Testing Garden Seeds for Germination Rate

If you have old seeds and wonder if they will sprout, you can find out by testing garden seeds for germination rate. The same process may be used to presprout seeds that need a head start. For example, older seeds with a coat that has hardened with age may be presprouted to improve moisture penetration.

This spring I had occasion to test seeds of Gusto bell peppers. I have grown Gusto in my garden for many years, saving seeds and starting them each spring in pots under grow lights. This year my seeds didn’t vigorously sprout within the usual 8 to 9 days, so I started a few more. They, too, didn’t sprout.

Germination Test

At this point I was getting extremely concerned, because I have never grown a bell pepper I like as well as Gusto. To find out if I had any viable seeds from past years, I conducted a germination test to find out if my Gusto growing days are over. Here’s the process for testing garden seeds:

1. Dampen a paper towel. Use tweezers to space 50 seeds (or however many you want to test) on half the towel. Fold over the other half of the towel to surround the seeds with moisture. Tuck the towel into an unsealed sandwich bag. Select-a-size towels are just the right size that, when folded fit nicely in a sandwich bag.
2. With a permanent marker, label each bag. In this case I had a batch of Gusto seeds that were collected in 2015 and another in 2014. I labeled the former G-15 and the latter G-14. Pepper seeds are good for 3 to 5 years, after which the germination rate gradually drops off.
3. For sprouting, pepper seeds need a dark place with a temperature of about 70ºF. I could can put them in a cabinet or drawer, but I am afraid I will forget to check them. So I use an old leather-and-velcro pouch from a defunct radio. It’s the perfect size for several sandwich bags. Using the pouch, I can keep the seeds on a countertop as a reminder to check them for sprouting.
4. After about a week, start checking the seeds every 3 to 4 days. By holding each bag up to light, you can see whether or not any seeds are sprouting.

Germination Rate

After 20 days, 8 of the G-15 seeds had sprouted. With the tweezers I transferred them to soil-filled pots. Leaving the sprouted seeds in the wet towel runs the risk that the roots will grow into the towel, then break off when moved.

At that point my Gusto seeds had a pitiful germination rate of 16 percent. I left the rest of the seeds in their bags. To my surprise on day 25, 6 more of the G-15 seeds and 12 of the G-14 seeds sprouted.

By day 30, when I terminated the test, 30 more G-15 and 27 more G-14 sprouted. The total for G-15 was 44 out of 50, or 80 percent. For G-14 to total was 39 out of 50, or 78 percent. As expected, the older seeds took longer to sprout and had a slightly lower germination rate. But both batches sprouted better than the 70 percent rate in the description of the original Gusto seeds I purchased.

And wouldn’t you know it — some of the first seeds I sowed in pots finally did sprout.