Flowering Habit and Photoperiodic Flowering Response of Stevia (Stevia rebaudiana Bertoni) in the Philippines

Stevia is a perennial shrub commercially cultivated for the sweet-tasting compounds known as steviol glycosides (SVglys). SVglys are extracted from the green leaves, thus maintenance of vegetative growth is critical in stevia production. This study was conducted to describe the flowering habit and response of potted stevia plants to different photoperiods under Philippine conditions. Photoperiodic treatments (10, 11, 12, 13, and 14 h) were provided using light chambers. Stevia has both terminal and axillary flowering habits. It has five white florets enclosed in a capitulum and exhibits an opposite branching pattern. Results showed that stevia is a facultative short-day plant with a critical daylength of about 12 h. Earlier and more profuse flowering was observed in plants exposed to photoperiods less than 12 h. Earliest flowering response was in 10 h photoperiod which occurred 10 d after light treatment, while flowering time was extended to 23 d in the 14 h photoperiod. Plants subjected to the 10 h photoperiod had the largest number of flowers (34 flower clusters or capitula), while the most number of leaves (37 leaves) was recorded in the longest photoperiod treatment. The study also established that stevia under a 10 h photoperiod requires 10 inductive cycles to induce flowering. Photoperiod was found to have significant positive correlations with the number of nodes and flowering time.