After many years of experiments, I am yet to find a sunflower that doesn't require heavy staking in season. This year I think I touched rock bottom with "Valentin": expensive seeds, low germination rate, needed staking when one and half feet tall already... never again.

I have no problem with size. I plant sunflowers near the vegetable patch just to add some color in late Summer and to cut off the flowers at the end of the season and hang them as wildbird feed. But I have enough problems with plants needing staking already and I am getting old.

Any advice is appreciated.

Try a multi-headed variety instead of one big single. Also, don't fertilize or overwater the singles— either of those cultural practices can cause stalk weakness. They should be able to stand on their own.