Seed saving is an excellent way to improve the plants in your garden as well as to save money. Pure, heirloom varieties are preserved this way. Always select the best tomatoes in your garden to get the best seed. The best saved seed from this year, planted next year, will give you the best tomatoes next year. The selection process is ongoing, and is the basis for natural plant improvement.
Prepare the Seeds
Slice the tomato in half crosswise, across its equator. The little chambers that contain the seeds will be exposed.
Squeeze out the seeds into a clean jar, along with the gelatinous substance surrounding them. Combine the seeds from several tomatoes of the same variety in one jar.
Label each jar as you go if you are saving more than one variety of tomato seeds. You must keep varieties separated.
Add some water to the jar of seeds. Cover loosely, and set the jars in a warm place, 60 to 75 degrees Fahrenheit.
On the second day you will notice a fungus growing on top of the contents of the jar(s). This is part of a natural fermentation process. The gelatinous substance can prevent germination, and the fungus actually helps remove it from the seeds. The fungus also creates antibiotics that guard against some seed-borne diseases.
On the third day, fill the jar with warm water, allowing it to stir up the seeds and pulp. Let it settle a bit, and pour off anything that floats. Refill the jar with warm water several times and pour off the liquid until you have only clear water and a layer of seeds on the bottom of the jar.
The seeds that sink are the viable seeds. Floating seeds are duds.
Strain the viable seeds through a mesh strainer.
Place the wet seeds on a paper plate or a paper coffee filter. Spread them out into a single layer and allow them to dry in a cool place. The paper wicks moisture away from the seeds, speeding the drying process and preventing mold. Write the tomato variety on the paper plate or filter.
The seeds should be dry in one to two days. Make sure they are completely dry, or they will spoil in storage. Break apart any seeds that are clumped together, and place them into envelopes or small bags, transferring the label information for each variety.