You can’t tell, but my friend’s two-story house is hidden behind this forest of sunflowers. Sunflower varieties cross quite easily. While the type she grows are not a species with a particular name, they are likely a cross between our local indigenous sunflowers and some cultivated varieties.
The seeds are too small to be worth the effort for humans to eat, but they feed the wild birds. At the end of the season when they start drying out and falling down, her chickens will make some nice meals out of them.
The birds will miss enough seeds to leave some that will grow back the following year.
I’ve always heard that sunflowers are great for pulling toxins out of contaminated soil, not that this is needed at my friend’s place. An added benefit of the large sunflower curtain is that it shades the house during our scorching-hot summers.