The timing of the crop is probably the most important thing that Easter lily (Lilium longiforum thunb) forcers must accomplish, and the variable date of Easter complicates scheduling (6, 12). The influence of bulb maturity and treatments prior to being placed in the greenhouse, often not under the grower’s control, makes forcing a challenge (2, 11, 17). Several methods are used to monitor progress of the crop, but adjusting temperatures is the actual means of controlling the rate of growth and development. Measurements of time and temperature, expressed as heat units or degree-days, are used to monitor the growth and development of many crops (1, 13, 21) and to predict with a high level of precision certain stages of their development. Degree-days or heat units offer little advantage over time alone as indicators of crop progress under conditions where temperature can be controlled to eliminate or minimize variations. Variations in greenhouse temperatures, greater during daytime hours than at night, especially in southern U.S. locations, are largely responsible for timing problems with Easter lilies. Heat unit summations may be reliable indicators where such variations occur. There are apparently no reports of attempts to use heat units or degree-days to monitor Easter lily shoot development.
Phoenix roebelenii O’Brian palm seedlings were potted in Metro Mix 500, and 3 groups of 25 plants each were fertilized with 18–2.6–10 (8- to 9-month release), 19–2.6–10 (3- to 4 month release) Osmocote, and 21–2.6–10 (6-month release) Sulfur Kote. Control pots with and without plants were either fertilized or not fertilized. Seedling palms were greenhouse grown for 23 weeks at temperatures ranging from 18° to 41 °C. Fertilizer type had no significant effect on leaf number or length, total dry weight or root dry weight. Plants which received Osmocote formulations showed higher foliage dry weights than plants which received Sulfur Kote. Conductivity of leachate (EC = mmhos/cm2) from pots fertilized with slow-released materials generally increased with no indication that release rate of nutrients had peaked.
Young Phoenix roebelenii O’Brian palms (2–3 leaves) and older seedlings (6–9 leaves) were potted in Mott’s amended medium and grown for 42 and 20 weeks, respectively. Three rates of 18N–2.6P–10K Osmocote, 25N–3.9P–14K Peter’s soluble and Osmocote plus Peter’s soluble fertilizer were used as treatments. Controls were potted but not fertilized. All were greenhouse grown at temperatures varying between 18° to 46°C. Fertilizer types or rates had no significant effect on leaf length or dry weight. High rates of Osmocote, and, in some instances, middle to high rates of fertilizer combinations, increased leaf number significantly. Plants receiving all rates of fertilizer appeared larger and produced significantly more leaves than unfertilized plants.