Daily Light Integral, Prevernalization Photoperiod, and Vernalization Temperature and Duration Control Flowering of Easter Cactus

Abstract

Experiments were performed on Hatiora gaertneri (Regel) Barthlott ‘Jan’ and ‘Rood’ and H. ×graeseri (Wedermann) Barthlott ‘Evita’ to determine their flowering responses to 1) daily light integral (DLI) before and during vernalization; 2) 0 to 6 weeks of short-day (SD) or long-day (LD) photoperiods before vernalization at 10, 12.5, or 15 °C; 3) propagation from April to July; 4) timing of leveling before or during inductive treatments; and 5) SD photoperiods before vernalization under darkness at 0 to 10 °C. ‘Jan’ grown under elevated DLI before vernalization and low DLI during vernalization flowered more prolifically than plants grown under low DLI before vernalization or high DLI during vernalization at 15 °C. Six weeks of SD photoperiods before vernalization increased the number of buds per flowering phylloclade after vernalization at 10 °C and increased flowering uniformity when vernalization duration was insufficient at 10 °C or vernalization temperature was 12.5 or 15 °C. For plants flowering in January, propagation the previous April produced better flowering than propagation in May, June, or July. Removal of apical phylloclades during prevernalization SD or during vernalization was deleterious to flowering. Vernalization in the dark produced marginal flowering, but SD treatment before vernalization increased the percentage of apical phylloclades flowering, buds per flowering apical phylloclade, and percentage of plants flowering after dark vernalization. ‘Evita’ flowered more poorly than either ‘Jan’ or ‘Rood’. Collectively, the most uniform flowering in January occurred when plants were exposed to a sequence of 4 to 6 weeks of SD, vernalization at 7.5 to 15 °C for 8 weeks, then growth under LD for 7 weeks.