Volatile fuel prices, an increased emphasis on sustainable production practices, and declining profit margins have motivated commercial growers of annual bedding plants to reduce energy inputs and improve crop scheduling accuracy. The objectives of this research were to quantify the influence of average daily temperature (ADT), photosynthetic daily light integral (DLI), photoperiod, and transplant size on the flowering characteristics of popular bedding plant crops. Increasing ADT from 14 to 26 oC decreased flowering time and plant quality in nearly all of the 18 species and varieties evaluated in one experiment. In a separate experiment, similar but variety-specific responses occurred in 16 petunia (Petunia ×hybrida) cultivars grown at 12 to 23 oC. Linear and non-linear mathematical models were developed under a range of DLI conditions to predict the influence of ADT on flowering time of these crops, and the base temperatures (Tmin) at which the flowering rates were zero were estimated. The estimated Tmin ranged from -3.9 oC for Diascia barberae to 13.8 oC for Gomphrena globosa. An additional study quantified the effects of transplant size and ADT on flowering time and estimated profitability of five species. Flowering time decreased only when the larger transplants contained more mature plants, but transplanting a larger propagule was not necessarily a profitable strategy. Finally, seedling sensitivity and duration of long-day induction, as well as the effects of temperature and photoperiod interaction on flowering, were determined in three petunia varieties.
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