Propagation, height control, and flowering of Hypoestes phyllostachya
Seeds of Hypoestes phyllostachya Bak. (polka-dot plant) did not require light to germinate. Sowing method did not affect germination percentage and seedling fresh weight. Bottom heat (24 ± 2°C) promoted seedling growth but did not enhance germination. Stem cuttings did not require bottom heat or rooting hormone to induce adequate adventitious root formation. Three-node cuttings rooted more rapidly and had a more extensive root system than two-node cuttings. Cuttings stuck at a density of 200 per flat rooted less vigorously than those stuck at a density of 135 or 150 per flat. When unrooted cuttings were placed directly into 10 cm pots, root systems were more extensive on cuttings stuck one per pot than on cuttings stuck three per pot. Under intermittent mist, cuttings rooted more extensively than when covered with clear plastic domes. Cultivar differences were observed within both seed and cutting treatments.
The optimal concentrations of ancymidol, chlormequat, ethephon, paclobutrazol, and uniconazole to inhibit shoot growth and internode elongation of H. phyllostachya were determined and found to be similar for both seed- and cutting-propagated plants. Daminozide, even at 6000 mg-liter- 1 , was ineffective. Two applications of chlormequat at 1000 mg-liter- 1 resulted in similar height control as one application of 3000 mg.liter- 1• Chlormequat and paclobutrazol are less expensive and were more effective than ancymidol. White cultivars showed greater increase in plant height but less increase in growth index than pink and red ones.
Hypoestes phylloslachya was found to be a quantitative (or facultative) short day plant. Seed-propagated plants which attained 16 nodes flowered regardless of photoperiod, but flowering was more rapid under short day than under long days. When applying ethephon at high concentrations, percentage of plants flowering decreased, flowering was delayed, the number of aborted flower buds increased, and most of the plants did not flower within 15 weeks of sowing. The optimal concentrations and time of application for control of flowering for both seed- and cutting-propagated plants were also determined. Plants which received two applications of ethephon at 1500 mg.liter- 1 had a lower percentage of flowering and a greater number of vegetative buds than those received one or no application.