If the new shoots grow another 5 inches before late August, repeat the process. Pruning shapes the plant to form an attractive compact growth. Beginning Sept. 25, poinsettias need complete darkness from 5 pm to 8 am daily. Lights from any lamps will prevent normal flowering of an uncovered plant. Shorticulture days and 60-65 F night temperatures are essential for good bract development.
Poinsettias bloom according to day length.
Varieties are grouped according to the amount of time between shorticulture days and the appearance of colored bracts. Cultivars such as Amy and Lady will bloom about eight weeks after the onset of shorticulture days. Other cultivars may respond differently. Euphorbia pulcherrima is a native to the area around Taxco, Mexico, and was introduced to the United States by Joel R. Poinsett, the first United States ambassador to Mexico. The poinsettia flowers are actually small and inconspicuous.