Light Intensity, Photoperiod, and Temperature Effects on Growth and Flowering of Red Firespike

The effects of light intensity and temperature on flowering and growth characteristics of potted red firespike (Odontonema strictum) were examined in two experiments. In Experiment. 1, plants were grown under 0%, 45%, or 65% shade under two photoperiod conditions; long-day (LD) and short-day (SD). Plants grown under 45% shade and LD were tallest at 35.9 cm while plants grown under 65% shade and SD were shortest at 22.8 cm. No shade and 45% shade in both LD and SD resulted in a greater number of inflorescences; 9, 7, and 6, respectively. The first open flower was observed in the no shade control after 92 days. In Experiment 2, plants were grown in controlled environment chambers with constant temperature set points of 15 °C, 25 °C, and 35 °C and an irradiance of 150 µmol·m^-2·s^-1 for 9 hours/day. Plants grown in 25 °C had the greatest height (49.2 cm) and largest leaf area. Plants grown in 15 °C and 35 °C had 28% and 22% less leaf area, respectively. The average number of inflorescences in plants grown at 25 °C was 1.6 while no inflorescence development was observed in plants grown at 15 °C or 35 °C by termination of the experiment. There were no differences between plant growth index or branch numbers due to temperature.