How to Test Old Seeds for Germination
If you're an avid gardener or a homesteader, you may find yourself with a stash of old seeds. Whether they are heirloom seeds passed down through generations or leftover packets from previous planting seasons, you might wonder if these seeds are still viable. Don't despair! With a simple germination test, you can determine whether your old seeds have the potential to sprout and grow into healthy plants. In this post, I'll show you how to test old seeds for germination! At the end of this post, I show the germination rates of all the old tomato seeds I tested!
In our shorter growing climate, (approximately 149 days) I need to start tomato and pepper seeds around 4-8 weeks before our last frost. We're in zone 5b here in Michigan and our average last frost date is May 15th, though I've found over the years that we are having frosts later and later into the spring. I usually look at the extended forecast on May 15th to see if the weather looks safe for the next week or so. For the past few years, we've been planting around the last week in May because of late frosts. To find your planting zone and first and last frost dates, visit the Old Farmer's Almanac and enter your zip code.
For us, that means I need to start tomato and pepper seeds around the third week in March. I have a terrible habit of getting impulsive when the farm stores start to get their seeds in for spring. I want to buy everything and of course, I forget what I already have at home. For years I've been saving packets of old seeds in my seed container. This year I went through my stash of tomatoes and almost threw some of the oldest ones away. But I was more disciplined this year and decided to test my old seeds before buying new ones. And I was pleasantly surprised! Kinda shocked actually!
Let's dive into the process!
To conduct a germination test, you'll need a few basic supplies:
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- Old seeds you wish to test
- Paper towels or coffee filters
- Sealable plastic bags
- A marker or label to identify the seeds
- spray bottle or a way to dampen the paper towels
If you're ready to plant your seeds you can pre-germinate them in paper towels then take the sprouted seedlings and transfer them to potting soil. If you're just checking for viability but are not ready to plant, you can take a sampling of seeds to test the percentage of germination.
1. Sort and Label the Seeds
Separate your seeds by type or variety and label each group. This organization will help you keep track of the results and make it easier to identify any potential issues or variations. I used zip-seal sandwich bags and wrote the seed variety and the date on the bag with a Sharpie. I also should have recorded the package date on the bag. You can find this information on the back of the seed packet. It's usually stamped on the bottom flap.
2. Create a Moist Environment
Moisten a paper towel or coffee filter with water and squeeze out any excess moisture. I sprayed the towel with a spray bottle filled with water. Then I sprinkled the seeds on one half of the towel or filter, leaving some space between them to observe growth. Then I folded the paper towel in half and sprayed again. I folded it once more to make a square.
3. Place the seeds in the bags
Place the square of folded paper towels in the plastic bag. Seal the zipper on the bag halfway to allow air circulation and prevent mold. Carefully transfer the folded paper towel or filter with the seeds into a sealable plastic bag. I used a different bag for each variety.
4. Provide Optimal Conditions
Different seeds have different germination requirements, such as temperature and light preferences. Research the specific needs of the seeds you're testing and try to provide the best conditions. In general, keeping the bags in a warm (not hot) and dark location should work for most seeds. I kept ours in our back bathroom where we were brooding our baby chicks. It was nice and warm in there because of the heat lamp.
5. Check your seed's progress
Check on the seeds regularly to monitor their progress. Depending on the type of seed, germination can occur within days or take several weeks. Most of the tomato seeds germinated after 10 days. Once you notice sprouting, note down the germination rate and the overall health of the seedlings. A high germination rate indicates that most of the seeds are viable, while a lower rate may require adjusting your planting strategy or acquiring fresh seeds.
6. Determine Viability
After a sufficient period, usually 2-4 weeks, you can assess the viability of your old seeds based on the germination results. If the majority of seeds have sprouted, you can confidently use the remaining seeds for planting. If the germination rate is low, you may choose to discard them or plant them in larger quantities to compensate for potential failures.
7. Storage and Future Considerations
If your old seeds have proven their viability, ensure proper storage conditions to maintain their quality. Keep them in a cool, dark, and dry place, preferably in airtight containers or seed packets. Label the containers with the seed type, variety, and date of purchase or testing to stay organized and keep track of their shelf life. Consider planting the oldest seeds this growing season.
I store our seeds in a beautiful wooden box that my father-in-law made me. I sort seed packets by type (tomatoes, pumpkins, etc.) and place them in zip-lock bags with a coffee filter sachet filled with cornstarch. This keeps moisture out.
Future post coming: How I Store Our Seeds
Planting the sprouted seedlings
After the seeds had sprouted I carefully planted the baby tomato plants in seed starter mix, watered them, and placed them in a sunny window.
We have since built a greenhouse so they are now out there doing beautiful and waiting to be planted in our tomato patch.
My tomato seed results
These Martino's Roma tomato seeds from Seed Savers Exchange were packaged in 2018 and I got excellent germination results!
This is Black Krim from Botanical Interest Packaged 2021. Excellent germination!
These Chadwick Cherry seeds from Burpee were from 2013. I did get 2 seeds to sprout! I was amazed! They're 10 years old!
Sweet 100 from Burpee packaged in 2017. About half germinated!
These Purple Calabash from Baker Creek were the only seeds that didn't germinate. They were 10 years old sp I wasn't expecting much.
Cherokee Purple from Botanical Interests packaged in 2021 had 100 percent germination!
This was super impressive! These grape tomato seeds from Chas C. Hart Seed Company are 10 years old! Packaged in 2013 and more than a quarter of the seeds germinated!
Bumble Bee from Botanical Interests packaged in 2016. About half germinated. I didn't have many of these seeds left.
Gigantic from Livingston Seeds packaged in 2020. Almost all the seeds germinated!
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