How to Test Seed Viability & Germinate Seeds Quickly
It’s seed starting season! What an exciting time of year for gardeners! Today I’m going to share a quick and easy way to kickstart the germination process using a paper towel or coffee filter. This is also a simple test for seed viability if you aren’t sure your seeds are still good.
Fun fact: seeds aren’t only “good” or viable for one year. As a beginning gardener it was a relief to learn that all those seeds you get in a seed packet do not suddenly go bad after one season. Now, the time it takes for a seed to lose all viability depends on many factors—the quality of the seed, the type of seed, how it was stored, etc.—so that’s something you can do a little research on depending on the specific seeds you are curious about. If you are unsure if your seeds are still good….well, try this experiment to test for seed viability!
Not only is the seed starting method I’m about to share with you great for testing viability, but it can also help you jumpstart the germination on typically “hard to germinate” seeds.
Using a paper towel (or coffee filter) to test seed viability
Traditionally, I’ve used a moist paper towel to test my seed viability, but recently I was out of paper towels and tried one of our compostable coffee filters with great success! Both work, and both can be composted after using for this seed germination DIY.
This method also utilizes a plastic zip-top bag, but I simply turn mine inside-out afterwards and let mine dry out to use again.
What are some reasons for starting seeds on paper towels?
If the seeds you are starting are known to take a long time to germinate. Peppers are notorious for needing heat and longer times to germinate, and I have found they love this method.
Are you wondering if your seeds are still good? We call this seed “viability” and this is an easy method for testing if your seeds are still viable.
Save on space and resources. Sprouting seeds on a paper towel can allow you to know which seeds are good and only plant the seeds that sprout into seedling pots, seed starting media, etc. It’s a great way to increase your chances of success with less investment!
Pepper seeds can be difficult to germinate, but I have found this test for seed viability also works wonders for pushing the germination on pepper seeds.
On the other hand, despite the benefits of this little garden experiment, don’t forget that the good ole seed starting basics still stand. This seed viability test or shortcut is just another tool in my garden toolkit. After germination, I simply proceed with the steps in my Basic Seed Starting Guide.
Do I use a seedling heat mat?
You don’t need a heat mat for the paper towel method to be effective, but I can report that my pepper seeds germinated much faster when I used a heat mat. I have a very inexpensive yet efficient heat mat from Vivosun that you can check out HERE.
Do not use a heat mat for seeds that don’t like heat because it is possible for it to be too hot for a seed to germinate. There is also a chance of growing mold or causing the seeds to rot when using a heat mat. You always want to understand the preferences of each plant in order to know if a heat mat would be a good fit.
Supplies to Germinate & Test Seed Viability
Your seeds
Paper towel or compostable coffee filter. You can find the coffee filters HERE. I also am using paper towel halves so they easily fit in the zip-top bag.
Water
Seedling Heat Mat (optional, see notes above)
Gathering my materials to test seed viability and promote germination. These are compostable coffee filters but you could also use paper towels.
How to Sprout Seeds with a Paper Towel or Coffee Filter
Assemble your seeds. For this article I started some shishito pepper seeds (they make the best fire roasted appetizers), pineapple ground cherries, and eggplant. You might notice that all these seeds like heat and so I used my heat mat as well. Note: I also tried a few dahlia seeds with this method but I don’t recommend it as much for them. I had a better experience growing mine in seed starting mix.
Label your zip-top bags. This is essential if you want to remember what you are germinating!
If using coffee filters, I find it helpful to cut them in half like the photo below. This makes it easier to fit in the zip-top bag and we can save on using more coffee filters!
Moisten your towel or filter. It is VERY important that they are not sopping wet. For the paper towel, I run it under the faucet for just a second, wring it out, and unfold it. The coffee filters become moist much faster, so I tend to quickly put it under the faucet and then press the filter between my hands to “wring” it out.
Both of the seeds above like heat, so I opted for the heat mat. Starting seeds using a paper towel or coffee filter takes less space for me, and I will only plant the viable sprouts!
Put your seeds on the moistened towel or filter and fold it down over the seeds.
Place the towel into the properly labeled zip-top bag and seal.
Leave your bags in a warm area of your home, but not in direct sunlight. Too much sun can cause algae to grow.
You can see below that I’m using my heat mat for this particular group of seeds, so I just place them on my mat.
Watch & Observe
I like to check on my seeds every day to inspect for signs of mold and for germination. The quicker you spot the germination, the better.
If it looks like your paper towel or coffee filter might be drying out, open the bag and spritz with your water bottle. Seal the bag again.
Here are some of the newly germinated seeds in the coffee filter! I was unsure about the viability of the ground cherry seeds, but it looks like they were great!
Planting Your Sprouted Seeds
To plant a seed after germinating on a paper towel, simply bury it in pre-moistened seed starting mix. You want to bury it to cover the white parts, leaving the green parts above the soil surface. If there are no green parts (like in my photos) I literally place the entire thing under about 1/8″ of soil and it eventually breaks through!
I prefer seed starting mix because it is light and fluffy. You can learn my favorite DIY seed starting mix recipe or all the options for seed starting media HERE.
It’s a good idea to handle the seed delicately (because they are so fragile at this stage!) by holding the seed coat. The “seed coat” is basically the shell cover of the seedling—-some people also call it the seed “hat.”
Continue to keep the seed starting media moist, using water in a spray bottle if necessary. At this point, the process is the same for most seed starting so make sure to read my guide for starting seeds.
My newly sprouted baby eggplant.
Get growing!
I hope you enjoyed this little trick for starting seeds and testing seed viability. Remember that the best time to start seeds will depend on your gardening zone (find your zone) or climate. If you are a fellow Southern California or zone 10 gardener, please make sure to subscribe to my free email newsletter to view my personal seed schedule (available in the Garden Resources Library).
Other articles you might find interesting:
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Meet Randi
Randi!!! Hola my friend! And of course I want to say a quick hello to Sam and Pete so hola as well 🙂 Absolutely love this article becasue its one of the main methods I use for peppers when I have limited amount of seeds or when I’m trying things I’m not to sure how hard they are to germinate. Especially becasue I don’t use a heat mat it seems to work easily and exactly like you mention, it’s nice to be able to “see” which seeds did germinate to make it even easier! I haven’t tried coffee filters but it makes perfect sense they would work just as good! Thanks for sharing this tip and trick as you for sure explain it way better than I’ve ever did when tried to… hahaha… Anyways, hope you guys are well and enjoyed your weekend! Thanks again for taking the time to share my friend 🙂
Hola Rod! So glad you enjoyed the article, especially since you already know and practice this method. Do you like to plant them as early as I show in the photos (just sprouted)? Or do you wait longer?
Hola again Randi! I will plant them in my cups like you show them here, just sprouted, but honestly there’s times where I haven’t kept an eye on them and the get bigger. I’ve even transplanted them when they have already emerged completely from the seed coat! I’ve done 2 things at that point if the seedling is still hooked over as if was trying to break a surface I bury it so the hump of the stem is just above the surface but the (I can never remember the true name) “baby leaves” are in the seed starting mix. If the “baby leaves” have already straightened out, I bury just the stem and leave them “baby leaves” just above the seed starting mix… even if they ate not straight up they correct themselves rite away. Both methods have worked for me but like you mentione here in your article, I prefer to try and stay on top of them as to transplant them as soon as the root tip emerges from the seed coat. Hope that was understandable my friend… as I know one of my weaknesses is explaining things hahaha 🙂
All good info! It’s good to know the different scenarios. It’s incredible how strong and resilient these teeny tiny seeds are!
Hi! I have a question…can I remove the seeds from a freshly harvested pepper, put seeds in the water to see which float and which do not, separate them and then dry the viables for a future planting? Thanks
Hi Linda, I can’t attest to the accuracy of a float test personally. What I’d do instead is dry the seeds and then, when you’re ready to start seeds, use the coffee filter/paper towel method to attempt to germinate a larger number than you’ll think you need. The nice part about this type of seed starting is that you can “test” a lot of seeds without wasting soil and space. This also allows you to plant only the seeds that germinate, which is wonderful! Hope that helps.