Seeds are a mystery. When we look at them, they look dry and lifeless. Some are large compared to others, while some are tiny.
So, how do we know if planted, that they will grow?
If you have an old seed collection from years passed, or one that was handed down to you and aren’t sure if they’re worth planting, a seed germination test is the quickest and easiest way to test for seed viability.
Armed with this knowledge, you can make the decision to plant them or not.
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In order to understand how seeds work, let’s start with the anatomy of a seed.
Inside the seed coat, you will find a cotyledon, plumule, radicle and hilum.
The hilum is the scar left behind from the seed’s former connection to the ovary wall or funiculus. In terms of a bean seed, the hilum scar is a reminder of where the bean seed had been attached to the inside of the bean pod (ovary wall). This location was the junction point where the bean seed received moisture and water from the mother plant. As the bean began to dry, the moisture level coming through this junction decreased over time, eventually ceasing. Once all moisture transference stopped, the bean seed would be completely dry and ready for collecting.
The cotyledon is the seed leaf within the embryo of the seed. After germination, the cotyledon becomes the embryo’s first leaf. The purpose of the cotyledon is to nourish the baby plant within the seed coat. Depending on the amount of nutrition remaining within the cotyledon, germination will either occur or it won’t. The cotyledon determines seed germination. While our seeds lay dormant in storage, the cotyledons within their seed coats feed the embryos (baby plant). Some embryos require more nutrition, thereby consuming the available nutrients within the cotyledon at a faster rate and greatly reducing seed viability over time. This explains why onion, leek and parsnip seeds have a short viability window of 1 to 2 years. Other embryos consume their cotyledon nutrients at a slower rate, thereby keeping the seed viable for many years, ie. tomatoes, peppers and squash.
The radicle of the embryo will eventually turn downwards after planting and set roots in the soil. The plumule will produce the seed’s first true leaf.
How Do We Test Seed Germination to Determine if Our Seeds are Viable?
Perhaps we have seeds that were passed down, that are over 8 years old? Or maybe they were discovered in an 800 year old cave?
For more information on the best date to start your seeds, check out my Seed Starting Calculator. Simply enter your final frost date and all the appropriate dates will be listed.
Rather than planting out all our old seeds, and potentially wasting valuable garden space or experiencing feelings of disappointment and regret, a germination test would be the best way to protect oneself from time lost, lost garden space or any other disappointment.
A germination test is particularly useful when carried out on difficult to germinate seeds. A germination test creates accelerated conditions for seed germination and any difficult to germinate seeds can be tested, then transplanted into a pot once germination occurs.
How to Complete a Seed Germination Test:
- Seeds (at least 10)
- 1 square sheet of paper towel
- Sealed zipper bag or plastic container
- Permanent marker (to mark the starting date)
- Some water
- Select at least 10 seeds to test from one seed package. The more seeds you’re able to test the better, but if you only have a small number of seeds, at least 10 seeds will suffice.
- Wet a sheet of paper towel and squeeze out any excess liquid.
- Lay out the damp paper towel, as flat as possible.
- Space your seeds out on the wet paper towel, at an equidistant spacing.
- Fold the paper towel, being careful not to move the seeds.
- Carefully place the folded paper towel into the plastic zipper bag.
- Mark the date and seed variety on the front of the zipper bag, with a permanent marker.
- Place the zipper bag in a bright spot.
- Wait 3 to 4 days, then check on your seeds. If they haven’t germinated (sprouted), put the paper towel back in the bag and back into position.
- Wait 2 more days, then check the seeds again.
- Once a majority of the seeds have sprouted, count the number germinated and divide that number by the total number of seeds tested.
- Multiply that number by 100 and you will have the percentage (%) of germination.
- Use this number as the average percentage of seed viability for this seed package.
To help understand how this works, here’s an example: I harvested seed from a kale plant that I had growing in my vegetable garden.
A number of years had passed and I wanted to know the seed viability of this package of seeds. I laid out 20 seeds out on a wet paper towel, folded it up and placed it inside a plastic zipper bag. After 4 days I checked the seeds and found that 18 had germinated.
After a simple division equation of 18 divided by 20, I discovered that this seed variety was 90% viable.
Due to this test, I know that 90% of the seeds in this seed package are viable and will sprout.
If I plant the seeds, it will be worth it and they will grow, since they have a 90% germination rate. If the result had been different and only 25% were viable, then I would either have to discard the seeds or plant 4 times the amount of seeds in order to have a similar harvest, as seeds that are 90% viable.
The next time you are unsure if an old seed package is worth planting or not, run a quick and easy Seed Germination Test. The result that you get will help you determine if the seed is worth planting.
In order to help you further with your seed starting, check out my Ultimate Guide to Seed Starting. There, I go over all the necessary steps to find success with your indoor started seeds.
I’ve also created a handy chart, where you may record and keep track of all the seed germination tests that you conduct. This chart will keep your tests organized and help you to compute their viability percentages.
Check out my Video, where I show you my germination test and how it turned out!
Happy Seeding and Gardening!