In tobacco growing, we bag the flower heads, it is self fertile, so does not need the bees etc. to pollinate it. If you don't bag the flower heads you will get crosses, that might not be what you want. Controlled crosses are one thing, random crosses aren't so good.
And I do believe in diversity, so I bag several flowers of each type of tobacco. It doesn't take but one growing season to have a lifetime supply of tobacco seeds, then you just trade to get other types!
I also trade alot of tobacco seeds for other things, my most recent trade is for.... mushroom mycelium... ha ha... cool huh?
Don't discount the ornamental nicotianas either. A lot of tobacco is too high in nicotine, so the ornamental is used to mellow it out. And they are all beautiful plants.
I was just working on a tomato bed, from last year, which is peas and garlic this year. I piled it high with leaves all winter, and just moved them as I planted it, and worked my way down the bed. Today was finish the bed, install pea supports, and fertilize the bed in general.
I ran smack into a decision... There are volunteer tomato plants up all over that bed, some bigger than what I am raising inside!
I found the tags, that bed was hybrids last year. They sure are healthy looking babies, and the leaves didn't even phase them at all.
So, being the curious type and liking volunteer plants, I just moved them away from the peas and garlic, and put them in the unplanted (by me) part of the bed, and am going to just let them go. Who knows what the seed will revert to. Somewhere, I can't remember where, I read that even the hybrids at the store, are not really hybrids at all and will reproduce true to the plant. So, I guess, I am testing this theory?
I had beefsteak and cherry tomatoes in that bed, could be an interesting cross? Could be one or the other, or it could be a parent to one or the other used to make the hybrid... hmmm?
I didn't intend to grow any nightshade plants in that bed at all. But, seems they had their own idea...
Talk to your plants.... If your plants talk to you... Run!