Testing Seed Germination Rates

If you have seed saved from prior years, it is a good idea to test the germination rate before planting your whole garden with it. Depending on the rate of germination, you can decide if you want to plant normally, plant more thickly, plant single sprouts, or just toss the seed out and start with fresh seed.

Testing seed germination also just happens to be a requirement for the Boy Scouts’ Gardening merit badge, so my son got to do this project for us this year while I took pictures. Here’s how we do it.

1. Gather the seed you want to test. Just for fun, I gave him some cucumber seed I had left from the survival seed can packed for planting in 2000. That’s 12 year old cucumber seed.

2. Count out seeds in a number that is easy to convert to 100. 10, 20, 50, or 100 all work well. The merit badge requirement said to test 100 seeds, so that’s what he counted out.

3. Wet a couple of paper towels, double them over so you have one paper towel worth of space, and lay the seeds on half of that paper towel. The size of paper towel you need will be determined by how many seeds you are testing as well as the size of the seeds. You could also do this with fabric, a kitchen towel, etc. If you are testing large seeds like bean or corn, soak them in a bowl of water overnight first to get them a head start.

I was really surprised at the neat and tidy rows here. This is the same son that leaves socks everywhere he goes and whose room you can’t walk into without stepping on clothes, legos, or books. As expected, the neatness didn’t last and by the end he was just sprinkling the seeds on randomly.

4. Once you have all your seeds on the paper towel, fold it over so the seeds are sandwiched by wet paper towel.

5. Put your paper towel seed package in a plastic bag, make sure the bag has air in it and tie it shut. You are creating a little greenhouse for your seeds.

6. Wait. Some seeds will sprout within a couple of days, others take a week or more. It’s okay to check in on them periodically. When your seeds have sprouted, count up the sprouted seeds. If you tested 100 seeds, this total is your germination rate. If you tested 10, multiply it by 10 to get your rate. If you tested 20, multiply by 5, etc.

We had exactly 11 seeds sprout which equals 11% germination.


In the average gardener’s book, 90-100% can be planted normally, 50-80% can be planted more thickly, and anything under 50% (like 11%) would equate to throwing the seeds out and starting over with new seed. However, if these were the only seeds you had or if you don’t like tossing out possible plants, you can plant the seeds that sprouted and at least you’d have 11 cucumber plants. Kind of slim if you were hoping for 100, but definitely better than none.

Good thing I didn’t plant my whole cucumber patch with these seeds!

This method can also be used for jump starting seeds. A friend of ours starts all her squash this way and only plants the squash seeds that sprout. She doesn’t have any empty spots in her garden and her squash plants are about a week ahead of everyone else’s since she starts them indoors about a week before the safe date to plant outside.