Modulation of Flowering Time in Poinsettia (Euphorbia pulcherrima) Using Environmental and Chemical Cues

Abstract: Poinsettias (Euphorbia pulcherrima) are cherished indoor plants recognized for their vibrant bracts that enhance indoor aesthetics during the winter season. As a photoperiod-sensitive crop that flourishes under short days, poinsettias naturally bloom during longer nights, enabling nurseries to trigger flowering in time for the winter festivities. Effective management of the crop includes the application of growth regulators, pruning, adjustments in temperature and light intensity, and proper water management to promote healthy growth and optimize yield. Flower bud formation in poinsettias begins when nights reach about 11 hours and 50 minutes of darkness, roughly around September 25th. It is advisable to maintain night temperatures between 68 and 70°F during the period of floral initiation, as temperatures exceeding 73°F may postpone blooming. Different cultivars need different levels of sun and darkness to produce their usual red leaves; early ones need sun for 8 hours accompanied by darkness of 16 hours, mid ones demand 10 hours of sun and 14 hours of darkness, whereas late ones require 12 hours of both. Keywords: Asthetic, Photo-period, Short Day, Yield and Blooming References: • Alden, MA. and Faust, JE. (2022). Determining the Optimum Night Length for Flower Development in a Modern Poinsettia Cultivar. Hortscience, 57(2), 273–276. • Batelja, K., Goreta Ban, S., Dumičić, G. and Perica, S. (2009). Effect of photoperiod, cultivar and number of lateral shoots on vegetative growth and flowering of poinsettia. 26, 55–62. • Evans, MR., Wilkins, HF. and Hackett, WP. (1992). Meristem Ontogenetic Age as the Controlling Factor in Long-day Floral Initiation in Poinsettia. Journal of the American Society for Horticultural Science, 117(6), 961–965. • Joiner, JN. and Harrison, DD. (1967). Control of Growth and Flowering of “Paul Mikkelsen” Poinsettias by Photoperiod and Growth Retardants. 80, 416. • Larson, RA. (1980). Introduction to Floriculture. Academic Press Inc. New York. • Prasad, KS. (2022). Effects of Selected Pinching Dates and Lighting Regimes on Several Aspects of Poinsettia Quality. • Smith, CA. (1980). Effects of Selected Pinching Dates and Lighting Regimes on Several Aspects of Poinsettia Quality. • Zhang, M. and Runkle, ES. (2019). Regulating Flowering and Extension Growth of Poinsettia Using Red and Far-red Light-emitting Diodes for End-of-day Lighting. Hortscience, 54(2), 323–327.

Keywords: Asthetic, Photo-period, Short Day, Yield and Blooming

Author: Mansi Mishra, Meenakshi Basoli, Kajol Chauhan, Sakshita Sandhu, Srishty Kumari, Swati

doi: https://doie.org/10.10346/AE.2025175958

Reference: Alden, MA. and Faust, JE. (2022). Determining the Optimum Night Length for Flower Development in a Modern Poinsettia Cultivar. Hortscience, 57(2), 273–276. • Batelja, K., Goreta Ban, S., Dumičić, G. and Perica, S. (2009). Effect of photoperiod, cultivar and number of lateral shoots on vegetative growth and flowering of poinsettia. 26, 55–62. • Evans, MR., Wilkins, HF. and Hackett, WP. (1992). Meristem Ontogenetic Age as the Controlling Factor in Long-day Floral Initiation in Poinsettia. Journal of the American Society for Horticultural Science, 117(6), 961–965. • Joiner, JN. and Harrison, DD. (1967). Control of Growth and Flowering of “Paul Mikkelsen” Poinsettias by Photoperiod and Growth Retardants. 80, 416. • Larson, RA. (1980). Introduction to Floriculture. Academic Press Inc. New York. • Prasad, KS. (2022). Effects of Selected Pinching Dates and Lighting Regimes on Several Aspects of Poinsettia Quality. • Smith, CA. (1980). Effects of Selected Pinching Dates and Lighting Regimes on Several Aspects of Poinsettia Quality. • Zhang, M. and Runkle, ES. (2019). Regulating Flowering and Extension Growth of Poinsettia Using Red and Far-red Light-emitting Diodes for End-of-day Lighting. Hortscience, 54(2), 323–327.

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