Namaqualand ephemerals : phenology and thermal units

Abstract

The effect of different variables i.e. temperature, sowing date, water stress and achene age, on the phenology and the prediction of phenological stages of five Namaqualand ephemeral plant species were investigated. The species examined were Dimorphotheca sinuata, Foveolina albida, Heliophila seselifolia, Senecio arenarius and Ursinia caldlefolia. Later sowing dates and water stress resulted in smaller plants with relatively few open inflorescences at peak flowering and therefore a less spectacular flowering display. There were some differences in the phenology of plants derived from achenes collected at different times. The use of thermal units resulted in fairly accurate predictions of the timing of phenological stages such as peak flowering or even a spectacular flowering display for tourists. While cold units should be used until flower/inflorescence initiation, the combined use of cold and heat units are recommended in the prediction of later phenological stages.