2018 ASHS Annual Conference

Cut dahlia (Dahlia Cav.) flowers are perennially popular with consumers and command a relatively high per-stem price. Due to their short postharvest longevity, growers are always seeking ways to extend dahlia vase life for consumers. Pulsing cut flowers with plant growth regulators achieves this goal in species such as alstroemeria, carnation, gladiolus, and iris. Gibberellic acid (GA) delays flower wilting and senescence in some species and is an antagonist to abscisic acid, which promotes those processes. Cytokinins can extend vase life of some cut flowers and has been shown to do so in a few dahlia cultivars. We investigated the influence of pulse treatments of benzyladenine (BA), GA₄₊₇, and the commercial solutions Fresco^® and Chrysal BVB on vase performance of dry-shipped, cut dahlias ‘Amora’, ‘Natalie G’, and ‘Prospero’. Fresco^®, which provides equal amounts of both BA and GA₄₊₇ at the concentrations indicated in one solution, was used at 5, 10, 20, 30, and 50 mg‧L^-1. The five other treatments were 20 mg‧L^-1 BA, 20 mg‧L^-1 GA₄₊₇, 2 mg‧L^-1 Chrysal BVB, combined 20 mg‧L^-1 Fresco^® and 2 mg‧L^-1 Chrysal BVB, and tap water control. Fresh-cut stems were pulsed for 24 h in a 5 °C cooler before placing them into vases for consumer vase life determination. Most of the variables assessed were not influenced by the pulse treatments: solution uptake during pulse treatment, water uptake while in vase, change in vase water pH or EC, stem fresh weight change or dry weight at termination. Fresco^® increased vase life (by 35% across cultivars) and flower quality after 4 days in vase compared to tap water in all three cultivars, and 5 mg‧L^-1 (‘Natalie G’, ‘Prospero’) or 10 mg‧L^-1 (‘Amora’) were as good as or better than higher concentrations. Pulsing flowers with 2 mg‧L^-1 Chrysal BVB did not improve vase life or flower quality after 4 days in vase compared to tap water, and adding it with 20 mg‧L^-1 Fresco^® could negate the benefit of Fresco^®. Depending on the cultivar, the increased vase life and/or higher flower quality after 4 days in vase achieved by using Fresco^® was seen with BA alone, GA₄₊₇ alone, or neither plant growth regulator on its own.