Production and postproduction studies with potted sunflowers

Abstract

Sunflower (Helianthus annuus) has potential as a potted flowering plant due to short crop time, ease of propagation, and attractive flowers but postharvest life is short and plants can grow too tall. Days from sowing to anthesis differed significantly among six sunflower cultivars and ranged from 52 days for 'Big Smile' to 86 days for 'Elf' and 'Pacino.' Height ranged from 6.0 inches (15.2 cm) for 'Big Smile' to 14.9 inches (37.8 cm) for 'Pacino', postproduction life ranged from 10 days for 'Elf' and 'Pacino' to 15 days for 'Big Smile', and postproduction chlorosis ratings (1 to 5, with 5 the least) ranged from 5.0 for 'Teddy Bear' to 4.4 for 'Big Smile' after 5 days and 4.2 for 'Teddy Bear' to 3.1 for 'Sunspot' after 10 days. Promalin (a gibberellin and benzyladenine mixture) applied at 62.5 to 500 ppm (mg·L-1) was not commercially useful in extending postproduction life. Increasing pot size from 4 to 6 inches (10 to 15 cm) in diameter decreased postproduction life and plants in 5-inch-diameter (13 cm) pots were tallest. Pots with three plants flowered more quickly than those with one or five plants and pots with five plants had 1 day shorter postharvest life than those with one or three pots. All cultivars were facultative short-day plants, except for 'Sundance Kid', which was day neutral. Storing potted sunflowers at 41°F (5°C) for 1 week did not reduce postproduction life, which was 11 to 12 d; however, 2 weeks of cold storage resulted in foliar damage. Three cultivars were found to be most suitable for pot production, 'Elf', 'Pacino' and 'Teddy Bear', with one or three plants per 6-inch pot and sprayed with daminozide (B-Nine) at 8,000 ppm, or drenched with paclobutrazol (Bonzi) at 2 mg/pot (a.i.) (28,350 mg = 1.0 oz).