Pretty much what Jim said. If I wanted to TRADE seeds, and I wanted to be sure there was no cross pollination from another variety, I would bag the blossom before it opened, so pollinating insects couldn't get to it. The year I attempted to bag blossoms I got NO fruit from the bagged branches. If I was saving just for myself, I probably wouldn't bag.

It's possible to improve (greatly) the purity of saved tomato seed. Here are some suggestions:
1) Plant a number of any given variety (more is better)

2) Group your varieties in clusters instead of rows.

3) Keep some distance between varieties. I generally try for 20' between varieties. Though planting something tall, between varieties, as a barrier crop can enable one to plant them closer together.

4) Keep cherry and currant tomatoes far away from standard varieties. They cross much more readily, as in, they are really good at getting their pollen to other plants. Beefsteak varieties are also a bit more prone to crossing, than are standard varieties. So some more distance is helpful.

If you didn't do any of these things you can still save seed. Then, in the next growing season (or more) rogue out any off types. It is possible to purify crossed seed, as there are almost always some pure plants.

This year's tomato seed, stored at room temperature and with fairly low humidity, should be good for at least four years.

Does it matter when you harvest the tomatoes first ones or later in the summer to save the seeds?? I know this is a dumb ? but wondering!

Thanks

Sorie6, I save seed from tomatoes and peppers, too. I do pretty much what Jim and Amy do, and they seem to always come out fine. Two of my fall tomato varieties are from my own saved seed. Pick a good healthy tomato...you want one with qualities that you want to pass down to its offspring. I don't think it makes any difference when in the summer you pick the tomato as long as it's nice and healthy.

Some people prefer to save from the first tomatoes of the season because they feel those are less likely to be cross-pollinated. I don't know if that really is true. I used to spend a lot of time saving seed, but I don't any more. Life is too short and I have too many other things to do during food preservation season. I had to draw a line somewhere, and finally decided seed saving was the thing I could cut from the To Do list.

Thanks folks. It's just DH and I and I don't do any canning or stuff you folks do. Just grow a few tomatoes and cukes and peppers. DH won't eat many veggies :>( !

I've seen instructions saying to avoid the first fruit. But then, a good friend, and very good at seed saving always saved from the first fruit. I save when I can...

There is a real satisfaction in saving something over time and really getting familiar with it. But usually it does take time and effort.

Old Friends in the Garden