Gibberellic acid affects growth and flowering of Philodendron 'Black Cardinal'

A single foliar spray of gibberellic acid (GA(3)) at concentrations of 125, 250, 500, or 1,000 mg L-1 induced flowering of Philodendron 'Black Cardinal' (an interspecific hybrid developed from a series of crosses among P. wendlandii, hastatum, erubescens, imbe, fragrantissimum, and an unnamed species) in approximately 170 d. Percentage of plants induced and mean flower number per plant increased as GA(3) concentrations increased. Compared to unsprayed plants, the number of new leaves decreased, petiole lengths of new leaves and length of the largest leaf increased, but leaf width was unaffected among sprayed plants. One hour before the spathe started to unfurl, spadix temperatures increased, and temperatures in the male portion of the spadix rose by 10degreesC above ambient as the spathe fully opened. Elevated temperatures were recorded for about two hours and returned to ambient within five hours. Spathes remained open for about five hours. A creamy white spadix with a contrasting burgundy spathe resulted in more aesthetically pleasing plants than with foliage alone. Because of the short period of display, the open spathe would not increase additional ornamental value of Philodendron 'Black Cardinal' in the marketplace. However, if breeding is the purpose of flowering induction, spathes should be cut away from the spadix to facilitate pollination.