Can I Save Tomato Seeds? How to Harvest Seeds in September for Free Plants Next Year

If you’re growing heirloom tomatoes this summer, then it’s a simple September garden job to save tomato seeds so you can grow free plants next year. What’s more, harvest tomato seeds and you won’t only save money but create plants that are perfectly suited to the growing conditions in your garden or greenhouse. Save your own tomato seeds every year and you will create stronger, happier, healthier plants. And you know what that means: you'll grow even more tasty tomatoes, year after year!

One average-sized tomato typically carries a hundred or more seeds, so you don’t need to sacrifice much of your precious crop. Strong tomato seed – and this method magically separates the strongest seeds to harvest – remains viable for five years, too.

You can only save seeds from heirloom or open-pollinated tomato varieties (those that are pollinated naturally by bees) but this encompasses most of the tomatoes we all love to grow at home from Brandywine beefsteaks and San Marzano plum tomatoes to smoky heirloom Black Cherry and tangy Green Zebra. Don’t bother saving seed from F1 hybrid tomato varieties as it won't produce the same plant.

Here’s how to save tomato seeds and store them safely to enjoy free plants and abundant harvests next year.

1. Pick a Perfect Tomato

Select your strongest, most productive tomato plant, and pick the very best tomato you can find that’s fully mature and slightly overripe.

2. Extract the Seeds

Slice the tomato in half then scoop out the seeds and their jelly-like pulp into a glass jar. With smaller tomatoes, you can simply squeeze the seeds straight into a clean glass jar. Label each jar if you’re saving a few different tomato varieties.

3. Soak the Seed

Next you’re going to soak the seed. Fermenting tomato seeds in this way separates the seed from the pulp, which is vital as this gel inhibits germination. Pour water into the jar, aiming for a 1:1 ratio so there’s a roughly equal volume of tomato seeds and water. Lay a square of paper towel over the opening and secure with a rubber band around the jar rim to keep out flies without obstructing airflow.

Now wait a few days for the mix to ferment and the gel to break down. Keep the jar out of direct sunlight but in a warm spot where you’ll see it, because you need to remember to agitate the mix by giving it a gentle swirl every day. A kitchen countertop next to the kettle is perfect!

4. Separate the Seed from the Pulp

The mix is ready when, looking at the jar from the side, you can see it has started to separate with the pulp floating to the top and some seeds sunk to the bottom. This typically takes 4-5 days. A layer of mold or scum may also form across the surface when fermenting tomato seed, and that’s nothing to worry about. Pour in more water and, as the seeds settle, those that sink to the bottom are the heavy, viable seeds you want to keep. Those that float to the surface along with any scum or mold should be discarded.

Slowly tip the jar so the pulp and scum layer runs out but the viable seeds remain in the jar, or use a spoon to scoop that top goop out. Repeat the process of adding water to the jar, letting the heavy seeds settle and pouring off the top layer, to clean the remaining seeds. For a final rinse, tip the seeds into a fine-mesh sieve and hold under running cold water, rubbing seeds with the back of a wooden spoon to remove any last bits of gel if needs be.

5. Dry the Cleaned Seed

Tip the seed onto paper towel and pat dry, then put on a non-stick surface such as a glass chopping board or a glazed plate. Leave them to dry for 2 weeks out of direct sunlight but in a warm spot with good airflow, gently separating any clumps after a couple of days.

6. Store Seeds Safely

Once seeds are fully dry, put them in a paper envelope and store in a dark, cool, dry spot. A tin in a frost-free garage is ideal, and adding a sachet of silica gel to your seed tin will hoover up any damp and prevent seeds molding. If you're a keen tomato grower and saving seed from lots of different varieties, a seed storage box with separate compartments like this 64-Slot Seed Organizer Box from Walmart makes it easy to sort seed, and it effectively blocks moisture to retain 98% seed viability.

Easy! And now you have a store of tomato seed that you know is well suited to the exact growing conditions in your garden or greenhouse, for a bigger, better crop next summer. Keep growing tomatoes and harvesting and storing seed for a few years and, especially if you have the room to grow a few plants, you can evolve the variety to suit your tastes too. You’ll find one plant produces particularly tasty tomatoes, grows extra-long trusses of fruit, or brings a heavy harvest in a relatively compact space, and by selecting those seeds you can bring that beneficial trait to the fore. And then you have the exact right tomato to grow in your garden space and you’re not just growing heirloom tomatoes but your very own heirloom tomatoes.

You'll no doubt save far too many seeds, but tomato seeds make great little gifts. Write growing instructions on the envelope, pop it in a terracotta pot along with a couple of coco coir soil pellets such as these from Amazon and tie with a ribbon to give to family and friends at Christmas.

Can I Save Seed from Shop-Bought Tomatoes?

Most tomatoes sold in grocery stores are produced from F1 hybrid tomato varieties, so it's not worth saving the seed. Grow your own heirloom tomatoes from seed next year, then save the seed from the harvested fruit. A great place to start your journey is with Burpee's Rainbow Blend of heirloom tomato seedswhich has a colorful mix of six varieties including yellow 'Golden Sunburst', orange 'Djena Lees Golden Girl', red 'Bonny Best, pink 'Brandywine Pink', purple 'Black Krim' and green 'Evergreen'.