Effects of Temperature on Flowering of Agapanthus africanus HOFFMANNS

Abstract

The value of Agapanthus africanus as cut floweres has recently been recognized. There is now a need to study how to force the flowering time.
In this study, the growth periodicity of plants grown outdoors was clarified and the effect of temperature on the initiation and development of flower buds was investigated.
Shoot apices of plants grown outdoors were in the vegetative state in October and began to flatten and broaden in middle or late November. Following the initiation of spath leaves at year end, the growth of the apices ceased until early March, when the initial of first floret appeared. In early May, the first floret of an inflorescence reached the carpel primordia stage and the flower bud appeared outward amid the whorl of foliage leaves. Pollen formation occurred in early or middle June and anthesis was completed at the end of June.
Although flower formation was inhibited when the plants were placed at or above 20°C from September onwards, shifting to 10°C or 15°C caused them to initiate flower buds.
After flower initiation, the higher temperature resulted in earlier flowering, accompanied by some depression in flower size and scape length.
In a trial for commercial forcing, cropping of flowers in March, 3 month earlier than the natural flowering time, was attained by keeping plants at min. 20°C from the end of November onward. Application of long days of 16 hours, in addition, advanced the flowering.