If you wish to skip seed packets altogether and harvest your own tomatoes, the first step is obtaining the fruits. Obviously, they can either be grown from a purchased plant or bought at a local grocery store or farmer's market. Then, follow a few surprisingly simple steps to harvest, dry and store their seeds.
Step 1: Ripe, Red and Ready
The seeds are ready to be harvested once your tomatoes are completely ripe. You can even speed up the ripening process if you want. Just take your green tomatoes and store them in a cool area, wrapped individually in newspaper, brown paper sacks or tissue paper. This keeps one rotten tomato from affecting the whole bunch. Then check on them every day or two to monitor the ripening process.
Step 2: Are you ready for this jelly?
Once they're ripe and red, carefully remove the seeds and the jelly like substance in which they're contained. To properly accomplish this, cut the fruit vertically down the center. Carefully squeeze the substance from the tomato and save the rest to be eaten. No sense wasting a good tomato, right?
Step 3: Storing the Seeds
Next, you'll need to put the jelly and seed mixture in a jar or glass and cover it loosely -- not in an airtight container! The containers should then be stored in an area that reliably remains around 65 to 70 degrees Fahrenheit. Keep them there for three days, taking care to stir each container once a day.
Step 4: Rinse and Repeat
Once three days have passed, fill each jar with warm water. Allow everything to settle back to the bottom. Viable planting seeds will be heavier than the others and stay submerged, whereas extra pulp and unusable seeds will float to the top. Carefully pour out this leftover gunk, along with the water, until all you have left is clear water and those lovely, viable seeds.
Step 5: Strain and Dry
Pour the remaining mixture into a fine strainer and then put the seeds onto a dry paper towel in a safe place where they won't be disturbed. Allow the seeds a couple of days to dry completely and place them in a seed packet or plastic baggie, taking care to break up any clumps that may have formed. Store the seeds in a cool, dry place until it's time for them to meet Mother Earth.