Three years ago, I planted some sunflowers in the parking strip. I can’t even remember what variety they were, I think they were some dwarf hybrid Mexican type, petite and bronze and cute. The following year, I didn’t get around to planting any but noticed some familiar-looking volunteer seedlings in the same part of the garden so let them stay to see what would happen. They shot up over late spring and early summer to become 6 ft. and taller volunteer sunflowers!
They aren’t really true to type anymore, but that’s fine by me. Now I no longer bother with seeds from a catalog, just let the squirrels and birds have at them in the fall and see what comes up again next year. We can view their happy heads from the house and they seem to attract a lot of attention from neighbors and passers-by, even though they require zero effort to cultivate.