How to Save Seeds From Tomatoes

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by Marjorie Dussaud

Saving heirloom tomato seeds ensures that the precious, delicious tomatoes from yesteryears find themselves growing again in the gardens of the future. Learning how to save seeds from tomatoes is a safeguard against tomorrow’s uncertainty.

Midsummer is here, and, for most gardeners, this means tomato season! Tomatoes are the uncontested queens of the garden and one of the most beloved plants grown across the world. With over 3,000 varieties of heirloom tomatoes documented by experts like Craig LeHoullier, author of the 2019 book “Epic Tomatoes,” tomatoes have a lot to offer the gardening enthusiast. Some might even say that no single gardener can ever hope to grow them all.

But one can certainly try!

Whether they decide to grow a few select varieties of cherished heirlooms year after year or dive into the “tomato craze,” most gardeners find themselves wishing they could save their own tomato seeds at some point or another on their gardening journey. The reasons for wanting to harvest and preserve one’s own seeds are varied, from the difficulty of sourcing some rare heirlooms to the fickleness of the large seed companies that may drop a favorite variety without warning.

Owning one’s own seed supply is a safeguard against uncertainty and a guarantee that the precious, delicious tomatoes from yesteryears find themselves growing again in the gardens of the future.

The Risk of Cross-Pollination

Seed saving starts by selecting plants that display characteristics worthy of preservation for future generations. Gardeners should always save seeds from the plants showing the best traits of their chosen varieties as well as vigor, high yield, and tomato disease resistance. Those can be hard to quantify, and it can be harder still to find plants that display all the desirable characteristics at once, so proceeding by elimination can be a timesaving and sanity-preserving process!

The next step in preserving seed purity is blossom bagging. Considerable controversy exists around the subject of tomato crossbreeding. Tomatoes have perfect, self-pollinating blooms and are fully capable of setting fruits without the presence of a pollinator, but some precautions need to be taken to ensure purity of the seeds when many varieties are grown close together as is often the case for home gardens. According to expert seed saver Suzanne Ashworth in her 2002 renowned book “Seed to Seed,” tomatoes do experience varying levels of crossing. The anatomy of the flower plays a large role in the amount or absence of crossing of a variety. For example, according to Ashworth, all potato leaf varieties have protruding styles, which exposes the receptive female part of the flower to outside pollen. Double blossoms, which are common in large beefsteak types of tomatoes, also have exposed stigmas, making them prone to insect cross-pollination.

To determine the type of bloom of a particular heirloom tomato variety, the gardener should examine a sample of blooms from each plant under a magnifying glass. It should be noted that most available heirlooms of cherry, paste, slicing, and beefsteak tomatoes have retracted styles (apart from the double blossoms on beefsteaks) and should be safe to use for variety preservation.


Harvesting seeds differs from for the table. Most gardeners harvest large beefsteak tomatoes as soon as they blush to protect them from critters and other nuisances, preferring to allow them to ripen in the safety of an indoor location.

This is not an optimal choice when it comes to seed saving. Tomatoes chosen and harvested for the purpose of seed saving should be very ripe, almost past their edible stage. The longer the seeds are allowed to mature on the plant, the more viable seeds will be collected. A single tomato can yield between fifty and three hundred seeds, depending on variety and size; more than enough seeds for the home seed saver to enjoy for future years.

How to Save Seeds From Tomatoes

Each tomato seed is encased in a gelatinous sack that contains chemicals inhibiting germination. This little trick of nature prevents the seeds from sprouting inside the flesh of the tomato. If left to its own devices, the ripe tomato would fall from the plant and rot away during fall and winter, destroying the gel sack and allowing germination in the spring when conditions for growth are optimal.

This process needs to be replicated for home seed saving purposes, and it is quite easy to do using  . Fermentation will remove the gel sack before drying, duplicating the natural process in a short period of time.

The first step is to remove the seeds from the selected fruit or fruits. Cut the tomato in half and press the gel and the seeds into a large glass container. Continue until all the gel and seeds desired have been collected. Next, fill the jar with room temperature water, covering the seeds entirely.

The following step is best done outside in a shady location as it can get quite smelly. Allow the mixture of water, gel, and seeds to ferment in an open container (it may help to cover it with cheesecloth if flies are present). The natural fermentation process will occur over the next few days. Once a layer of gray or white mold has formed over the surface and the seeds have fallen on the bottom, the gel has been digested and the seeds are ready for cleaning and drying.

To clean the seeds, scoop out any plant matter floating at the surface as well as the layer of mold and discard it — or, even better, compost it! Next, pour the water out carefully. Don’t fret about the floating seeds trying to escape; those are lighter than the others because they lack the embryo making the seeds viable. The heavier seeds waiting at the bottom are the ones you want to keep.

Fill the jar again with water, agitate, and pour. Repeat until your seeds are clean. At this point, it may be useful to use a strainer with a fine mesh.


Drying is perhaps the most important part of the entire seed saving process. Simply lay your newly cleaned seeds on a flat surface to dry, away from direct sunlight. Do not make the mistake of laying your seeds on a wet paper towel to dry! The paper will be next to impossible to remove once the seeds have dried out. A ceramic or plastic plate is all it takes, but some people also like to use coffee filters.

Stir the seeds every day, ideally twice a day, to prevent them from clumping together.

The seeds must be completely dry before storage, so allow at least two weeks in a dry environment for drying up. Using a dehydrator on the lowest heat settings to draw the moisture out is also useful, and many seed savers buy one only for this purpose. Do not store your seeds in a sealed container if they are not thoroughly dry. Any moisture present will spoil the seeds.

Seed viability and Shelf Life

Tomato seeds have a famously long shelf life! A span of 4 to 7 years is generally accepted under ideal storage conditions. Simply store your seeds in a cool, dry place, away from light to keep the germination rate up. Alternatively, the seeds can be frozen after drying, further extending the shelf life to a decade or more.

Marjorie Beausoleil – A lifelong gardener and lover of everything plant-related, Marjorie found her true passion lay in preserving and promoting heirloom varieties of flowers, herbs, and vegetables after starting her first vegetable garden as a new mother in 2008. Her company, Ethos Seed Company, operates from her small farm in Connecticut where she grows many of the varieties offered in her store. Her main passions are tomatoes, peppers, beans, and lettuces.

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