| Flowering of temperate herbaceous perennials is often regulated by daylength (photoperiod) and low temperature (vernalization) to ensure reproductive success. Greenhouse growers manipulate photoperiod and vernalization to schedule flowering of herbaceous perennials for specific market dates. Our objective was to characterize the influence of vernalization on floral evocation and subsequent flowering characteristics of three herbaceous perennials. We also investigated the effect of photoperiod and photosynthetic daily light integral (DLI) on flowering of Coreopsis grandiflora 'Sunray'.; Following vernalization at -2.5 to 20°C for 0 to 12 weeks, Campanula 'Birch Hybrid' exhibited a near-obligate vernalization requirement and all flowering responses studied were affected by the vernalization temperature, duration and their interactions. The minimal and maximal cardinal temperatures for vernalization were <0°C and between 15 and 17.5°C, respectively. The optimal vernalization temperatures (Topt) depended on the flowering response assessed and ranged between 0 to 12.5°C for flowering percentage to 5 to 7.5°C for rate of progress to flowering. Therefore, all relevant flowering responses should be considered when developing and interpreting vernalization models.; Dianthus gratianopolitanus 'Bath's Pink' exhibited a facultative vernalization response to 0 to 10°C and did not vernalize at 15°C. Complete flowering was achieved following ≥4, ≥3 and 8 weeks at 0, 5 and 10°C, respectively. Vernalization temperature and duration affected time to anthesis, and number of nodes and flower buds and flowers at anthesis. Based on the minimum durations required to achieve maximum flowering response, the order of efficacy of vernalizing temperature was 5°C>0°C>>10°C.; Coreopsis grandiflora 'Sunray' exhibited a dual induction requirement for floral evocation. The primary induction was fulfilled by either vernalization or short days and secondary induction was stimulated by long days. Following sub optimal durations of primary induction treatment, vernalization was more effective in promoting floral evocation than short days. DLI influenced flowering percentage, percent reproductive laterals, time to anthesis, number of inflorescences, and plant height at anthesis. |
