Heirloom vegetable gardeners will find harvesting pepper seeds simple. Pepper seeds strip from the fruit easily and carry little of the pulp that makes storing some seeds messy and tricky. According to Clemson University Extension, properly processed and stored pepper seeds remain viable for at least three years. After longer storage periods germination rates drop and plant vigor declines. Not every pepper plant yields useful seed. Only standard varieties--commonly called heirlooms--breed true. Seed from hybrid peppers produces inferior plants.
Harvest peppers when the fruit changes from immature green to the variety's mature color. Most peppers turn red when mature but some shift to yellow, orange or even almost black. Leave peppers on the plant longer if there's any doubt, since over-ripening won't harm the seed.
Split a pepper in half lengthwise with the knife. Strip seeds from the fruit with gloved fingertips and spread the seeds on a paper towel.
Set the paper towel in the darkest part of a warm, dry room for one week. Don't set the drying seeds in direct sunlight.
Test a seed for dryness by pressing it against one fingertip with a fingernail. Pulpy seeds still hold moisture. Leathery tough seeds have already shed most of the excess water.
Place dry pepper seeds in an open paper envelope marked with the variety name and harvest date. Place the open seed packet in a canning jar along with one packet of indicating silica gel. This type of silica gel changes color when saturated with moisture. Seal the jar tightly and store in a dark place at room temperature.
Check the jar in six hours to see if the silica gel packet changes color. If the blue packet changes to pink in that short time, set the seeds out on a paper towel again and dry for three more days. Repeat the test.
Switch the silica gel packet out for a fresh one if the color change occurs from one to three days after sealing the jar. When the gel packet stays the original light blue color for seven days, the seeds meet the dryness standard for storage.
Keep the sealed jar in a cool, dry location for long-term preservation. Refrigeration increases the storage lifetime of the seeds.