I'm going to be growing sunflowers in a greenhouse and then transferring them to the Central Valley for a pollination research project, and have been having a hard time getting clear information on the timing of the flowering. I'm trying to get answers to the following questions for both the wild or common sunflower and the "sunspot" variety:

Does "days to flower" mean the days until the first flower begins to bloom from the planting day, or the days until the flower is fully bloomed? Which of these times corresponds to the flower beginning to be receptive to pollinators (ie: when are the florets open)? How long will the florets be open for?

thanks!!! any information will be incredibly helpful!