Tomato pollination question
I have an heirloom tomato that a freind gave me. I am concerned that if it gets crossed with another variety I will not be able to grow it again next year.
I was told that if I only grow it by itself that it will always have seeds that will be true to the variety, and that seems to make sense. I was also told that I could grow it and hybrid tomato varieties in my garden together, because the pollen from the hybrids will not pollinate an heirloom. That does not make sense to me. Can anyone explain this to me? I just don't know that much about tomato genetics. Also how far from another variety will the heirloom need to be to prevent cross poolination?