Funny thing about sunflowers is my cousin farms over 3K acres and they are constantly trying to get rid of them. Seems like a weed and shouldn't be that hard to grow. Of course trying to grow them on purpose may be totally different.
When I plant wheat and it seems like the darned things are everywhere. Sunflowers don't have to be planted. Just plowing a field or dozing a fenceline is plenty. If there is a bare spot on the ground, sunflowers will be growing there in no time.