Plant response to ethephon treatment was tested on 27 cultivars of vegetative annuals that have spreading and trailing growth habits. A control treatment was compared to 500 and 1000 mg·L-1 (ppm) foliar spray treatments of ethephon. Plant height and/or width index were significantly reduced for 81% of the cultivars tested. Responsive cultivars were alternanthera (Alternanthera dentata), brachyscome (Brachyscome iberidifolia) `Toucan Tango'; calibrachoa (Calibrachoa hybrids) `Colorburst Red', `Million Bells Cherry Pink', and `Trailing Pink'; diascia (Diascia × hybrida) `Sunchimes Rose' and `Red Ace'; double impatiens (Impatiens wallerana) `Tioga Red' and `Tioga White'; sweetpotato vine (Ipomoea batatas) `Sweet Caroline Bronze'; lantana (Lantana camara) `Patriot Cherry' and `Samantha'; nemesia (Nemesia × hybrida) `Aromatica Dark Lavender', `Blue Bird', and `Blueberry Sachet'; nolana (Nolana paradoxa) `Blue Eyes'; ivy geranium (Pelargonium hybrida) `King of Balcon'; petunia (Petunia × hybrida) `Cascadia Pink', `Mini Bright Pink', and `Supertunia Mini Purple'; bacopa (Sutera cordata) `Bridal Showers'; and vinca vine (Vinca minor) `Illumination'. Ethephon was not effective on monopsis (Monopsis unidentata) `Royal Flush', persicaria (Persicaria microcephala) `Red Dragon', or calibrachoa `Liricashower Rose'. Different cultivars of petunia showed varied responses to ethephon treatments as did trailing snapdragon (Antirrhinum majus) `Chandelier Yellow' and `Luminaire Yellow'. Flower number was reduced in 55% of the cultivars due to a delay in flowering. The experiment finds efficacy of ethephon for most cultivars treated at rates greater than or equal to that used commercially, however more research is needed to determine optimum concentrations for the specific cultivars. Chemical name used: ethephon [(2-chloroethyl) phosphonic acid].
Terri W. Starman, Melissa C. Robinson, and Kristen L. Eixmann
Terri W. Starman, Shannon E. Beach, and Kristen L. Eixmann
Twenty-one cultivars from nine species of vegetative annuals were grown under optimum greenhouse production practices until maturity. At harvest, they were subjected to 0, 1, or 2 days of simulated shipping. After shipping, plants were rated for quality, and flower abscission was counted postship and weekly for 3 weeks in a simulated retail environment. There were few decreases in flower number and quality directly postship, but decline symptoms became evident as time lapsed in the postharvest environment. Flower abscission resulting from increased shipping duration occurred on ‘Sun Chimes Coral’ diascia (Diascia ×hybrida) and ‘Aromatica White’ nemesia (Nemesia ×hybrida). During the postharvest evaluation, ‘Dreamtime Copper’ bracteantha (Bracteantha bracteata), ‘Superbells Trailing Blue’ calibrachoa (Calibrachoa hybrid), ‘Aromatica White’ nemesia, and ‘Candy Floss Blue’ sutera (Sutera cordata) were the only cultivars to abscise all flowers (<0.4 flowers) by the end of the first week. Five cultivars still had flowers at termination of the experiment. Of these five, four were bracteantha cultivars including ‘Florabella White’, ‘Florabella Gold’, ‘Dreamtime Cream’, and ‘Sundaze Golden Yellow’, and ‘Cascadias Pink’ petunia. After 2 weeks postharvest, 12 of the 21 cultivars that were shipped 1 or 2 days did not have a high enough quality rating (<3.0 points) to be considered marketable. Each species in this study had one or two postharvest decline symptoms common to all cultivars of that species. However, cultivars within species also varied in their postharvest decline symptoms and longevity. More optimum environmental conditions, better care, and faster turnover in the retail market are needed to improve shelf life of vegetative annuals sold in containers.
Shannon E. Beach, Terri W. Starman, Kristen L. Eixmann, H. Brent Pemberton, and Kevin M. Heinz
Twenty-one cultivars of vegetative annuals were treated with 0%, 50%, or 100% of the production fertilization rate of 300 mg·L−1 N starting 2 weeks before and continuing until harvest. At harvest, plant width, flower number, and quality rating were measured. The plants were then placed in a simulated interior environment where flower number was counted and quality rating was assigned to each plant weekly for 3 weeks. Overall, 14% of the cultivars maintained a marketable quality (i.e., quality rating of ≥3.0 of 5) for 3 weeks, 43% for 2 weeks, 38% for 1 week, and one cultivar did not maintain quality during the postharvest evaluation. Reduced end-of-production fertilization rate (EPFR) resulted in higher quality ratings for at least one additional week of simulated shelf life for three cultivars, including ‘Dreamtime Copper’ bracteantha (Bracteantha bracteata), ‘Vanilla Sachet’ nemesia (Nemesia ×hybrida), and ‘Bridal Showers’ sutera (Sutera hybrida). ‘Comet White’ and ‘Sunlight’ argyranthemum (Argyranthemum frutescens) retained flowers an additional 2 weeks and ‘Caritas Lavender’ angelonia (Angelonia angustifolia), ‘Dreamtime Copper’ bracteantha, ‘Liricashowers Deep Blue Imp.’ and ‘Starlette Trailing Purple’ calibrachoa (Calibrachoa hybrid), ‘Vanilla Sachet’ nemesia, ‘Cascadias Pink’ petunia (Petunia ×hybrida), and ‘Bridal Showers’ sutera retained flowers an additional 1 week when treated with 0% compared with 50% or 100% EPFR. Four cultivars had decreased plant width at harvest with 0% EPFR. These results indicate that reducing fertilization 2 weeks before harvest can prolong shelf life of some vegetative annuals. Differences in the length of shelf life and responses to reduced EPFR occurred among cultivars of all the affected species. Reduced EPFR did not increase the shelf life of two species, including diascia (Diascia ×hybrida) and lantana (Lantana camara).