Postharvest Handling of Cut Campanula medium Flowers

Various postharvest treatments were evaluated for effect on longevity and quality of cut Campanula medium L. ‘Champion Blue’ and ‘Champion Pink’ stems. Stems stored at 2 °C either wet or dry had no difference in vase life or percent flowers opened; however, flowers stored dry had a slightly greater percentage of senesced flowers at termination. Increasing storage duration from 1 to 3 weeks decreased vase life. Stems pretreated for 4 hours with 38 °C floral solution (deionized water amended to pH 3.5 with citric acid and 200 mg·L–1 8-HQC) or a 1-MCP pulse followed by a 5% sucrose pulse solution produced the longest vase life (10.3 or 10.4 days, respectively). Flowers opening after treatments commenced were paler than those flowers already opened and a 24-hour pretreatment with 5% or 10% sucrose did not prevent this color reduction. Stems had an average vase life of only 3.3 days when placed in floral vase foam but lasted 10.0 days without foam. Optimum sucrose concentration was 1.0% to 2.0% for stems placed in 22 °C floral vase solution without foam and 4% for stems placed in foam. High (110 μmol·m–2·s–1) or low (10 μmol·m–2·s–1) light levels did not affect postharvest parameters, but the most recently opened flowers were paler under low light conditions than under high light conditions. Chemical names used: 8-hydroxyquinoline citrate (8-HQC); 1-methylcyclopropene (1-MCP). Received for publication 1 Aug. 2001. Accepted for publication 7 Dec. 2001. Approved for publication by the Director, Oklahoma Agricultural Experiment Station (OAES). Our research was supported in part by OAES under project H-2119. We thank Leah Aufill for technical assistance and Sakata Seed America for financial support and flowers. Graduate Research Assistant. Professor; currently at Dept. of Horticultural Science, North Carolina State Univ., Campus Box 7609, Raleigh, NC 27695-7609. Specialty cut flowers have been growing in popularity with the industry and consumers for the last several years [U.S. Dept. of Agriculture (USDA), 2000]. Carnations (Dianthus caryophyllus L.), chrysanthemums [Dendranthema ×grandiflora (Ramat.) Kitam.], and roses (Rosa L.), which have been the mainstay of the cut flower industry for years, were “down sharply” in 1999 as part of a continuing trend (USDA, 2000). Continued success of specialty cut flowers requires the introduction of new species. Campanula medium, commonly known as Canterbury bells, is a biennial plant commonly used in gardens in the United States and sold as flowering potted plants in Europe (Dole and Wilkins, 1999). Flower color is blue or lavender, pink, and white. The inflorescence is a raceme of 2.5-cm-long, cup-shaped flowers creating an unusual shape not common in cut flowers (Fig. 1). One to several inflorescences of up to 75 cm long arise from pubescent plants with rosulate lower leaves; each inflorescence has 10 or more flowers (Fig. 2). ‘Champion Blue’ and ‘Champion Pink’ were bred specifically for cut flower production. They have a short crop time, typically flowering in 18 to 23 weeks, making it possible to grow and sell this normally biennial plant in a cost-effective time period (Cavins, 1999). However, limited research has examined the postharvest life of cut Campanula flowers (Sakata Seed America, personal communication). Storing cut Campanula stems in coolers benefits the grower, wholesaler, and florist by extending the production season, allowing storage of excess production, improving production efficiency, and enabling long-term shipment (Goszczynska and Rudnicki, 1988). Recommended storage temperatures for cut flowers depend on the particular species and cultivar, but generally vary between 0 and 4 °C (Nowak and Rudnicki, 1990). Cut Campanula stems could either be stored wet in water or preservative solution or dry in a polyethylene plastic or wax-lined box (Nowak and Rudnicki, 1990). Vase life can be extended by pretreatments and pulses, which are short-term treatments (generally 24 h or less) conducted just after harvest. A pretreatment may consist of placing stems in heated water (≈38 °C) to enhance water absorption or applying an anti-ethylene compound, such as silver thiosulfate (STS) or 1-MCP (Serek et al., 1995). Cut Campanula stems are sensitive to ethylene, which causes open petals to brown and shrivel and buds to discolor and die, and anti-ethylene compounds may prevent ethylene damage (Hunter et al., 2001; Woltering and van Doorn, 1988). Cut Campanula stems may benefit from the addition of sucrose to increase rate and number of Campanula buds opening, improve petal coloration, especially for the dark purple cultivar ‘Champion Blue’, and extend vase life (Halevy and Mayak, 1979; Nowak and Rudnicki, 1990; Sacalis, 1993). Sucrose can be applied in pulse solutions of 0.5% to 25% from a few hours to 2 d (Goszczynska and Rudnicki, 1988) or in vase solutions of 0.5% to 7%. With the presence of sucrose, addition of a germicide such as 8-HQC is necessary to inhibit microbial growth (Sacalis, 1993). Not only is 8-HQC effective against microbes, it is also slightly acidic, which benefits water absorption (Sacalis, 1993). Low light conditions after harvest can reduce flower color development in certain species. Incomplete coloration of petals has been correlated with purple cultivars of Eustoma grandiflorum Griese. under low light conditions after stem harvest (Griesbach, 1992; Kawabata et al., 1995). Campanula ‘Champion Blue’ also has purple petals, and high light intensity in the postharvest environment may enhance petal coloration. Fig. 1. Campanula medium flowers. Fig. 2. Campanula medium ‘Champion Pink’ inflo-