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Lupinus havardii Wats. is a promising new specialty cut flower crop, but data on its greenhouse culture and management are limited. Two experiments investigated senescence-delaying activity of preharvest Ca fertilization and postharvest preconditioning with 1-MCP on L. havardii `Texas Sapphire' cut flower stems (racemes). In the first study, Ca (as CaCl2) was added to the nutrient culture solution at concentrations of 0, 2.5, 5.0, and 10.0 mm for 88 days in a greenhouse. Additional CaCl2 supply did not affect the total number of racemes produced per plant, the average number of flowers per raceme, or the retention of individual flowers on cut racemes over a 7-day vase period. However, Ca concentration in cut raceme tissues, ranging from 5.3 to 7.6 mg·g-1 dry weight, increased linearly with increasing Ca concentration in the nutrient solution, which was accompanied by a linear increase in average fresh weight retention per raceme and individual mature flowers (up to 7% above controls) during the 7-day vase period. In the second study under similar plant culture and vase conditions, 1-MCP applied at harvest resulted in an average fresh weight retention increase of 9% above controls during 7 days in the vase. Equivalent levels of desiccation in control racemes (loss in fresh weight retention) were delayed by 1.5 to 3 days in racemes with the highest Ca concentrations and those that had been preconditioned with 1-MCP. In view of the physiological significance of desiccation in cut flower quality loss, preharvest Ca fertilization and postharvest 1-MCP preconditioning may be useful techniques for delaying senescence and maintaining vase quality of cut L. havardii racemes. Chemical name used: 1-methylcyclopropene (1-MCP)
Historically, calendar date has been used to determine when cuttings are collected for rooting. However, year-to-year variations in climate limits the usefulness of using calendar date. More recently, rooting of stem cuttings has been associated with chilling accumulation. In the winter, daily temperatures in northern New Mexico can fluctuate from below freezing to well above freezing. Eight chilling accumulation models and calendar date were tested to determine the best predictor of rooting of white fir. The chilling accumulation models ranged from those based on number of hours at low temperatures to weighted models that calculated chilling unit accumulation and loss. In addition, temperature data based on 3-, 6-, 12-, and 24-hour averages were used. Most of the models were better than calendar date in predicting rooting. The best model was a weighted model that accumulated chilling from -5 to 10C with loss of chilling >15C and less than -10C. Other models that performed well included models that accumulated chilling from 0 to 7.2C, 0 to 15C, or -3.5 to 10C. On the average, the data based on 12-hour means was the best for modeling chilling accumulation to predict rooting.