If your not saving seed it does not matter.
If you want to save seeds from heirlooms you separate those alike plants by 20 feet (different sources recommend differt distances) but I think 20 feet will get you 90-95% original plant genotype seed.

Amy,

I think that Pete is right but I would add that bagging Blossums is difficult work and even when you have plants intertwined you don't get more then 1/3 crossing. This means that if you have them a little seperated you're going to have most of your seed being right.

Now if all of your plants are indeterminate, regular leaf with red fruit it can be a problem telling what crossed the following year but if some are determinate and potato leaf ect. it's easy tell the crosses from the pure seed after the seed sprout their first leaves.

I love to find crosses of good varieties. I grow them out in pots and if they have potential I can stablize a new variety and name them after one of my kids :-)

I have found that when you start a mess of seeds of one type togther you will find that several sprouts of the plants seem a little different. This seems to be especially true up until the first several sets of leaves appear but sometimes these differences dissapear as the plants get more mature.

This has worked for me to tell crosses from non-crosses, even in very similar plants. Now if you had a potato leaf plant and some of the sprouts from the seed are regular leaf, it will be obvious that there was a cross. But even subtle differences can be obvious early on.

Greg

I'll be growing different OP varieties within 20 inches of each other, stem-wise...in other words, they will be intertwined. I will bag the blossoms because I want to save seed and have them all be 100% true.

"What I want to know is, since some are hybrids and some are not, can they be planted in the same rows or must they be seperated?"
They can be planted in the same rows. I plant my hybrids and OPs in the same row and I save seeds.

"If they are close together will they some how cross pollinate?"
Close together is a relative term. Most OPs are indeterminate and indeterminates shouldn't be planted close together (as I define close together). But the answer to your question is yes they can cross pollinate. However, unless you're saving seeds that doesn't make a difference. Remember, cross pollination only affects the next year's crop (i.e. the saved seeds), it has no affect on your tomatoes for this year.

"If they do have to be sepearted how far apart?"
For seed purity you don't want to know. :) I've included a link below to Jeff McCormack's write-up. Other opinions and articles can be located with a little searching on the internet.

Good luck.

Randy

p.s. catman - all 529 of you :) - Good luck with that. In the picture below the plants were planted 3 feet apart. So, if you have well grown plants you're going to have quite a jungle on your hands. :) You might want to consider planting dissimilar varieties next to each other. :)

http://i9.photobucket.com/albums/a81/WVTomatoMan/Garden2006/Garden176.jpg

Here is a link that might be useful: Isolation Distances For Tomatoes