Effects of growing environments, planting date, and stem treatments on sandersonia tuber weight and secondary tuber development

Abstract

Sandersonia (Sandersonia aurantiaca Hook) tuber growth and secondary tuber development were assessed in two growing environments (a greenhouse and outdoors), at three planting dates (1 October, 1 December, and 1 February) and with six stem pruning treatments. Tubers of c. 1 g were used. The pruning treatments consisted of cutting the stem just above the second flower when 50% of the stems had the second flower open, or 2, 4, 6, and 8 weeks later. In another experiment the effect of stem tipping, stem pruning, flower removal, and an auxin transport inhibitor (2,3,5‐triiodobenzoic acid (TIBA)) applied 3 weeks after the second flower opened were assessed. Tuber growth and secondary tuber development were affected by the date of planting, with both tuber weight and incidence of secondary tubers declining significantly in the later planting dates. Environmental factors including temperature, radiation, and day length may have influenced the rate and type of tuber growth. Stem pruning, removal of the growing tip plus flowers, or applying TIBA reduced secondary tuber numbers and had little effect on tuber size. This study suggests that it is possible to reduce the presence of undesirable secondary tubers by manipulating the growing environment or by developing appropriate cultural practices.