The study examined the effects of light sources and light time on the growth and flowering responses of cut ‛Baekma’ and ‛Jinba’ chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitamura] under in vitro and greenhouse conditions in South Korea. In vitro shoot explants were treated with light-emitting diodes (LEDs) sources with white, red (660 nm), blue (450 nm), and red-blue for 5 wk. In a greenhouse experiment, 4-h supplemental lighting was provided with incandescent bulb, red LEDs, or white LEDs staining at 20:00, 22:00, 00:00, or 02:00 h, with 12 h of day length, for 8 wk in ‛Baekma’ and for 7 wk in ‛Jinba’, depending on their typical weeks to flowering. In vitro red LED treatments extended stems of ‛Baekma’ (2.9 cm) and ‛Jinba’ (3.7 cm) adventitious shoots. In the greenhouse, growth and flowering of ‛Jinba’ were little influenced by source and time of light. Total fresh weight (FW) and chlorophyll content of ‛Baekma’ flowers were high under white LEDs at 22:00 h in the greenhouse, resulting in successfully delayed flowering and enlarged flower size.