Have some old seeds lying around? You’re probably wondering if they are still good for planting or not. We’ve all been there! No one wants to wait around for dud seeds to fail when you’re following a seed-starting timeline.
Not only is it disappointing, but as a zone 4A Minnesota gardener, our season is way too short to mess around with non-viable seeds.
The good news is that a seed viability test is super easy to do at home and you don’t even need soil for this method, which is great. No mess! This would also be a great experiment to do with your kids to observe how germination works in such a visible way.
*Disclosure: This post may contain affiliate links to products (including Amazon). I’ll earn a small commission if you purchase through my link, at no additional cost to you! Regardless, I only link to products that I personally use on our homestead or believe in.
What Is the Average Seed Viability?
When deciding which seeds to test for viability, it’s important to know how long you can expect them to last (as long as they are stored properly – more on this later!). For example, a 3-year-old package of peppers should be tested while a 3-year-old package of basil likely does not.
- 1-2 years: Chives, corn, leeks, onion, parsley, parsnip, pepper, shallot, spinach
- 3-4 years: Asparagus, beans, beets, broccoli, brussels sprouts, cabbage, carrots, cauliflower, dill, eggplant, fennel, kale, kohlrabi, peas, squash, thyme, tomatoes, watermelon
- 5-6 years: Artichoke, basil, celery, cucumber, endive, lettuce, melon, mustard greens, radish, turnips
How to Do a Seed Viability Test
A seed viability test is super easy to do, but it requires a little bit of patience while you wait for them to germinate. That’s the hardest part! Grab your seeds in question and let’s see how they do!
Supplies
- 10 seeds
- 1 paper towel
- Ziplock bag (quart or gallon size)
- Marker (optional)
Step 1: Soak the seeds
The best way to mimic moist soil to promote germination is a wet paper towel. It makes for a clean experiment, too! Run a paper towel under the faucet until it’s fully saturated and then let it drip slightly so it’s not absolutely sopping wet. Not too wet, and not too dry.
Fold the wet paper towel in half and set it on a solid surface. Place 10 seeds on the paper towel (giving each one a little wiggle room!) and then fold the paper towel in half again. Gently press down on the paper towel to ensure that all surfaces of the seeds are in contact, then carefully transfer to a ziplock bag and seal.
Don’t forget to label the bag with what seeds you’re testing (especially if you’re testing multiple varieties at one time)!
Step 2: Wait for germination
Most seeds like warm temperatures (70F) to germinate properly, so don’t throw the test bag in your cold basement or back cupboard. My favorite spot is near our wood stove, but above your fridge would work well, too.
Keep in mind that a few kinds of seeds (mostly herbs) need light for germination: arugula, basil, dill, lemon balm, okra, oregano, sage, spearmint, sorrel, tarragon, and thyme. If you’re testing the viability of these, set the test bag near a sunny window.
Make note of when germination should be expected (your seed packet should say) and mark your calendar. Most seeds germinate within 7-14 days (or sooner!), but some things like carrots, parsley, and artichokes take a bit more time. Check the paper towel every few days and re-moisten if it starts to dry out.
Step 3: Assess for viability
Once the proper amount of time for germination has passed, it’s time to take a peek! Carefully pull out the paper towel, open it up, and observe how many of the seeds have germinated. Since we’re using 10 seeds, it’s easy to figure out the germination percentage!
Out of the 10 seeds tested:
- If 0-5 have sprouted (0-50% viable), it’s time to toss them!
- If 6-7 have sprouted (60-70% viable), it’s worth hanging on to them, just be sure to seed a little heavier to account for a lower germination rate.
- If 8-10 have sprouted (80-100% viable), they are still in great condition for planting.
*If you’re not quite sure of your results, put the seeds back into the ziplock bag for another few days to give any late ones a chance to rally.
Now that your test is complete, you can toss the seeds into your compost pile, feed them to your chickens, or place them in some seed starting mix and let them keep going! If you plan to do the last option, check out my article How Often to Water Seedlings to make sure they are off to a good start!
How to Store Seeds for Maximum Viability
I’ve totally messed up my seeds before by storing them improperly – it’s so disappointing! Seeds need 3 things to germinate: temperature, light, and moisture. If you control these 3 things, then they should remain dormant and viable for planting.
Temperature
Most seeds prefer warm temperatures (usually 70F or so) for germination, so keeping them at a cooler temperature will help ensure that they don’t try to get too active on you. The best is 35-40F (fridge) and the second best is 40-55F (root cellar). Pro tip: Let the seed packet come up to room temp before opening it to reduce the formation of condensation.
However, seeds don’t like temperature fluctuations! So, if you’re bringing your seeds back and forth between the fridge and your warm house for different rounds of seeding and over several years, this can become an issue.
My fridge is often full and I prefer not to deal with all the back and forth, so I simply keep my seeds in my seed organizer box on a shelf in our living room. Yep, I’m a rule-breaker. I’ll occasionally come across a packet of non-viable seeds, but for the most part, things have been just fine!
Light
This one is pretty easy to avoid since seed packets are usually made of solid paper and aren’t see-through. Even still, be sure to keep the packets out of direct sunlight to avoid rapid degradation of your seeds. A garage, basement, or closet is best!
Moisture
As we’ve seen in this seed viability test, moisture plays a BIG role. Ensure that you’re storing your seeds in a dry location and away from places with lots of moisture like bathrooms, laundry rooms, and even your seed starting room. Better yet, store your seeds in an airtight container.
FAQ About Seed Viability Testing
When should I do a seed viability test?
It’s not necessary to test ALL of your seeds, every season. I only do a seed viability test if their quality is in question. This could be due to their age (check out the section above on average seed viability if you missed it!) or the conditions in which they were stored. If the packet spent the summer in a hot attic or if it was rained on when left outside, it’s definitely a good idea to test!
How accurate is the water test for seeds?
The water test is another method that can be used to test seed viability, but it’s not as accurate as the germination test that I recommend above. The water test involves placing seeds in a glass of water, waiting 15 minutes, and evaluating their behavior. If the seeds sink they are “good”, and if the seeds float they are “bad”. I like that this is a quick test, but again, it’s not very accurate as many factors can go into whether a seed sinks or floats.
What is the TTC test for seed viability?
The TTC test is not for the home gardener and is usually done in a lab. It involves cutting open a seed embryo and applying a TTC solution to stain the cells. This allows the scientist to quickly see if the seed is viable based on whether or not the embryo accepts the stain.
Are 10-year-old seeds still good?
It depends on the seed and the condition that it’s been stored in! If it’s a seed that has a longer expected viability time (like a cucumber) and it is stored in perfect conditions, it very well could still be viable after 10 years!
Other Gardening Articles You’ll Love:
- 15 Vegetables (and Herbs) That Grow in Shade
- Using Mulch in the Garden: A Comprehensive Guide
- Top 10 Perennials for a Low-Maintenance Vegetable Garden
- The BEST (and worst) Vegetables to Grow in Raised Beds
*Are you interested in starting a garden, but you’re overwhelmed with where to start? Or maybe you’ve tried a garden in the past, but it flopped? Definitely check out my course How to Plan a Garden: Step-By-Step! Don’t forget my discount code “THRD10” for 10% off!
Achieve Your Best Harvest Yet!
Grab your own FREE copy of my Garden Growing Guide. It’s fully customizable to your growing zone and can be printed or used digitally. Happy Gardening!
Hello, Really enjoy your YouTube videos and emails. Your videos are so interesting and informative!! I also live in Minnesota (Twin Cities area) and love to garden and look at other gardeners ideas. Take Care and hope you are enjoying our winter weather.
Thank you so much, Patricia! I love that you’re in Minnesota, too 🙂
Thank you for this great method to test the germination rate!
As you say, our seeds degrade over time. I would like to point out that an old seed that germinates might not have all the desired characteristics that it had in its youth. For example, a bean has a lifespan of 3 years to 5 years (when stored in optimal conditions). But if it germinates at 5 years old, it may have lost some characteristics. It is therefore always best to sow a seed as young as possible. I have taken this from an excellent resource on seed collection and saving, from which the following is an excerpt: https://seeds.ca/books/
“All seeds in the same batch have slight genetic variations (and) some have a trait that allows them to survive longer in storage. When a batch of seeds with a low germination rate is sown, the seeds that have survived are actually a natural selection from the original group. They have a genetic trait that allows them to be preserved longer, but other traits will also be linked to these seeds. They will therefore have different characteristics from the original population. This is called genetic drift.” (p.26).