“What’s that strange smell?”
“Yuck! What stinks?”
“Oh, no! Mom’s doing tomato seeds again.”
These are comments often heard at our house in August and September. The unusual odor wafting from the kitchen indicates that it’s tomato-seed-saving season.
Most seeds are easy to save. They only need to be cleaned and dried. But saving tomato seeds involves an extra step: fermentation. It may seem complicated at first, but it’s actually quite easy (and not really as disgusting as it sounds).
The first step in saving any kind of seed is to make sure that it comes from an open-pollinated plant. In other words, you can’t save seeds from hybrid vegetables or flowers because their offspring won’t be true to type. Since most of the tomato plants sold at nurseries are hybrids, you’ll have to seek out open-pollinated varieties (also called “heirloom” varieties). All of the seeds sold on this website are open-pollinated.
Even though tomatoes are mostly self-pollinated, the plants that you intend to save seeds from should be isolated by a distance of about six feet from other tomato varieties. This will reduce the chances of accidental cross-pollination. I like to plant other crops like basil, cucumbers, zucchini, or annual flowers between my groups of tomatoes to distract the bees and reduce the risk of cross-pollination.
Choose several fully ripe tomatoes for seed saving. Ideally, the tomatoes should be taken from 3-4 different plants of the same variety in order to maintain the slight genetic diversity found within a single variety.
Slice the tomatoes into quarters, then squeeze out the seeds and juice, or run your thumb along the insides of the pockets of seeds to dislodge them. The seeds and juice will go into a plastic cup, and the leftover tomato flesh can be chopped up for salsa. So there’s no waste.
Label the cup with the name of the variety. I use a piece of paper stuck on with scotch tape. This label can be transferred to the drying plate later in the process. Set the cup on the kitchen countertop or outside in the garage. It typically takes 4-5 days for the seeds to ferment and separate from their gel capsules. This fermentation process not only gives you nice clean seeds, but it also kills any disease-causing microbes that might otherwise infect the next generation of tomato plants. And it improves the germination rate of the seeds.
It’s normal for a harmless, white mold to develop on the surface of the tomato liquid. You’ll know when the seeds are done fermenting when they separate and sink to the bottom of the cup when it's stirred. If you can’t tell, add some water to the cup and stir again. If the seeds are stuck in their gel capsules, they need to ferment longer.
When the fermentation time is up, add water to almost fill the cup. Stir for several seconds, then allow the good seeds to sink (bad seeds will float). Pour off most of the liquid, add more water, and stir again. Continue this process until the seeds are free of all debris. Then pour off all the water, using your fingers to block the seeds from falling out of the cup.
Spread the wet seeds on a paper plate (to absorb moisture) or on a piece of window screen material laid over the top of a regular plate. Spread the seeds around as evenly as possible so they’ll dry out. After the first 24 hours, separate the ones that are stuck together.
Air dry the seeds for 2-3 weeks, or until a seed broken in half with your fingers makes a faint snapping noise. Seeds that bend instead of snap need to be dried longer. Store seeds in an airtight container in a cool, dark, dry place like a basement closet or the refrigerator. Properly stored seed should remain viable for about 5 years.
To me, saving seeds is as much a part of gardening as planting, growing and harvesting. And although my children are not thrilled by the smell of fermenting tomatoes, they can’t help being fascinated by the process of fermentation and the life cycle of plants.