Evaluation of key horticultural traits for Ptilotus nobilis in sub-tropical regions

Plants belonging to the genus Ptilotus have immense potential to be developed for the floricultural industry. Many of these plants flower profusely and have potential as cut focal flowers, cut fillers, potted colour or for use in landscape design. Ptilotus nobilis plants produce numerous fragrant cream to pink coloured inflorescences, which exhibit a long vase-life adding to their value as a cut-flower crop. As yet, there is no information published on the key horticultural traits for this species. This work undertook greenhouse trials to evaluate the floricultural attributes for P. nobilis collected from the Cunnamulla region in western Queensland, Australia. As a potted colour crop, P. nobilis may be marketed as a short lived perennial with plants flowering continuously for more than 2 years. From a cut-flower perspective, each plant produced an average of 11 flowering stems per month during December to April, and 8 flowering stems per month during May to August. Flowering stem length and inflorescence length averaged 35.4 and 7.2 cm, respectively for the period November to April, versus 39.2 and 6.3 cm stem and inflorescence lengths, respectively during May to August. As flowering stem lengths range from 17 to 79 cm, there is scope for selection of tall forms for cut flowers and compact forms for potted colour. Furthermore, the harvest duration of flowering stems averaged 43.5 days highlighting the durability of P. nobilis as a cut-flower product. A minimum thermal requirement of 623 growing degree days (GDD) were required to reach flowering after pruning with a predicted base temperature of 0.5 °C and maximum temperature of 18.2 °C when grown in a greenhouse at Gatton, Queensland, Australia. Further work needs to investigate the flowering physiology in response to temperature, photoperiod and light intensity to determine whether flowering can be predicted for different production regions. Also, vegetative propagation methods and field cultural requirements require further investigation to progress the commercial development of this new product.