Effects of thermal regime on growth and flowering of Lisianthus cultivars

We investigated the effects of supplemental lighting on flowering of two double-flower cultivars of Lysianthus. The experiment was carried out in Scafati (Salerno), Italy (40°45' N, 14°32' E) in air-heated plastic greenhouses. Plants of the white cultivars Echo (for late autumn-winter transplanting) and Cessna (for late spring-summer transplanting) were transplanted on medium sandy soil on January 15 and grown under two lighting regimes, natural light (NL) and supplemental light (SL). Supplemental lighting was performed by extending the natural day length to 18 hours using High Pressure Sodium lamps. Under natural light conditions, the number of days to flowering was 113 in Echo and 130 in Cessna. Supplemental lighting anticipated flowering in both cultivars, with a stronger effect in Echo compared to Cessna (19 vs. 8 days earlier than the control, respectively) and reduced the length of flower stems.