Don't be. Yes they can cross pollinate, but according to the expert Dr Carolyn Male, there is only about a 5% chance of this happening naturally. She has grown thousands of varieties over decades.
Even if you do get a natural cross, it would not show up
in this years tomato crop, rather in the seeds of the next year's generation. This is how all the new varieties come about though, either through natural or intentional crossing.
To be absolute that your varieties don't cross, you can alway “bag” the blossoms. Blossom bags(i’ve never used them)are extremely fine mesh little sacks, that get placed over and blossom and tied. Once the tomato set forms, the bag is removed. This will ensure no outside pollen interaction.
However, blossom bags are a little expensive, hard to find and tedious to work with.
I've grown about 40 different varieties of OP tomatoes in the last five years, all in close proximity, and so far I've have no crosses that i know of.
JJ61
Check out tomatoville.com
JJ61, Thanks for the information! I will be trying some heirlooms next season!
Do you have a good source for these? I have some rare peppers I would like to try those on...