Euphorbia subg. Poinsettia 1858, but promoted to subgenus rank by Homer Doliver House in 1924. Recent studies have confirmed its monophyly. Its many species include: The common name "wild poinsettia" is sometimes applied to two of these species. Euphorbia subg. Poinsettia Euphorbia" subg. "Poinsettia is a subgenus deriving from the genus "Euphorbia", and is endemic to North America. <nowiki> </nowiki>It contains around 24 species, of which the best known is "E. pulcherrima", the poinsettia. This species grows wild in the mountains on the Pacific slope of Mexico, and despite many legends, no one is quite sure from which wild populations the cultivated varieties
Plant physiology Rather, a short day plant requires a minimal length of uninterrupted darkness in each 24-hour period (a short daylength) before floral development can begin. It has been determined experimentally that a short day plant (long night) does not flower if a flash of phytochrome activating light is used on the plant during the night. Plants make use of the phytochrome system to sense day length or photoperiod. This fact is utilized by florists and greenhouse gardeners to control and even induce flowering out of season, such as the "Poinsettia". Paradoxically, the subdiscipline of environmental physiology is on the one hand