Preparing containerized garden plants for postproduction stress and reducing stress during transport and retail is important to reducing financial losses for the grower and retailer. Pay-by-scan marketing dictates that growers are paid when the consumer buys their product. Therefore, reduced shrinkage during shelf life increases revenue. Improved quality in products purchased by the consumer leads to greater consumer satisfaction and encourages repeat purchasing.
Factors influencing shelf life of a crop begin during production (Jones, 2002). Fertility “hardening off” or “toning” is a production practice that has been shown to increase shelf life of a variety of flowering potted plants and foliage plants (Jones, 2002; Roude and Barrett, 1991). For greenhouse production of bedding plants, toning recommendations include reducing night temperature to 50 to 55 °F, reducing irrigation frequency, and reducing fertilization by at least one half at the time of visible bud (McCann, 1991).
Terminating fertilizer has not been widely used for bedding plants because in the past they had such small growing media volumes and little nutrient reserves to sustain them (Jones, 2002). Today, however, with the use of larger containers for marketing bedding plants, this practice needs to be reexamined. Many garden plants are being produced as vegetative cuttings, which require production in larger pots (i.e., ≥4-inch-diameter). The increased root substrate volume allowable in pots versus plugs and cell packs is conducive to increased postproduction longevity because more water can be held for a longer time so that plants do not dry out as quickly. Using larger pot sizes and different media choices are two ways growers can influence how plants will survive postproduction water stress (Jones, 2002).
Fertilizer toning by reducing production fertilizer rate throughout production or by decreasing or ceasing end-of-production fertilization rate for 3 weeks or more increased postproduction longevity of flowering potted plants and foliage plants. Higher-quality schefflera (Schefflera arboricola and Brassaia actinophylla) were maintained for 3 months in an interior environment (Brasswell et al., 1982), the shelf life of chrysanthemum (Dendranthemum grandiflorum) was increased by up to 7 d (Nell et al., 1989), and less bract necrosis occurred on poinsettia (Euphorbia pulcherrima) (Nell and Barrett, 1986). Decreased flower senescence occurred on campanula (Campanula carpatica) (Serek, 1990) and wax begonia (Begonia ×semperflorens-cultorum) (Conover et al., 1993), extending their shelf life.
Higher carbohydrate reserves improve a plant's chance of survival when it leaves the greenhouse and is moved to less-than-ideal postproduction environments (Jones, 2002). Excessive N supply during cultivation causes secondary salt stress, leading to decreased carbohydrate levels, coinciding with low photosynthetic capacity, and leading to postproduction carbohydrate deficiency (Druege, 2001). Nitrogen influences C allocation, and the concentration of sugar and starch is decreased with increased N supply. In addition, salt-stressed roots have higher carbohydrate requirement for maintenance of respiration (Druege, 2001).
Reducing production fertilization rate at the end of production has not been applied to vegetative annual garden plants grown in larger pots versus seed-propagated bedding plants grown in bedding plant flats. The objective of this study was to determine the effects of reduced end-of-production fertilization rate on plant width at harvest, flower abscission during shelf life, and postproduction quality of 21 cultivars of vegetative annuals.
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Conover, C.A., Satterthwaite, L.N. & Steinkamp, K.G. 1993 Production fertilizer and postharvest light intensity effects on begonias Proc. Florida State Hort. Soc. 106 299 302
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