (-0.6 °C) to maintain viable flowers with improved or comparable vase life to flowers stored at the industry standard (4 °C) without sacrificing aesthetic appeal. The vase life of 17 commercially important cut flower species: alstroemeria, anemone, campanula, carnation, chrysanthemum, delphinium, freesia, gerbera, gypsophila, larkspur, lily, lisianthus, ranunculus, rose, stock, sunflower, and tuberose, when stored dry at -0.6 °C for durations of 4, 8, and 12 weeks was comparable to or longer than when stored at 4 °C. Tuberose stems were not viable after holding for any storage duration or temperature. Stems of carnation benefited from an 8-hour pre-storage pulse with a hydrating solution and maintained a similar vase life to non-stored control stems when stored for 4 weeks at -0.6 °C. Conversely, rose stems only maintained similar vase life to non-stored control stems when held at 4 °C for all pre-storage pulsing solutions (water, hydration or holding solution). Vase life of lily and chrysanthemum declined for all pre-storage pulsing solutions and stems only remained viable after 8 weeks storage when held at -0.6 °C. Additionally, stored chrysanthemum and lily stems had a longer vase life when stored at -0.6 °C than when held at 4 °C after 4- and 8-weeks storage, respectively, for all pre-storage pulsing solutions. Experiment 3 further evaluated carnation, lily, and rose stems with and without a pre-storage acclimation period at 4 °C for either 24 hours or 1 week prior to extended storage durations of 4, 6, or 8 weeks. Holding stems at 4 °C for 1 week prior to extended storage reduced vase life of all species. Rose stems remained viable after 8 weeks of extended storage when held at -0.6 °C, but only when no pre-storage hold was used. Lily and rose stems were not viable beyond 4-week storage durations when held at 4 °C, but remained viable with no pre-storage holding period after 8 weeks at -0.6 °C. Carnation stems maintained longer vase life irrespective of a pre-storage holding period when stored at -0.6 °C. Through this work we show that that many species of cut flower may be held at sub-zero temperature with improved or comparable vase life to the industry standard of 4 °C.
