Stock Plant Management Techniques Affect Postharvest Flower Development of \u3cem\u3eImpatiens\u3c/em\u3e ×\u3cem\u3eHybrida\u3c/em\u3e

Stock plants provide a supply of unrooted cuttings for the asexual propagation of selected ornamentals. The primary goals of stock plant management are to maintain completely vegetative plants and to maximize shoot production. However, the result of producing vegetative cuttings can be slow production time, i.e., long production schedules for the greenhouse business that propagates and flowers the plants. Therefore, the first objective was to examine alternate methods of stock plant management in order to produce cuttings that flower in a shorter time period, e.g., 5-6 weeks from the start of propagation (“sticking”). Hybrid impatiens (Impatiens ×Hybrida) were used for this study. The second objective was to create a model to predict flower bud develop of hybrid impatiens so this tool could be used by growers to improve crop scheduling. The first experiment was a 3 x 5 x 6 factorial consisting of 3 levels of daily light integral (DLI) (low, medium and high), five levels of ethephon investigated (0, 50, 100, 200 or 300 mgL-1) and six stock plant node positions (NPSP). The NPSP represent different locations in the stock plant from which cuttings were harvested. The results showed that high levels of DLI in combination with low rates of ethephon, and higher NPSP resulted in cuttings that flowered in 5-6 weeks after harvest. A second study was designed to investigate the relationship between average daily temperature (ADT) and flower development of three cultivars of hybrid impatiens from the onset of a visible bud (2-mm in bud width). A flower bud development model was created using a four-parameter logistic equation that predicted time to flower based on the measured bud width of plants. Crops with a 3-mm bud width were predicted to flower in 31 d when grown in ADT of 18 °C, an increase in bud development occurred when ADT increased from 18 to 28 °C and the resulting time to flower decreased by 1 week. The usefulness of this model can be applied as a production tool for growers to flower crops for specific early or late marketing weeks which can be achieved through the manipulation of ADT