I was so disappointed to come home yesterday afternoon and find one of my sunflowers knocked over by the severe winds :( I knew as soon as I saw it that it was done for. The huge sturdy stem never gave but the roots did, broken just below the grade.
I couldn't even bear to take a picture of it or the two remaining ones after John helped me take it down.
The other two are still fine, but with the winds not dying down that evening I didn't take any chances either. I tied both to the fence behind them to keep them from swaying to far and breaking from their roots. Three ties for each - one directly back to the fence and one about 12-18 inches to either side of the first. I thought that would minimize the sway in most directions and it the was the best I could do. Those monsters are already 8 feet tall and haven't fully developed the main heads yet. I don't have any staking material strong enough to handle them.
Hope that works.