Don't Throw Away Those Old Seeds!
How to sprout older seeds with success
I read a lot of gardening blogs and see a lot of people throwing away seeds that are only two or three years old. Being a frugal sort I always try to get my old seeds to germinate anyway. I've found one method that works really well, providing ideal conditions for sprouting. This is especially useful when I've forgotten to save fresh seed from some favorite or valuable plant or when something went wrong and I couldn't save it's seeds. With this method I've been able to sprout some seeds that were 10 years old!
Viability of Seeds
Seeds are living entities. They contain everything they need to sprout and grow into new plants. They actually are carrying on life processes even while sitting in their little paper packets on the shelf, although at a very slow rate. Because of this, as they get older, they begin to loose viability, that is, the ability to germinate and grow, until at some point they are just really and truly dead.
The rate at which this happens has many variables, how the seeds are stored and the species of plant are the two main things that affect viability. Some seeds do not live very long at all, a year or two at the most from when they fell from the parent plant. Others may live as long as ten years or even more. Of course every batch of seed is different. Seeds from healthy, well nourished plants, that were properly dried and stored will have the longest shelf life.
Germinating Old Seeds
This year when going through my seeds I realized that I had not saved any new seeds for a couple of tomato varieties and that the seeds I had were quite old. In fact, the Red Currant Tomato seeds were at least ten years old! The Snow White Tomato seeds were only 4-5 years old. I was curious to see if I could get those 10 year old seeds to sprout. Ten years is a really long time for a seed to retain viability, especially when it's been sitting around my living room in a paper packet all that time and not under refrigerated storage!
Seeds need warmth and moisture to germinate. Tomato seeds, especially need to be about 75 degrees Fahrenheit for good germination. So I set up my grow lights and my germination heating pad in the warmest room of the house. My germination mat can only keep the temperature of the soil about 15-20 degrees above the surrounding air temperature and since it was January, my whole house was pretty cool, especially overnight when the wood stove died down.
To help keep the seeds moist and not dry out on the germination mat I used some of those shallow plastic berry boxes that you get raspberries and blueberries in. These had holes in the bottom for drainage, so they wouldn't stay too wet and cause the seeds to rot.
I used plain perlite in the boxes. Perlite is a volcanic rock that is mined and then heated up really hot until it actually pops, kind of like popcorn. Perlite is the little white bits in traditional potting soil. The great thing about perlite is that it can absorb and hold a lot of water while at the same time there are a lot of little air spaces for oxygen. Both of these (water and oxygen) are important in the soil for good root growth. Also, perlite is pretty much sterile and won't harbor fungus or other pathogens that can kill your seedlings. You can buy bags of pure perlite at your nursery or garden center.
I filled the little berry boxes half full of perlite and sprinkled in my seeds, then sprinkled a bit more perlite over the top. I added a label to the top of the box. I set the box in a tray with some water and put the tray on my germination mat. I made sure to keep the perlite moist. I checked every day for green sprouts.
If your local nursery or garden center doesn't carry perlite you can actually buy it through Amazon!
As soon as I noticed green sprouts I turned on the grow lights and a day or two later began to transplant them into soil blocks. Soil blocks are cubes of potting soil, slightly compressed so they don't need a plastic pot. I keep my block maker set up to make a 3/4" cubic hole in the top of the 2" blocks. So I made up a few blocks and transplanted the little seedlings into them. If you are not familiar with soil blocks, I've written a three part article on Making and Using Soil Blocks.
By the way, that advice to wait to move a seedling until it has its 'true' leaves? I ignore it! It is much easier on the seedling to move it when it just has it's seed leaves, it's root system is a lot smaller and easier to handle without breaking too. I mean, check out the root ball on that tiny seedling in the photo! If I had waited much longer, the roots would have been running all over and tangled up with each other. That means they would have been mangled and broken in trying to separate the seedlings during transplanting.
The little seedlings settled right in and began growing in their new soil blocks. In fact they grew so well in just a couple of weeks I had to move them up to 6" pots and when they were about 6 weeks old they moved up to one gallon nursery pots.
Percentage of Germination
I didn't think about it at the time I sowed the seeds, to count how many seeds I put in to sprout. If I had I could figure out the percentage of germination. Taking a wild guess, it was probably about 20% or somewhere in that neighbor hood for the 10 year old seeds and closer to 50% for the fresher ones. But I did end up with over a dozen healthy & happy tomato plants of both varieties, so I'm happy! I'll remember this summer to save some fresh seed, too!
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