how long do tomato seeds last
Have you ever found a pack of tomato seeds from a year or two ago and wondered if you could germinate those seeds and get them to grow? If you’ve ever had this happen, the answer is definitely try it!
Yesterday, I uncovered some seeds that I thought were lost to time. One was a tomato I had been breeding myself; another was a commercial packet that contained seeds that did not match the variety. It was from a highly respected seed firm, so the tomatoes were either 1) a mis-labeled pack or 2) crossed seeds. I’ve had crossed seeds before from a commercial pack, and it’s always exciting to see what might grow out.
How old are these seeds? They’ve been patiently waiting for 5 years!
How Long Do Tomato Seeds Last?
I’ve had this happen in the past, and I’ve successfully germinated seeds that I had for 10 years (see a previous post on seed germination) . So, I’m thinking that because the seeds were in a cool, low-humidity location, my 5-year-old seeds should germinate OK.
I don’t expect a 90% rate — probably more like 70 to 75%. But hey, I planted 8 seeds of each of the two packets, so even if I get just one or two good, sturdy plants from each, I will be thrilled. 🙂 (More is better, though, so I can select the healthiest plants to work with.)
Germinating Old Tomato Seeds
Because I want the seeds to have the best possible chance, I got together the following:
- 3-ounce paper cups
- Seed-starting soil
- Liquid kelp, diluted to 1/3 strength
- Windowsill greenhouse
- Seed germination heat pad
- Pair of scissors
- Plant labels
With the scissors, I cut slits in the bottom of the paper cups (for water drainage). I filled them to the top with the seed-starting soil and placed each cup in the windowsill greenhouse. When all the cups were filled, I took my liquid kelp mixture and soaked the soil, letting the water run out the bottom.
I let the cups stand for a few minutes, then lightly pushed the soil down. When I was satisfied that the top of the soil was moist, I put on the soil surface 4 seeds per cup. (Normally I’d only plant 2 per cup.)
I put a layer (maybe 3/8 inch thick) of the seed starting soil on top of the seeds and once again, lightly pressed down.
I added labels to the cups with the name of the tomato, and filled the windowsill greenhouse with enough water to come up 1/8 inch up the sides of the cups. That would provide enough water to make the seed-starting soil moist all the way through the cup, to the top.
Put the top on the greenhouse (to keep the humidity up) and set the whole kit and caboodle on the seed germination heating pad, which would gently warm the bottom of the greenhouse, and by extension, the soil and seeds.
How Long Will it Take?
Good question! Normally it takes anywhere from 3 to 10 days to germinate tomato seeds, with about 5 days being average. Given that these are older seeds, I don’t expect to see signs of germination for 5 days at the earliest, 7 days on average. Therefore, I wait impatiently. 😉
Saving tomato seeds isn’t terribly difficult, although it can get a wee bit on the aromatic side. Here are some tips on how to save tomato seeds.
Know Your Tomato Variety
The first thing is you need to know if the tomato variety you want to save the seeds from is a hybrid or open-pollinated.
A hybrid is a cross between two different tomato varieties. Seeds grown from the hybrid may or may not be like the plant from which they came. (Most likely they will be different.) Don’t save seeds from hybrids unless you want to be surprised!
If your tomato variety is open-pollinated (which includes heirlooms), then the plants you grow from the seeds you save will be just like the parent plant.
Saving Tomato Seeds
Here are the steps for saving tomato seeds.
- Pick the best examples of your ripe tomatoes (choose three or more tomatoes from each variety of the plants).
- Slice the tomatoes in half and squeeze the tomato juice and seeds into a small plastic container. Put only one tomato variety in each cup.
- Add a tablespoon of water.
- Label the container with the name of the tomato variety.
- Cover the cups loosely with plastic wrap and set them in a warm location (between 75 and 80 degrees is best). If it’s warm enough, you may want to set the cups outside because the next step can get, um, aromatic (smelly).
- Let the container set for at least three days; you will see white scum appearing on top of the liquid in the container. This is normal. And a bit strong-smelling. This is the fermentation process.
If the temperature is warm (around 80), let the container sit for another 2 or 3 days after the fermentation starts; if it’s been cooler, you may need 4 or 5 days. Then you’re ready to clean the tomato seeds.
Cleaning and Collecting the Seeds
Here’s how to clean out the containers and get the seeds. (Hint: do this outside if you can.)
- Grab a pail and either a garden hose with a pistol-grip sprayer or several small bottles of water.
- Add some water to the container with the seeds and swish it around some. The good seeds will fall to the bottom; bad seeds will float to the top.
- Dump out as much liquid as you can, along with the bad seeds, then add some more water and swish again. Dump out the excess water.
- Repeat until the water is clear, which means the seeds are clean.
- Grab a paper towel and dump the seeds onto it, to absorb any extra moisture, then transfer to a paper plate.
- Spread the seeds around on the paper plate so they aren’t piled up; they need to air dry. Label the paper plate with the tomato variety name.
- Move around the seeds once a day to make sure all sides are sufficiently dried. They should be good after two or three days, unless you have the paper plate with seeds in a humid location. If that’s the case, give it a few extra days.
- Store the seeds in a paper envelope, small plastic bag or a small container with a lid. Label your container!
Place the seeds in a cool, dry place and they should last several years (although they are best used within 2 to 3 years if possible). However, I have seeds over 10 years old that are germinating fine, even as I write this. Still, the sooner you use (or share) the seeds, the more likely they are to germinate and thrive.
In my previous post about germinating tomato seeds, I mentioned that I had planted quite a few seeds that were at least 10 years old. While I expected some of these seeds to germinate (I do have some rare seeds in my collection), I wasn’t expecting a high germination rate. At most, I was hoping 25%.
Wow, have I ever been surprised! For some of the varieties, the germination rate has been in the neighborhood of 75%. Brandywine is one of them; Yellow Cherry another. Then there are varieties in the 60% range, like Pineapple and White Bush. Of all the varieties I planted, only Big Rainbow has had a low germination rate. Then again, it might be that it’s been slower and more seedlings will start popping their heads above ground today or tomorrow.
I’m trying to decide if the Terracycle I sprayed on the soil on Sunday helped the germination, or at least hastened it. Sunday hadn’t shown much action with the seeds, but Monday a whole bunch showed up. Tuesday a whole lot more. And even today I see some more new seedlings starting through the soil.
The next batch of seeds, I’ll remember to spray the Terracycle sooner (my fault, my plant sprayer had disappeared and I had to go get a new one…and was a bit slow about it). But now I have a new sprayer.
There’s a Problem, Though…
I have a problem now, but it’s a good one to have. I planted way more seeds than I had needed, because I thought the germination rate would be really low. Yikes! I now have way more tomato plants than I have containers, by a large margin. Time to gift my family and friends with some seedlings, or maybe take them to a farmer’s market to sell, in another month or so (after the second transplant).
So, don’t throw out those old seeds without giving them a try, and keep in mind that they may take somewhat longer to germinate than newer seeds. Remember, when germinating, tomato seeds like warmth and humidity.
I’ll give another update next week on how the seedlings are faring.