Saving seeds from tomatoes is simpler than you think. Once you learn how to save tomato seeds, you can continue growing your favorite heirloom varieties for seasons to come.
If you love eating and growing a certain variety of tomato and you wish to grow the same tomato next gardening season, check whether your tomato is an open-pollinated variety — often called heirloom, especially if it is a much older variety. If it is, the seeds you save will be true to type when grown the following year.
Many of the modern seeds you buy and the tomatoes that you find in the grocery store are hybrid varieties. Saved seeds from hybrid tomatoes will grow new plants and produce fruit, but the fruit won’t be the same as the tomato the seeds came from.
When choosing an individual tomato for seed saving, look for one that is fully mature and free of disease. A tomato that was left on the vine a day or two past peak ripeness is perfect for this.
Cut the tomato in half in any direction you wish. Then, using a spoon or just your fingers, scoop out the gelatinous material containing the seeds. Or, simply apply a gentle squeeze to the cut tomato to release the seeds and surrounding material. (Whatever method you choose, during this step, do not separate the seeds from the gelatinous material.) It’s surprising how easily the seeds come out, though if you are trying to get every last seed, it may take you a few minutes to finish the task.
You’ve kept the seeds and the gelatinous material together because the next step necessary to seed saving success is to let the seeds ferment in their own juice.
There are three reasons why fermenting the seeds is so important.
- removes seed inhibitors that prevent germination
- allows the gelatinous material that causes seeds to stick together to dissolve
- minimizes the risk of tomato diseases surviving on the seeds
Put the seeds, gelatinous material and all, into a container and put the lid on. Place the container someplace relatively cool — about 70°F — and out of direct sun for three to four days.
If saving seeds from more than one variety, prepare multiple containers with labels before you get to work. This is important because once seeds are taken out of the fruit, you won’t be able to tell them apart.
For a container, you can use a simple air-tight plastic jar with a twist-on lid. Label the container with the variety of tomato and the month and year that you saved the seed. Older seed generally has a poorer germination rate than newer seed, so it’s best to always keep track of when seeds were collected to give you an idea of their viability in years to come.
Once your seeds have completed fermenting, it’s time to clean and separate them. When you remove the lid from your fermented tomato seeds, expect to get a whiff of a foul smell. Yes, it’s unpleasant — but it’s also part of the process.
Pour the fermented seeds into a pitcher or similar-sized container, and fill the rest of the way with water, an inch or two shy of the top of the container.
You may notice that some seeds float to the surface. These float because they have air in them and are not viable seeds.
Give the mixture a stir, allow the viable seeds to settle to the bottom, and then carefully begin to pour the water out and down the drain. (This is where a pitcher with a spout helps.) Stop pouring before the viable seeds at the bottom pour out. This first flush will wash away most of the gelatinous material, but you should repeat the process two or three more times.
Once your seeds have been flushed clean, pour them into a fine-mesh strainer and allow the water to drip off.
Next, move the seeds to a napkin or paper towel where they will finish drying. If you have a paper coffee filter — even better. I recommend using paper coffee filters because they don’t break down when they are wet, and they are super easy to work with. And the bonus is their bowl-like shape provides an extra safety measure to keep the seeds contained.
Disperse the seeds evenly on the paper towel or coffee filter, and leave in a well-ventilated space at room temperature for a few days to one week. During this time, continue to separate the seeds a couple of times each day. Running your fingers through the seeds gently will prevent them from sticking together in clumps once dry. You’ll be glad you did this when you are sowing individual seeds next season.
The last step before long-term storage is to move the dry seeds back into their labeled container. I add a silica gel pack or two to each container to remove moisture that can cause seeds to get moldy.
I keep my seeds in a refrigerator, but room temperature is also fine. A cool, dry place is all you need, and your seeds will be good to go for years to come.
Links & Resources
joegardener Online Gardening Academy™: Three popular courses on gardening fundamentals; managing pests, diseases & weeds; and seed starting!
joegardener Online Gardening Academy Master Seed Starting: Everything you need to know to start your own plants from seed — indoors and out.
*Disclosure: Some product links in this guide are affiliate links, which means we would get a commission if you purchase. However, none of the prices of these resources have been increased to compensate us. None of the items included in this list have any bearing on any compensation being an influencing factor on their inclusion here. The selection of all items featured in this post and podcast were based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Rain Bird, Corona Tools, Milorganite, Soil3, Park Seed, and Exmark. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.