I think both the striped and black oil varieties tend to grow mostly as large central stalks with large flowers. This is how they are grown and harvested for the bird seed and oil production. Individual plants may develop lots of side branches, especially if the main growing tip is damaged. I heard that the black oil ones grow the easiest. Supposedly, the birds really love them too.
Critters visiting the yard eat the leaves and flower heads before they are fully grown.
All I usually have left are leafless stalks. I use to blame the squirrels, but now I am pretty sure its groundhogs and deer. The one year that I did get fully developed sunflowers the gold finches had a ball hanging upside down to eat the seeds. The petals usually dont all stay on. You put this in a container and put your flower in it covering up the flower and it will dry keeping the petals in place and preserving the color.