Photoperiod and Cold Treatment Regulate Flowering of Rudbeckia fulgida `Goldsturm'

Abstract

<jats:p>To determine the flowering requirements of <jats:italic>Rudbeckia fulgida</jats:italic> Ait. `Goldsturm', plants were grown under 9-hour photoperiods until maturity, then forced at 20 °C under one of seven photoperiods following 0 or 15 weeks of 5 °C. Photoperiods consisted of a 9-hour day that was extended with incandescent lamps to 10, 12, 13, 14, 16, or 24 hours; an additional treatment was a 9-hour day with a 4-hour night interruption (NI). Noncooled `Goldsturm' remained vegetative under photoperiods ≤13 hours, and essentially all plants flowered under photoperiods ≥14 hours or with a 4-hour NI. Flowering percentages for cooled plants were 6, 56, or ≥84 under 10-, 12-, or ≥13-hour daylengths and NI, respectively. Critical photoperiods were ≈14 or 13 hours for noncooled or cooled plants, respectively, and base photoperiods shifted from 13 to 14 hours before cold treatment to 10 to 12 hours following cold treatment. Within cold treatments, plants under photoperiods ≥14 hours or NI reached visible inflorescence and flowered at the same time and developed the same number of inflorescences. Fifteen weeks of cold hastened flowering by 25 to 30 days and reduced nodes developed before the first inflorescence by 28% to 37%. Cold treatment provided little or no improvement in other measured characteristics, such as flowering percentage and uniformity, flower number, plant height, and vigor.</jats:p>

Photoperiod and Temperature Influence Flowering Responses and Morphology of Tecoma stans

“…Numerous studies have shown the importance of providing inductive photoperiods to increase the flowering percentage in ornamental crops (Currey and Erwin, 2010;Karlsson and Werner, 2002;Mattson and Erwin, 2003;Rohwer and Heins, 2007;Runkle et al, 1999;Warner, 2010). For example, Currey and Erwin (2010) reported that Kalanchoe spp.…”

“…In our study, nearly all plants grown under 9-h photoperiods remained vegetative and only 30% of plants flowered under 12 h. The percentage of plants that had visible buds and flowered was greatest (100%) at 14-and 16-h photoperiods. Runkle et al (1999) reported that the number of nodes below the first inflorescence in black-eyed-susan (Rudbeckia fulgida var. sullivantii 'Goldsturm') decreased from 19.7 to 15.6 as the photoperiod increased from 14 to 24 h. Our data were in agreement, because plants under inductive 16-h photoperiods Table 2).…”

Effect of hydroponic and peat-free media in transplant production of Rudbeckia hirta varieties under different photoperiodic lighting and their photosynthetic parameters

“…Numerous Rudbeckia species and varieties have been reported in experiments of photoperiodic and flowering treatments: R. bicolor var. superba and R. speciosa (Murneek, 1940), Rudbeckia fulgida 'Goldsturm' (Runkle et al, 1999;Elkins & van Iersel, 2020) and Rudbeckia hirta (Beckwith, 1991;Blanchard & Runkle, 2010;Werner et al, 2011).…”