I have an open pollinated tomatoe that I want to keep seeds from. How far apart from other varieties do I have to plant it to prevent cross pollination? I was told that I can plant it together with any Hybrid and it will not be pollinated by the hybrids. I don't understand how that could be correct, since I'm sure that someone developed these heirloom varieties by crossing different types of tomatoes. Unless hybrid tomatoes don't produce viable pollen? Can someone please explain? I really would like to keep these plants growing true from saved seeds. Also I have neighbors about 150' away that grow various types of tomatoes. Will their plants likely cross with mine?