Our mission is to share the wonders of the natural world by publishing books from experts in the fields of gardening, horticulture, and natural history. Grow with us.

Want to save your own tomato seeds? Here’s how.

by Timber Press on October 29, 2013

in Gardening

Photo: Wikimedia

Photo: Wikimedia

Have you grown the perfect tomato plant?

Perhaps you’ve been struggling to grow tomoatoes in a particular spot and this year you finally succeeded, or maybe you’ve been experimenting with different tomato plants for a favorite recipe and now you’ve found one with the right flavor?

You could be on your way to growing your very own heirloom variety. But first, you’re going to want to save those seeds. Here’s how to do it.

Wet processing

This is the [seed saving] method used for tomatoes, cucumbers, squash, and other fruits. Wet processing can be done with or without fermentation.

  • With fermentation: tomatoes and cucumbers; the fermentation process is used to remove the germination-inhibiting sac that surrounds each seed in the fruit
  • Without fermentation: all other vegetable fruits
  • What you’ll need: knife, spoon, glass jars, bucket, sieves, coffee filters

Wet processing with fermentation

Cut the tomato or cucumber in half. With a spoon, scrape the seeds into a glass jar and add a little water (do not use seeds from rotten fruits). Glass jars [Or, as pictured here, petri dishes] are used so that one can see when seeds sink to the bottom. Cover the jar loosely to prevent pressure from building up inside due to fermentation. If this is your first time fermenting seeds, proceed with care and observe the seeds closely. Once the germination-inhibiting layer is gone, the seeds then find themselves in optimal conditions to germinate (warm and moist)—if the seed germinates now, it is essentially ruined. To guard against this, use a simple finger test: when the seeds no longer feel slippery, but rather rough instead (usually after a day or two), that means the gelatinous sac surrounding the seed is gone. Seed sinking to the bottom, with the pulp remaining at the surface, also indicates that the sac has dissolved.


A grayish white layer of mold may develop on the surface. Frequent stirring can prevent a dense layer of mold, which could potentially infect the seeds, from forming on the surface and also encourages consistent fermentation throughout the solution. If there is little pulp in the jar with the seed, add a pinch of sugar (as a replacement for the fructose contained in tomato pulp) to ensure vigorous fermentation and to suppress the formation of mold. Fermentation is not complete until seeds have separated from the pulp. Ideal temperature range for fermentation: 73–86°F (23–30°C).


Add water to the fermented seed-pulp mixture and mix. When the seeds have sunk to the bottom, pour off the pulp and any dead seeds floating at the top. Repeat this process of adding water and pouring off pulp until the water is clear. Clean further under a powerful stream of water in a sieve if needed. This is typically all the cleaning that is needed.


At this point it is important that the seeds be dried as quickly as possible. We place the seed in coffee filters, which quickly wick away moisture. Warning: do not press water out of the seeds, which may cause the seeds to clump together such that they cannot be separated without damaging them. Place up to one teaspoon of seeds in each coffee filter. Seeds can also be dried on a plate. Set out in a warm, but not hot, place (73–86°F [23–30°C]) with good air circulation and label. Seeds should be dry in two days at the most. If needed, seeds can be further cleaned in sieves after drying.


Wet processing without fermentation

In wet processing without fermentation, seed is simply removed from the fruit and then washed in a sieve under running water. This is done with, for example, melon, eggplant, and groundcherry. If the seed does not separate from the fruit by this method, soak the fruit for 12 to 24 hours (keep cool; the point is not to ferment but rather to soften the tissue of the fruit). Dry seed well afterward.


Featuring information on how to maximize seed quality and yield for more than 100 crop plants, and including critical information on pollination, isolation distances, cultivation, harvest, storage, and pests and diseases, The Manual of Seed Saving is an essential reference for all food producers including vegetable growers, market gardeners, and farmers.

Click image to see inside this book:


Being able to save seed is a key to food security and local food production. Thanks to this remarkable book, we can take this essential practice into our own hands. —Steve Gliessman, Professor Emeritus of Agroecology, University of California, Santa Cruz

{ 1 comment… read it below or add one }

1 Seminte February 1, 2018 at 8:55 am

You need to ferment the seeds, because this process will kill any disease organisms that are present. Using this fermentation step when saving tomato seeds will also get rid of the slippery gel that surrounds the seeds. If you don’t get rid of this protective coat, the seeds will have a hard time germinating when you go to plant them.

Leave a Comment

Previous post:

Next post: