Testing the viability of bean seeds.| Photo by Kate Garland
With spring just around the corner, you might be browsing the seed catalogs to order your favorite fruit and vegetable strains. But don’t be so quick to buy new packages—those leftover seeds from past seasons may still be viable for planting. You can test old seeds to find out.
Are your old seeds viable?
The question to ask yourself when planting old seeds is: are they still viable?
- Are your seeds still alive?
- Will they germinate and grow into healthy plants?
How do I test the viability of seeds?
To test if the seeds will germinate, take a paper coffee filter or a wet paper towel. Squeeze it well so it’s moist but not soggy. Place five test seeds on the paper towel and slip them into a plastic bag or sealed container to keep them from drying out.
Viable seeds should germinate in about 6-10 days, but you should check the time frame listed on each seed packet. You can also find rough guidelines through The Old Farmer’s Almanac.
Cold-hardy plants like peas, greens, and cabbage family crops can germinate at lower temperatures, like 55 to 65 degrees F. But tomatoes, cucumbers, squashes, and other heat-loving crops need temperatures closer to 70 F to sprout. Try replicating those temperatures indoors for the seed germination test.
Seeds that need a little more heat can be placed near a lamp or in the kitchen. You can find heat mats that can go under your seed starting trays when you have viable seeds ready to plant.
A quick alternative test if you’re itching to start a tray of seedlings is to drop a few seeds into a glass of water. If they sink, they are good. If they float, throw them. If you have a mix of failed and germinating seeds, you can try them, but plant extras to compensate for the reduced yields.
What science has to say about germinating old seeds
When it comes to germinating old seeds, you need as much control as possible over the growing environment. The last thing you want is fluctuating humidity, light or heat levels.
Before I give an overview of some simple tips you can use to germinate old seeds, I’d like to share a little of the science behind germinating old seeds in case you want to take a deep dive into the science of germination of old seeds.