Controlling the flowering of Eucharis grandiflora Planchon with ambient and regulated soil temperature

Plants of Eucharis grandiflora Planchon which had enlarged bulb-meristems a t the end of 10 days treatment with 15 degrees C continued to develop flowe r buds when they were transferred to 30 degrees C, whereas some plants did not when transferred to 20 degrees C. Regardless of the growing temperature s at 20, 30 or 35 degrees C for 70 days prior to a chilling (15 degrees C), most of the plants flowered, indicating that a warm temperature (25-30 deg rees C) followed by a cool to moderate temperature (15-20 degrees C) is not essential for flower induction, although it promotes the development of ne wly formed axis. Based on these findings, an energy saving temperature sche dule for regulating soil temperature was developed; the soil was chilled at 15-18 degrees C for 10 days with or without subsequent heating at 25 degre es C or above, once in every 2 months. Plants on the soil without temperatu re regulation produced 1.1 flowering stems per bulb per year. Those produce d by plants grown on the soil chilled without subsequent heating and on the soil chilled followed by heating were 1.6 and 2.9, respectively. Practical implications of this temperature protocol are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.