The Secret to Saving Tomato Seeds: A Simple Guide to Seed Saving & Fermentation

Tomatoes are one of our absolute favourite crops to grow here at Sunnyhill Homestead, and we’re far from alone! They are, and have continued to be our top seller during our annual seedling sale! 

Basket of freshly harvested heirloom and cherry tomatoes in the garden, ready for seed saving.

Whether they’re climbing up trellises, sprawling through garden beds, or ripening in pots on the patio, tomatoes are the star of many summer gardens. 

From that first juicy slicer of the season to sun-warmed cherry tomatoes enjoyed right there in the garden, tomatoes can reward us generously.

If you’re growing tomatoes you love, saving your own seeds is one of the most satisfying (and surprisingly simple) ways to carry that abundance forward into next year, and best of all - for free!! 

Home-saved Black Beauty tomato seeds from the 2023 harvest, stored in a labeled paper envelope for next season’s garden.

With a few tricks like fermenting the seeds, you can improve germination, remove diseases and pathogens, and preserve your best-performing varieties for seasons to come!

Why Save Tomato Seeds?

Saving seeds allows you to:

• Preserve flavour and traits you love (that sweet cherry tomato that never split, or the slicer that thrived in your shady corner).

• Adapt varieties to your specific microclimate (ie/ they will have the genetics to thrive even more in your very own garden!)

• Grow more for free - no need to purchase seeds or seedlings of your favourites each year.

• Share with others - through local swaps, seed libraries, or as gifts.

Yellow tomato blossoms in full bloom, the first step toward homegrown tomatoes and future seed saving.

Unlike some crops, tomatoes are self-pollinating, which means most varieties (heirlooms and open-pollinated types) grow true from seed with minimal risk of cross-pollination. 

*If wanting to be 100% sure there is no cross pollination, you can place a small organza bag over unopened tomato blossoms to prevent pollen from other varieties blowing onto the flowers.

Did you know? At Sunnyhill Homestead, we run a free seed library where Canadian growers can borrow, grow, and return seeds; keeping many seeds including heirloom and open-pollinated varieties thriving in our community and beyond! 

The tomato seeds you save this year could become someone else’s favourite crop next season! 

> Keep reading for details on how to get your own free seeds!

Why Fermentation Matters When Saving Tomato Seeds

If you’ve ever tried to save tomato seeds by rinsing them and drying them right away, you may have noticed they stick together or don’t quite germinate as well the following year. That’s because tomato seeds are surrounded by a natural gel coating called 'locular gel' that contains compounds to inhibit germination. In simple terms, it's nature’s way of making sure the seeds don’t sprout inside the fruit!

Fermentation mimics nature’s way of breaking down that gel. In the wild, a tomato would fall to the ground, rot, and ferment before releasing its seeds into the soil. By recreating that process in a controlled way, we:

• Remove the gel sac that prevents sprouting.

• Increase germination rates significantly.

• Kill off many seed-borne diseases, such as bacterial and fungal pathogens.

• Help the seeds store longer and sprout more reliably when planted.

It might sound complicated, but fermentation is incredibly easy and it makes all the difference!

Step-by-Step: How to Save Tomato Seeds

Ripe cherry tomato sliced in half to scoop out seeds for fermentation and saving.

1. Pick the Best Fruit
   Choose fully ripe tomatoes from the healthiest, most vigorous plants. Avoid any fruit from diseased or stressed plants. The best seeds come from the best fruit, so pick the "best of the best!"

   *You can still seed save from tomatoes that were moderately blushing outdoors and brought inside to finish ripening.

2. Scoop the Seeds
   Slice the tomato and scoop the gel-like seed sacs into a clean glass or jar. 

   

   Scooping ripe tomato seeds and pulp into a jar, the first step in the fermentation process for seed saving.

3. Add Water & Let it Ferment

   Add a little water to the jar (just enough to cover the seeds), and loosely cover to let air in, but keep bugs out. It will attract fruit flies otherwise!

   Let it sit at room temperature in a dark cupboard for 2 to 4 days. I use mason jar seals & rings to cover ours, but I don't screw it on tightly, just enough to keep any bugs away. 

   During this time, natural fermentation breaks down the gel coating. You’ll notice some bubbling and a film on the surface can form - don’t worry, that’s normal!

   

   Tomato seeds fermenting after 3 days, showing natural bubbles and a thin film forming on the surface.

4. Rinse & Strain
   After 2 to 4 days, fill the jar with water, stir or shake gently, and let the seeds settle. Viable seeds will sink, while pulp and floater seeds (which are not viable) will float and can be poured off. Repeat the rinse a few times until the water is mostly clear.

   

   Scooping fermented tomato seeds onto a labeled parchment sheet to dry before storing for next season’s planting.

5. Dry Thoroughly
   Pour the clean seeds onto a labeled plate, parchment paper, or coffee filter. Spread them out in a thin layer and let them dry completely in a warm, well-ventilated area for about a week. Stir daily to prevent clumping or mould.

6. Store
   Once dry, store your seeds in a paper envelope, small jar, or seed packet. Label with the variety and year. Keep them in a cool, dark, dry place—like a cupboard or seed box.

   

   Organizing and placing dried tomato seeds into labeled envelopes for storage in our seed apothecary.

   A Few Extra Tips:

• Fermentation isn’t necessary for every seed, but for tomatoes, it makes a big difference in germination rates and disease prevention.

• Don’t use mouldy, diseased or rotting tomatoes. Select tomatoes that are at peak ripeness and free from disease.

• If you seed save from hybrid varieties, the seeds may not grow true to the parent plant.

A Small Effort, Big Rewards:

Saving your own tomato seeds is one of those small joys that connects you more deeply with your garden and your food. It doesn’t take long, and soon you’ll be rewarded year after year with the best-tasting, best-performing and 100% free tomatoes for your garden!

Once you start, you may never go back to store-bought seeds again!

Holding a handful of large, ripe red cherry tomatoes! Homegrown and ready to enjoy or seed save from.

Have questions about saving tomato seeds or want to share some of yours?

Drop a comment below or check out our Sunnyhill Homestead Seed Library to connect with local growers and share in the joy of seed saving!

Until next time, 

Sarah & The Sunnyhill Homestead Family