Gertrude, the link below is from the FAQ's at the top of this first page and I think it's an excellent discussion and should answer most of your questions.

How pure you want your seeds and for what purpose, home use, sharing with others, trading, which I don't do, listing with SSE, are situations only you can decide.

You'll see in the article that saving seeds by distance is not used by many.

Please read the section on when insects do their pollinating, since in some areas they are most active early in the season, in other areas late in the season. I saved seeds only from ripe fruits late in the season since insect activity where lived was early so the earliest of ripe fruits were more apt to have some X pollinated seed..

I can give you another link from SESE ( Southern Explosure Seed Exchange), written by Dr. Jeff McCormack, which is much more detailed on X pollination or you can Google SESE yourself..

So first, decide what you're going to do with the seeds and then either leave them alone, which I do since my crossing rate where I live is only about 5% meaning that of seed saved from 100 varieties about 5 will have some fruits that might be be cross pollinated.

And that's because, as also discussed in the link, most of the time blossoms are pollinated before they ever open up.

Hope that helps,

Carolyn, who also notes there are some other excellent articles in the FAQ section.

Here is a link that might be useful: Cross Pollination

As explained, the crossing is so minimal that most of us don't worry about it. If you want 100% guaranteed pure then just bag some of the blooms and save those seeds as explained in the link Carolyn provided.

Dave