Waters that originate in ponds, wells, etc. are more variable in quality and require periodic testing to assure they are acceptable for plant production and not contaminated with pathogens such as Pythium . Before starting a poinsettia crop, planning and research will help assure success. Many of the specifications needed to drive decisions about the crop come from understanding the target market for these plants. The characteristics required of this crop when sold through florists may vary from those sold through the chain store. Bracts , the colored leaves for which the plant is known, are modified leaves surrounding flowers that develop pigmentation in response to flower initiation.
Poinsettias initiate flowers when days become shorter than nights.
In the Northern Hemisphere, this day length condition naturally occurs during mid to late September and in the Southern Hemisphere, during March. Once short days begin, it is important that nights continue to get longer for bracts to form color. During this development stage of the poinsettia, if nights get shorter rather than longer the flowering will be disrupted and plants will fail to flower. The phase of growth prior to flower initiation is referred to as vegetative growth, while the flowering stage is known as the reproductive phase . The flowering response time is the time, usually in weeks, required for the plant to develop to a mature, salable flowering plant from the date of flower initiation.