So it’s spring or fall and you want to overseed your lawn. Or perhaps you want to fill in a few dead spots with the seeds you saved back after seeding your lawn. Before you do, however, you may want to check those seeds to avoid wasting a growing season. You can learn how to do that below.
How to Tell if Grass Seed is Still Good (The Short Answer)
The best way to see if grass seed is still good is to do a germination test. The problem with that is that quite a few seed varieties have average germination times of 2 weeks or more. If your planting window is closing, a safe bet is to throw out and replace anything older than 2 years.
How to Tell if Old Grass Seeds Will Germinate (4 Simple Tests)
The best thing to do to fully evaluate your grass seed would be to conduct a germination test. However, there are a few simpler tests you can do before you spend several weeks on one of those tests or while you’re waiting on the results.
The Visual Test
Before setting up any sort of complicated test, take a look at your seeds. You’re going to take a handful of the seeds or a small scoop of seeds from the bottom of the container out and place them on a plain white piece of paper.
If you see any insects, evidence of insects, discoloration, empty hulls or husks, powder or dirt, mold, fungus, or anything that doesn’t look like pure, clean seeds- you may not want to plant these grass seeds.
Contamination doesn’t necessarily mean that your seeds are dead, but with how fragile and inexpensive most grass seeds can be, I wouldn’t plant any that were contaminated or damaged. You can read a more in-depth explanation of the signs you’re looking for in the following section.
The Weight Test
In addition to the visual test, it’s important to weigh your seeds. As a general rule, seeds will lose moisture and mass over time if stored improperly and as they deteriorate. Most guides for planting a new lawn will advise you to keep 1 to 2 pounds of seed back.
If you know how much grass seed you kept, you can weigh your seeds. If they lose 5% or less of their initial weight, they are likely to deteriorate to the point of slow or reduced germination. In this case, you can plant your seeds, but you should plant more of them.
A germination test can help you determine how much more you will need to plant. If the seeds are 10% or more lighter, it’s best to throw them out and start with fresh seeds.
A Simple Germination Test
How to tell if seeds will germinate when you plant them in your yard? Do a germination test. All you need is a clean, damp paper towel, a clean container with a tight-fitting lid, a warm place like the top of your refrigerator or a windowsill, and 10 or 20 seeds.
First, you want to wash your hands and your workspace. Then you should lay out the paper towel and double it if it’s a full or half sheet. Then carefully, with dry hands, place 10 or 20 seeds on the damp paper towel, not touching.
Carefully fold the paper towel over these seeds again and place the bundle into the container. Put another few drops of water into the container and seal the container. Place the container into the warm spot for half the time for whatever your grass seed’s average germination time is. Once it reaches this time, check to see if anything germinates.
Keep checking your seeds every 3 days to note if there has been any germination. After the average and expected germination time has passed, note what percentage of the seeds have germinated. If you “planted” 20 seeds and 14 have sprouted, you have a germination rate of 70%. This is excellent and means that the seeds can be planted as usual.
If you planted 20 seeds and only 10 germinated, your seeds are still acceptable but you will need to plant double the number you would have planted if they were new. If fewer than 5 seeds germinate out of 20, you should buy and plant fresh seeds.
Any more than 5 and less than 10 is a judgment call, but I wouldn’t plant any grass seeds with a germination rate of less than 50% unless they were a variety with a low germination rate, to begin with.
The Water Test
This test is only being mentioned because so many places online mention this as a viable option. It is not. The water test does work on other types of seeds to an extent, but due to their size and shape, it is not a viable way to test grass seeds or any other type of seeds with a small, flat, and coarse shape.
In the water test, you would fill a clear container with water and drop about 20 seeds into it. The theory goes that if the seeds float they are no longer viable. If the seeds sink, they’re fine.
The problem is, plenty of brand-new grass seeds will float due to how they’re shaped and how light they are even when fresh. Therefore, the water test is not a good method of how to tell if grass seed is still good.
8 Signs That Indicate Old Grass Seed is No Good (Throw It Away)
How do you know if grass seed is still good? Make sure you don’t see any of the signs listed below, then conduct a germination test.
Signs of Infestation or Pest Damage
If there is any evidence of infestation or rodent damage, throw out these seeds. This is both a physical and contamination risk that’s not worth the trouble and that likely means your seeds were not stored or were not harvested properly.
Empty Hulls or Physical Damage
If you see no direct pest or insect damage but you’re seeing a lot of empty hulls or broken seeds, the same advice applies. This can be a sign of damage by neater pests or general deterioration.
Your Grass Seeds are Lighter (By Weight) Than They Used to Be
As mentioned in the “weight test” section above, grass seeds will weigh less as they begin to deteriorate. If they weigh 10%, or more than 10%, less than they did before, it’s important to either give up on them or conduct a thorough germination test.
Do not allow seeds longer to germinate that recommended by the distributor or manufacturer as this can allow damaged or malformed plants to take root.
The Grass Seeds Have Gone Pale
The first visual indicator that your grass seeds have gone bad is a pale appearance. As grass seeds deteriorate they may lose their color. This is not a definitive sign that your seeds have lost their viability but it is a good indicator that they should be tested before use.
Mold or Fungus is Present on the Grass Seeds or There is a Musty Smell
If there is any sign of mold or fungal growth or if your seeds have become “dusty” when they weren’t before- don’t keep those seeds. Mold and fungus may not have taken place yet but planting those seeds and providing them with water and nutrients can cause mold or fungus to infect not only those seeds but also get a foothold in the rest of your lawn.
The Grass Seeds Have Been or Are Damp
Damp is unacceptable when it comes to stored seeds. If there has been any hint of dampness during the storage period, replace these grass seeds.
There is Evidence That The Grass Seeds Have Sprouted
If the seeds were allowed to become damp and warm, they may have sprouted in their packaging. In this case, the seeds have already done all they are going to do, and planting them will only lead to deterioration.
Your Grass Seeds Are More Than 5 Years Old
Will old grass seed germinate? Maybe. However, grass seeds that have been in storage for more than 3 years carry a significant risk that they will have a very low germination rate. They also carry the risk that if the grass does manage to germinate, it will be malformed or unhealthy and take much longer to grow than the rest of your lawn.
Make sure to check the date on the original packaging or keep your original purchase receipt. If it has been more than 3 years since the initial harvest or purchase, it is best to replace these seeds. For a more in-depth explanation of why this is the case, see my explanation of how long grass seed lasts and why it goes bad.
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