`Florida Blue' Semi-dwarf Lisianthus [Eustoma grandiflorum (Raf.) Shinn.

Abstract

Lisianthus was introduced into the U.S. floricultural trade in the early 1980s. Although evaluated as a potential cut flower and potted plant (Halevy and Kofranek, 1984), introduced cultivars primarily were developed for use as cut flowers. They required high rates of plant growth retardants to make them suitable as potted plants (Starman, 1991; Tjia and Sheehan, 1986; Whipker et al., 1994). In the early 1990s, the dwarf cultivars Little Belle Blue, Blue Lisa, and Mermaid Blue were released to U.S. markets. These dwarf cultivars can be grown as potted plants without growth retardants. Although breeding efforts were successful in developing shorter plants, problems with heat-induced rosetting were similar to those with taller cultivars. Dwarf cultivars also rosette when grown at 25 to 28 °C (Harbaugh et al., 1992; Ohkawa et al., 1991). Rosetted plants have a basal cluster of leaves and very short internodes typical of biennials, and they do not bolt or flower for 3 to 6 months without exposure at ≤18 °C for 3 to 4 weeks to reverse heatinduced rosetting (Ohkawa et al., 1994; Pergola, 1992). Semirosetted plants develop when seedlings are grown at a constant 22 to 25 °C or at 28 °C days. Semirosetted plants have one or more side shoots that may elongate and flower, but plants flower unpredictably and are of poor quality. Thus, commercial production of lisianthus for late spring or summer sales as cut flowers or as potted plants is limited by high temperatures in many areas of the United States and other countries. Fall plug production, to produce flowering plants for early spring sales, is also impossible due to rosetting of plugs caused by the interaction of high temperatures and short days (Harbaugh, 1995). ‘Florida Blue’ is a heat-tolerant, semi-dwarf lisianthus developed at the Univ. of Florida’s Gulf Coast Research and Education Center, Bradenton. Seedlings have been produced at 28 to 31 °C without rosetting.