Effects of storage temperature and duration on dormancy and flowering of Veltheimia bracteata

Veltheimia bracteata is a bulbous plant indigenous to South Africa. The plant is dormant in the summer and flowers in the winter. When there is enough rainfall in the summer it is an evergreen. In The Netherlands this crop is grown in greenhouses where the bulbs are planted in summer and flower from December until February. Primarily, we investigated whether sprouting of the bulbs during storage in the summer could be prevented. At the same time the growing cycle of the bulbs under greenhouse conditions was examined. In addition, the possibilities for long term storage in order to delay flowering was examined. It was found that flower formation started in May/June when seed on the plant was ripening and new roots appeared. Flower differentiation took place from June until October/November. Leaves were formed from July until October. Dormancy was influenced by storage temperature. Bulbs stored at 20°C were the first to sprout. At higher or lower temperatures it took longer before the bulbs sprouted. However storage at low temperature resulted in poor flowering or no flowering at all, whereas storage at high temperatures gave good results. Dormancy was also influenced by the time of harvesting. Lifting the bulbs before the seed was ripe (May) resulted in an increased period of dormancy compared to lifting two months later. Long term storage of the bulbs at 25°C was found to be suitable for extending the period of flower production. Planting bulbs in June/July resulted in flowering in December/January. Storing the bulbs at 25°C and planting them in March resulted in flowering in June/July. Planting later than March caused flower blasting at a late stage, probably caused by high greenhouse temperatures.