FLOWERING OF STEVIA

Stevia (Piquerria trinervia), is a fragrant umbelliferous cut flower which was used extensively at the turn of the century in place of Gypsophilla.

Traditionally this crop was grown as a fall blooming cut flower with the production period extended by growing the plant at low temperatures.

To develop a year around flowering program, rooted cuttings were grown under either natural or artificial long days in a 16° glasshouse to maintain plants in a vegetative state. Plants were pinched to 4 nodes and then place under 8 hr natural days with incandescent day extensions from 1 to 8 hr. Plants grown under an 8 hr photoperiod produced a compact inflorescence with short peduncles which would be unsuitable as a cut flower. As the photoperiod increased to 12 hr the peduncle length increased. A photoperiod of 14 hr inhibited floral initiation with a 16 hr photoperiod maintaining the plants in a vegetative condition.

Plants grown under 8 hr short days then transferred to natural long days required one short day cycle to induce flowering although anthesis was delayed. After fourteen short day cycles, lateral shoots began to elongate. Eighteen short days were required to promote both rapid floral initiation and entirely reproductive lateral branches within the umbel.