I have not been able to find a lot of info on drying sunflowers for blooms; most is geared toward drying the seeds. Here is some info I did find- Cut when the flower is mature-the back of the flower is yellow, or the seeds are brown. Take water w/ you -they wilt easily. Cut when the petals are not fully open-they will open further when drying. Hang upside down in a dry, very warm area-they contain a lot of moisture and will mold if the area is not warm enough. Hope this helps some.