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how to tell if seeds are viable

How to Know If Garden Seed Is Viable

I have old packets of seeds. How can I tell if they are still viable?

seed

Answer: Most seeds last for several years, however others have a relatively short life. How do you know if your seeds are still viable? When properly stored in a cool, dry place, seed’s shelf life can be extended. Yet, even then, there is no guarantee that they will still be productive for next season’s planting. There are two easy tests you can take to check to see if there is life left in your old seeds.

Water test: Take your seeds and put them in a container of water. Let them sit for about 15 minutes. Then if the seeds sink, they are still viable; if they float, they most likely will not sprout. This method, in my opinion, is not the best way to check your seeds. For surer results, try performing a germination test.

Germination test: Take some of your seeds, preferably 10, and place them in a row on top of a damp paper towel. Fold over the paper towel and place in a zip-up plastic bag and seal it; this helps to keep the towel moist and protected. Then put in a warm location, like a high shelf or on top of the refrigerator, and check the seeds often—around once a day—to see if they have began to germinate and/or to check the moisture of the paper towel. If it needs more water, carefully mist the towel to where it is damp, but be careful not to apply too much water. Make sure the location you have chosen is away from exposure to direct sunlight. This can overheat your seeds.

Your seeds should begin to germinate in several days up to a couple of weeks, depending on the seed-type. A good rule of thumb is to wait roughly 10 days; however, if you want to give your seeds the best chance, research the germination time of your specific seeds. Once the allotted time has passed, check to see how many have germinated. If you placed 10 seeds on the paper towel, this will be pretty easy to calculate. If less than 5 seeds sprouted, your old packet may not have much success when it comes to planting. If more then 5 sprouted, than your seeds still have a lot of vigor left in them!

Some people wait to perform this germination test around the time of planting, so that the successfully sprouted seeds can be placed directly in their garden—a good way to cut time and ensure the plants will flourish beautifully outdoors.

No matter what step you take to test the viability of your seeds, always remember that every seed is different and your results may vary. With success, you can help your little seedlings sprout into the magnificent, thriving plants they were meant to be.

Image: Jeffdelonge
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If you have an old packet of seeds, here are some ways to determine if it is worth planting.

How To Test Old Seeds

Sometimes, we have seeds that have been around for a while and we either aren’t sure of their age or are unsure of how viable they still are. Seeds from professional seed houses and gardeners will usually have a 90% germination rate within a 2-3 year span of their packaging.

If you have old seed packets or want to test your own harvested seeds for viability, then there are two common methods for doing so.

Each of these methods can be used with a random sampling of your seeds (10-20 seeds or 10-15% of your total seed in that variety) or with all of your seeds you intend to plant into the garden beds or starter pots right away. The random sample will tell you the percentage of your germination. So if you try 10 seeds and 8 of them germinate, you have an 80% germination rate.

Be aware that once the seeds are tested, you will need to either plant them immediately or be prepared to throw them out. So if you aren’t near gardening season yet, use a random sampling rather than all of your seeds.

Soak Test for Old Seeds

This is the easiest of the methods. Simple put the seeds into a cup, jar, or bucket of water and allow them to soak. Bad seeds will continue to float indefinitely while good seeds will sink within a few hours.

Give the soak about 12 hours to work, then skim the bad seeds off the top and throw them onto the compost heap. Drain the water through thick cloth, a very thin sieve (depending on seed size), or similar and retrieve the good seeds. They will need to be kept moist and planted within a few hours.

Damp Towel or Cloth Test for Old Seeds

This germination test requires a bit more work and time, but is more reliable than the soak test method. Using a damp cloth or paper towel, place seeds in a single layer across half of it. Then fold the other half over them to cover. Place in an area that is room temperature (closet, cabinet, etc.) and keep moist. Many put their seeds into an unsealed plastic zipper or freezer bag.

Check daily to keep it moist and after 3-4 days, begin lifting the towel gently to look at the seeds. In most cases, all of the seeds which will germinate will do so within 10 days.

Using Less Reliable Seeds

If you used a random sampling and found your reliability to be 50% or better, the seeds are still likely good enough for gardening. Simply increase the rate of seeds per foot/row/hole to make up the difference. So if your germination rate was 50%, double the number of seeds used.

If your germination rate was below 50%, you can either use the above heavier seeding method or throw the seeds out. It’s advisable to throw them out and replace them with others if possible as the extra seeding and resulting culling will require a lot of extra time and effort.

Want to learn more about testing old seeds?

Check out these Resources:
Growing Vegetables From Seed from University of Tennessee Agricultural Extension Service
Seed Germination from Washington State University

seeds in hand seed sprouting with text overlay how to test old garden seeds before planting

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Comments

Kathy says

I have always used the method with the wet paper towel. I think I might try soaking some old seeds for awhile first next time to see if that helps to increase the germination rate.

How To Test Old Seeds Sometimes, we have seeds that have been around for a while and we either aren’t sure of their age or are unsure of how viable they still are. Seeds from professional seed