This might not be the difinitive answer, but I had a great crop of sunflower
plants in my deck planters last year that the squirrels had planted. They
got the seeds from the bird feeders. They were 3-5 feet tall and were at
least three different varieties. I now use the "no waste" bird seed, so I'm
going to have to figure out what to do, because I have lousy luck growing
them myself. The squirrels still steal and bury the seeds, but since the
shell has already been removed, I presume they sure won't turn into plants.
And I'll be darned if I can picture in my mind's eye if the sunflower seeds
last year were striped or black oil. If I had to bet, I'd say they planted
the black, because I remember getting a few bags of straight black oil
seeds. The seed MIXES had both kinds.