Effects of photoperiod,light source and growth regulators on the growth and flowering of Trachelium caeruleum

Summary

Experiments were conducted to determine the appropriate photoperiod, light intensities and sources, and growth regulators, necessary to produce Trachelium caeruleum as a commercially acceptable potted plant. T. caeruleum behaved as an LDP with a critical photoperiod of 14 h necessary for flower initiation but was day neutral for subsequent flower development (from macroscopic bud visibility to anthesis). Providing long days by daylength extension using metal halide (MH) lamps to provide high irradiance resulted in significantly earlier flowering and more flowers than using either MH or incandescent lamps at low irradiance. The use of incandescent lamps to extend the day resulted in slower flowering and fewer flowers than using MH lamps at the same irradiance. Daminozide was effective for controlling plant height but ancymidol and chlormequat were ineffective. Removal of the terminal bud resulted in more compact plants, and more blooms per plant, but delayed flowering by approximately one week.