Supplemental Lighting Quality Influences Time to Flower and Finished Quality of Three Long-Day Specialty Cut Flowers

Year-round demand for locally sourced specialty cut flowers continues to increase. However, due low radiation intensities and temperatures, growers in northern latitudes must utilize greenhouses, but limited production information detailing manipulation of the environment exists. Therefore, our objective is quantify influence supplemental lighting (SL) quality on time flower harvest stem three long-day flowers. Godetia ‘Grace Rose Pink’ (Clarkia amoena), snapdragon ‘Potomac Royal’ (Antirrhinum majus), stock ‘Iron Rose’ (Matthiola incana) plugs are transplanted into bulb crates placed one six greenhouse compartments with SL providing a total photon flux density 120 µmol·m−2·s−1 from 0700 1900 HR. After four weeks, extended provide 16 h photoperiod induce flowering. treatments provided by either high-pressure sodium (HPS) fixtures or various light-emitting diode (LED) fixtures. Treatments defined their 100 nm wavebands blue (B; 400–500 nm), green (G; 500–600 red (R; 600–700 far-red (FR; 700–800 nm) (photon μmol·m−2·s−1) as B7G60R44FR9 (HPS120), B20G50R45FR5, B20R85FR15, B30G25R65, B120, R120. Time (TTH) up 14, 15, 10 d slower under R120 godetia, snapdragon, stock, respectively, compared quickest (HPS120, B20R85FR15 SL). produces 18% longer than those grown treatments. Both broad-spectrum LED slightly delay TTH Stem caliper not commercially different between godetia although stems 14% thinner B120 other Flower petal color We recommend utilizing fixture spectrum similar they elicit desirable crop responses minimal developmental, quality, visibility tradeoffs. While HPS lamps perform similarly recommended fixtures, we LEDs higher efficacy potential energy savings.