Year-round demand for locally sourced specialty cut flowers continues to increase in the U.S., but growers in northern regions cannot produce them outdoors or in high-tunnels year-round due to poor environmental conditions during the winter and early spring. Thus, they must use greenhouses to maintain a proper lighting environment to capitalize on demand during these seasons. Our objectives for Expts. 1 and 2 were to a) determine how photoperiod influences morphology of marigold ‘Xochi’ (Tagetes erecta), witchgrass ‘Frosted Explosion’ (Panicum capillare), and dianthus ‘Amazon Rose Magic’ and ‘Amazon Neon Cherry’ (Dianthus barbatus interspecific) young and finished plants, and b) quantify how photoperiod and daily light integral (DLI) influence floral initiation and quality of witchgrass and dianthus. For Expt. 3, we sought to quantify how supplemental radiation quality influences floral initiation and finished quality of three long-day specialty cut flowers. Marigold was harvestable when young plants were grown under photoperiods ≥11 h or a 4-h NI, and finished under 12-h photoperiods. Witchgrass was harvestable when young plants were grown under photoperiods ≥14 h or a 4-h NI, and finished under photoperiods ≥14 h. Dianthus was harvestable when young and finished plants were grown under 9- to 16-h photoperiods, or a 4-h NI. Additionally, cut flowers should be grown under a DLI of ≥10 mol·m–2·d–1. Godetia, snapdragon, and stock cut flowers should be grown under supplemental light with a spectrum similar to B20R85FR15 or a broad spectrum, for desirable crop quality and minimal developmental, visibility, and energy tradeoffs.
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