Now is the time to start thinking about your vegetable garden. The seed catalogs have been gracing your mailbox and you’ve had a chance to see all the colorful varieties of fruits and vegetables that are competing with each other for your attention and your dollars. But wait! You’ve forgotten something. What about all those seeds left over from last year or earlier that have just been setting around your house doing nothing. Maybe there’s still life in them?
Whether or not those old seeds are still viable will depend on the seed and just how long they’ve been hanging around, unplanted, on your shelf. Seeds are not a forever thing. Sooner or later they all lose viability and become nothing but dead specks of what might have been. Some seeds can be stored for several years and will still be viable. Others will fail to germinate if not planted after a year.
Research on various types of seeds has given us some guidelines as to how long a shelf life different seeds possess. The website of Johnny’s Selected Seeds has a table that lists different sees and how long you can hang onto them before they lose viability. Here is a link to that table –
Another way to check the viability of your old seeds is to run a germination test. The following information come from North Carolina State University Extension.
Seed Viability Test
What You Will Need
Ten seeds of each type being tested
Sealable plastic bags
A permanent marker
Moisten a sheet of paper towel. It shouldn’t be dripping wet, just uniformly damp. If your paper towel falls apart when it gets wet, use 2 sheets, one on top of the other.
- Place the 10 seeds in a row along the damp towel.
- Roll or fold the paper towel around the seeds.
- Place the paper towel into the plastic bag and seal it. Write the date on the plastic bag, so there’s no guess work involved. If you are testing more than one type of seed, also label the bag with the seed type and variety.
- Place the plastic bag somewhere warm, about 70 degrees F. A sunny window sill or on top of the refrigerator should work.
- Check daily, to be sure the paper towel does not dry out. It shouldn’t because it is seal, but if it get very warm, you may need to re-moisten the towel with a spray bottle.
- After about 7 days, start checking for germination by unrolling the paper towel. You may even be able to see sprouting through the rolled towel. Very often the roots will grow right through it.
- Check your seed packet for average germination times for your particular seed, but generally 7 – 10 days should be enough time for the test.
- After 10 days, unroll the paper towel and count how many seeds have sprouted. This will give you the percentage germination you can expect from the remaining seeds in the packet. If only 3 sprouted, it is a 30% germination rate. Seven would be a 70% germination rate. Nine would be a 90% germination rate, and so on.
Realistically, if less than 70% of your test seed germinated you would be better off starting with fresh seed. If 70 – 90% germinated, the seed should be fine to use, but you should sow it a little thicker than you normally would. If 100% germinated – lucky you, your seed is viable and you’re ready to plant.
You don’t have to waste the seeds that germinated. They can be planted. Don’t let them dry out and handle them very carefully, so that you don’t break the roots or growing tip. It’s often easiest to just cut the paper towel between seeds and plant the seed, towel and all. If the root has grown through the towel, it is almost impossible to separate them without breaking the root. The paper towel will rot quickly enough and in the meantime, it will help hold water near the roots.
Source: North Carolina State County Extension Service — https://richmond.ces.ncsu.edu/wp-content/uploads/2015/01/SeedViabilityTest.pdf?fwd=no