How to Save Tomato Seed
Tomatoes originated in Central and South America. When the Spanish brought the tomato back to Europe, it was thought to be poisonous. Many thought you could eat them if they were cooked really well, but even then you should not, and if you ate one raw, you could die right away!
Tomatoes have perfect self-pollinating flowers. Despite that, cross-pollination by insects is possible. The prevalence of cross-pollination is heavily debated amongst gardeners. Some say crossing is common, while others report no crossing after growing different varieties next to each other for many years. In my experience they do tend to cross. I saved seeds from my plum and paste tomatoes from last year, and this year my plants had some characteristics of both varieties. In some instances that might be negative, but my plants have been extremely productive, tasty, and I have had less pest issues. However, if you are looking to preserve a particular variety, you will need to take additional action to ensure seed purity. Caging is an option, but I prefer isolation. You can isolate your tomatoes by keeping different varieties at least 100 feet away from each other.
Steps to save tomato seed
1. Identify your strongest plants, and mark them so you know which tomatoes to save seed from. Make sure to isolate or cage.
2. Take a fully ripe tomato from your previously identified strong plants to save seed from.
3. Cut the tomato in half, down the middle or equator. The stem or bottom should not have been cut. This will expose the seeds.
4. Take a spoon, and spoon out the gelatinous sacks containing all the seeds into a glass.
5. Cover the glass with saran wrap, and poke a couple of tiny holes in the top, and place in a sunny spot.
6. A fungus layer will appear at the top of the glass in a couple of days. This fungus is really important, as it will eat the gelatinous sack that encases your seeds, and it will produce an antibiotic that will prevent certain seed borne diseases.
7. After three to five days, the fungus should have eaten your gelatinous sacks. Add a little warm water and the heavier viable seeds should drop to the bottom of your glass. Simply remove the fungus layer then strain the viable seeds.
8. Put seeds in a single layer on a paper towel in a cool dry place to dry.
9. After seeds are dry, place in an envelope a put them in a cool, dark, dry place. You can tell that the seeds are dry, if you try to bend them and they break.