You’ve been growing them in your garden for a few years now, and you know there is nothing like a freshly picked homegrown tomato. Have you ever considered saving the seeds to plant in your garden next year?

Here’s why it’s a great idea: You’ll not only save money on seed packets but will gradually improve your favorite varieties—selecting those characteristics that you most cherish. It’s also a guarantee that you’ll be able to keep planting the varieties you prefer, because seed suppliers have a nasty habit of suddenly discontinuing certain varieties. Last but not least, this is a satisfying autumn garden skill to develop. Here’s how…

  • Save seeds only from heirloom (“open-pollinated”) tomatoes. Seeds from hybrids certainly can be saved and grown, but they won’t produce plants that are like the parent plant. That’s because they are the result of crossbreeding, so the plant may more like one of its “parents”—or more like another one. Only plants named “heirloom” yield plants that are true to seed. If you’re not sure whether your tomato plants are heirloom or not, check the original seed packet or ask at the store where you bought the plant. It’s hard to tell by looking, but in general, hybrids tend to be more uniform and perfectly shaped and colored, while heirlooms may be misshapen but often are more colorful and have better flavor. Note: Don’t worry about cross-pollination with other tomato varieties you may be growing—tomato blossoms are almost entirely self-pollinating.
  • Flag the best plants—literally. When you notice that a certain plant or plants has produced especially good-tasting, handsome or large fruits…or ripened at a time you prefer, such as very early or very late in the season…or yielded an especially bountiful harvest…tie a strip of surveyor’s tape or cloth to that plant’s cage or stake.
  • Leave a few of the best tomatoes on the vine. Seeds need to develop completely inside the tomato, so choose only fully ripe tomatoes—those that are deeply colored and neither too firm nor mushy. Tip: Leave several tomatoes on the vine this way so that you get a representative sample from the tomato plant that you’ve selected.
  • Remove the seeds. When the seeds have had time to develop, pick the tomatoes, take them indoors, cut them in half and scrape out the seeds with a spoon or knife. (I use a grapefruit spoon, which has serrated edges.) Don’t worry if tomato pulp sticks to the seeds—the next step will take care of that.
  • Ferment. Put the seeds, pulp and all, in a canning jar or similar jar. Add water about halfway up, and replace the lid. This soaking breaks down the gelatinous membrane around the seeds, which can inhibit germination. It also kills many seed-borne tomato diseases, a nice plus. Viable seeds will sink to the bottom. Everything else will float to the top. It’s OK if a little mold develops—it will smell funky but won’t hurt the seeds on the bottom.
  • Store. Keep the jar in a spot at room temperature until the gelatinous seed casing has broken down—usually about four days—ideally in an out-of-the-way place where nobody will knock it over and the stinky smell won’t be an annoyance…a shelf or cupboard, perhaps. Tip: If you’re saving seeds of more than one variety, remember to keep them straight by labeling each jar.
  • Dry. On the fourth day, remove everything that’s floating and discard it, and scoop out the good seeds into a strainer and rinse them. Then lay them on three stacked sheets of newspaper to dry for a week or two. Tip: For best results, use your fingers to stir the seeds every day to ensure even drying and to prevent the seeds from bunching up. Change the second and third (underneath) sheets every day or two.

How do you know when your seeds are dry enough to store? Simple: They won’t stick to the newspaper anymore. Store them in a small airtight container such as a baby food jar or a small canning jar in a dry, cool place until next year. The ideal temperature is in the 50s, so a shelf in a cool basement is perfect. A garage is another possibility.

Next year, you’ll have the satisfaction of planting seeds you know will produce some of your favorite tomatoes ever—and that joy will only increase with each year.

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