How to save tomato seeds

Wondering how to save tomato seeds? While these delicious veggies seem a bit tricky for seed saving, they are actually pretty foolproof.

Tomato seeds are saved by choosing the tastiest tomatoes from at least six healthy plants. Wait until the tomatoes are ripe before slicing the fruit. Then scoop the seeds and pulp out of the seed cavities and place the wet seeds into a jar. Add a splash of water and a little pinch of sugar if you like.

Place the jar on the counter and stir a few times per day for 1-3 days until the gelatinous coating has dissolved and the seeds don’t feel slippery. Then wash the seeds in a fine-mesh sieve under clean water and place them out to dry for a day or two before packaging them for storage.

Read on to learn all about how to save tomato seeds!

how to save tomato seeds
‘Brandywine’ tomato seeds

Introduction to saving tomato seeds

Tomato seeds are one of the most commonly collected type of seeds. Some of the best-tasting tomatoes are open-pollinated varieties that are perfect for annual seed-saving as they grow “true to type”. This includes favorites like Brandywine, black cherry, and green zebra.

Tomato seeds are harvested and prepared for storage using wet process fermentation. Fermenting tomato seeds removes the gelatinous coating around each tomato seed, or other types seeds with gelatinous coatings (like cucumber seeds).

The gelatinous sack around the seed keeps the seed from germinating too early inside the fruit in nature, but it can inhibit germination altogether sometimes. For this reason, seed savers dissolve the coating off of the seed with the wet fermentation process prior to drying and storing the seeds.

Planting tomatoes for seed saving

To start, you’ll need to grow some delicious tomatoes! Begin by planting at least six plants of your desired type of open-pollinated tomatoes. If possible, 12 or more plants are best for preserving genetic diversity. This will help ensure that you have a good variety of seeds to work with.

Choose an open-pollinated variety

Check that you have chosen an open-pollinated variety of tomato. These can be heirloom or non-heirloom (newer) varieties, as long as they are not hybrids (F1 crosses). Seeds saved from hybrid tomatoes like sungold, Burpee’s big boy, and celebrity won’t breed true to the parent plant. Here are some great open-pollinated tomato varieties:

Isolation between varieties

The group of 6-12+ tomatoes needs to be isolated from other types of tomato plants. The variety you’re saving can be isolated from others simply by planting them far away from other varieties (or only planting one variety) or by putting a physical barrier between varieties.

Isolation by distance is the easiest method for small-scale home seed saving. The minimum isolation distance for most tomato varieties is about 10 feet (3 meters). That said, some heirloom varieties have long styles inside the flowers (longer than the stamens) and may be more prone to natural cross-pollination. An isolation distance of 30 feet (10 meters) is recommended for these more-susceptible cultivars. For commercial seed production, it is not uncommon for producers to isolate varieties by 100 feet (30 meters) or more.

Isolation with a physical barrier is usually done with row cover. The tomato plants can be grown in polytunnels, greenhouses, or hoops covered with insect netting. Be sure to affix the insect netting tightly to the ground and around the edges to prevent bumblebees, mason bees, flies, and other pollinators from entering.

Companion planting for seed saving

Also, take time to plant lots of flowers around the garden area. These flowers are to distract pollinating insects and keep them busy. We want the bumblebees going to nearby flowers instead of potentially crossing nectar between tomato varieties. Cross-pollination of one variety with another can certainly still occur, but the beneficial pollinators usually prefer native flowers instead of tomato blossoms.

Consider planting a tall hedge-like crop like corn between varieties, or a flowering crop like squash. Try to plant crops and companion plants for tomatoes that flower at different times in the summer to distract the pollinating insects.

growing open pollinated tomatoes for seed saving

Growing tomatoes for seed saving

Keep your newly-planted tomato plants healthy by providing consistent water, removing any diseased leaves, and providing a tomato stake and/or tomato cage. You’ll also want to add some slow-release organic fertilizer and mulch the surface of the soil to retain moisture and keep the roots cool.

As the tomato plants start to flower, take a bit of time every day to tap the flower clusters or gently jostle the whole plant. Each tomato flower is self-fertile and has both male and female parts. Jostling the plant can help pollinate the plant by causing the pollen to fall from anthers onto the stigmas of the blossom. Wind can also make this happen all on its own.

Choosing tomatoes to save seeds from

Watch for the first clusters of tomatoes to ripen on each plant. You’ll want to pick a few of these first-ripening tomatoes from each plant. If you have more than 6-12+ plants, consider only harvesting from the plants in the middle of the patch to lessen the chance of cross-pollinated seeds.

Look for vigorous plants that flowered early in the growing season for saving your own tomato seeds. Avoid harvesting tomatoes from sick, diseased, or weak plants in the vegetable garden. Try to choose healthy uniform plants that have lots of flowers/fruit for saving your own seeds.

Harvesting tomatoes for seed saving

The tomatoes should be ripe when harvested. Most varieties are a red shade when ripe, but there are many that are different shades (purple, yellow, et cetera) when perfectly ripe. They should still be a bit firm but should have a bit of give when squeezed.

Try to pick the ripe fruit from within the center of the plant (rather than hanging out the side of the cage, where the flowers were likely more susceptible to cross-pollination). If frost is on the way, the tomatoes can be ripened off the vine indoors on a windowsill. Don’t save seeds from rotten tomatoes.

How to save tomato seeds

The process for saving tomato seeds is pretty simple. Start by slicing into the fruit and tasting the tomato itself. Choose the tastiest tomatoes from each plant for seed-saving. Don’t harvest tomato seeds from moldy or rotten tomatoes.

You’ll need:

  • Knife
  • Glass jar
  • Spoon
  • Elastic band
  • Cloth, paper towel, coffee filter, or window screen
  • Fine-mesh kitchen sieve
  • Plate

Harvesting tomato seeds

Scoop the seeds and their pulpy coatings into a glass canning jar (or cup or bowl). Smaller tomatoes can simply be mashed up if desired.

Add some water to the bowl and mix the tomato pulp and seeds around gently with your fingers. If there’s not much tomato pulp in the jar, add a pinch of sugar to help with fermentation.

Mix gently again and cover using an elastic with a cloth, paper towel, paper plate, or coffee filter.

Fermentation method

Set the jar of wet seeds on the counter. Fermentation will occur naturally and start to dissolve the gelatinous layer from around the seeds.

Stir the seeds a few times a day to prevent a thick layer of mold from growing on top of the seeds. Each time you stir, pull out a few seeds and see if they still feel slippery (meaning there is some gel remaining).

Dissolving the layer completely usually takes 1-3 days. The rough edges of the seeds can be felt when the gel layer has dissolved.

Cleaning the seeds

Once the tomato gel coating has dissolved, the seeds must be separated out from the pulp in the jar. Add some more fresh water to the jar and swirl it around. The viable tomato seeds will sink to the bottom of the bowl while the pulp and other matter will float to the top.

Pour off as much water as possible while keeping the seeds in the jar. Repeat this process until the water runs clear. Then pour the seeds into a fine-mesh strainer or kitchen sieve and spray fresh clean water over them.

Drying tomato seeds

Now the seeds need to be gently dried, promptly. You can let the excess water drain out from the seeds while they are in the sieve, and then place the seeds in small groups to dry on a plate, paper towel, window screen, or coffee filter.

Place the seeds in a warm spot with excellent air circulation to dry. A minimum air temperature of 70°F (21°C) will help them dry quickly, but you’ll want to avoid baking the seeds in truly hot conditions. Tomato seeds usually take only a day or two to dry.

Storing tomato seeds

Once your seeds are completely dry, store them in a cool dry place in a labeled envelope, baggie, or airtight container for seed storage. Be sure to label the container with the name of the tomato variety and the date saved.

Tomato seeds have a long seed life and can last for over five years when properly stored. But if you have any doubts about their viability, it’s always best to test their germination (or start with fresh seeds).

Happy seed saving!

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