Application of plant growth regulators to singleLeucospermumstems to extend stem length

Abstract

To obtain high prices Leucospermum cut flowers are required to have long, straight and slender stems. In addition, the time of flowering is also important, with Nov. and Dec. being considered periods of high demand in Europe for Cape Flora products. Several cultivars grown commercially in South Africa are genetically inclined to produce shorter stems, whilst most late flowering cultivars from warm production areas also present a challenge to deliver sufficient stem length. The practice of disbudding to extend the marketing window, especially in warm areas, likewise results in shorter stems the following season. To increase the stem length plant growth regulators were applied to single stems of Leucospermum 'Succession II' and 'Soleil' at Arnelia Farms, Hopefield, South Africa. Seven treatments were applied at five different times following pruning, at two weekly intervals. Shoot growth was monitored, while the duration of the harvest period and inflorescence quality was also recorded. The stem length was found to have increased in stems of all treatments compared to the control, for both cultivars. In 'Succession II' five applications of the 100 mg L-1 benzyladenine (BA) and gibberellic acid (GA3) combination extended the stem length by 200 mm compared to the control. In 'Soleil' five applications of 500 mg L-1 GA3 was responsible for a 200 mm stem length increase. Treated stems differed distinctly from that of the control in that a more upright growth manner was observed. The timing of application of the respective growth regulators is however considered important to obtain the required results. The use of growth regulators has shown commercially potential to increase stem length in Leucospermum.