How Long Does Grass Seed Last Before It Expires?

When you notice a spot on your lawn that needs more grass, the first thing you’ll probably do is check whether you still have some grass seeds left in the shed or wherever it is that you keep your seeds.

However, how long does grass seed last?

Here, I’ll let you know whether the old grass seeds that you have are still good to germinate.

Grass seeds are classified into two main types: the ones that are good for the cool season and the warm season. It’s generally easy to germinate grass seeds and you can even store them for a few months.

However,the success of germinating your grass seeds is also determined by how long you’ve stored them.

This is why it’s best to check how long your grass seeds were stored for you to know if they are still viable.

So how long can you store grass seed?

Generally, the ideal storage time is just 10 to 18 months. You can still use seeds that are stored beyond 10 months but you can’t expect that 100 percent germination will happen.

This means that seeds stored for more than 10 months can still germinate but you may notice a decrease in its germination rate.

There are also other factors that should be considered when storing your seeds to make sure that you can still use them. 

Read on if you want to know what these are and for you to determine whether you still have good seeds.

Related post: Seasonal Lawn Care Guide and Tips

how long does grass seed last?

how long does grass seed last?Pin

The general rule of 10 to 18 months is really the safest answer.

This means that if you store your grass seeds for only that long, all of them are most likely going to germinate. A pack of fresh seeds can germinate from 90 to 100 percent most of the time.

If it has been more than a year since the packing or manufacturing date of the seeds, then expect that not all the seeds in that pack will still sprout.

You may end up wasting time and effort to grow non-viable seeds if you choose to grow ones that are more than a year old.

The Decrease Of Germination Rate

Know that the shrinkage rate of the germination of these seeds is at 10 percent a year. Even if the label states or claims that the seeds can germinate up to a hundred percent, it will eventually decrease.

Sometimes, it won’t even take a year for this to decrease. The storage condition is really key when it comes to making your seeds last.

There are also some who would claim that grass seeds are good for two to three years. However, this will really depend on the storage of the seeds.

If the seed packet that you got claims that the seeds will still grow with a rate of 90 percent after a year, this probability will simply decrease each year.

Personally, it’s just really ideal to store unopened or unused grass seeds for less than a year.

If the storage time goes beyond that, it just means you’re risking trying to grow seeds that may not even germinate or grow as grass anymore.

Factors That Affect The Success Of Your Grass Seed Germination

Factors That Affect The Success Of Your Grass Seed Germination - overseedingPin

The way you store your grass seeds plays a crucial role when it comes to ensuring that they will still be viable within a year or more than that.

The general rule is that they need to be placed in a dry place, but here are some other factors you should look into.


It’s best to store your seeds in a sealed plastic bag or container. You can purchase zip locks for this, but just be sure that these storages are completely dry to avoid moist from building up.

You can store grass seeds in your garage or shed as long as these places are not considered hot or humid.

If possible, you can even store your grass seeds in your fridge as this can guarantee that your seeds will be placed in a cool place.

In fact, seeds that are placed in a sealed bag and placed in the refrigerator has more chance of having longer viability.


Aside from the storage being dry, the temperature is also something you should check.

It’s typical for gardeners to store their seeds in sheds or garages, but know that the seeds should be placed where the temperature is cool.

The ideal temperature of your storage place should be under 60 degrees Fahrenheit.

Do not place your grass seeds in places with above 100 degrees of temperature if you still want to use them in the future.

Monitor the temperature in your shed or garage if your seeds are kept there and be sure to keep them cool when the temperature rises to more than 60 degrees.

Humidity And Moisture

New Grass with grass seeds in betweenPin

Seeds can absorb humidity and moisture. This is why you should keep them in a cool room in the first place.

When your seeds absorb more moisture than it should when it’s stored, they’ll end up non-viable. They most likely won’t germinate.

The internal seed moisture level is ideally 10 to 20 percent. You can control the moisture and humidity that they can absorb by avoiding humid temperature.

You can get a dehumidifier or an air conditioning unit placed in your storage room for this.

Is There An Expiration Date?

If you purchase your grass seeds in packs, then you will indeed see an expiration date. If the grass seeds are expired, according to its package, I suggest that you don’t waste time on it anymore.

Even if these grass seeds are sealed and left unopened, the expiration date simply indicates how less likely you’ll have these seeds germinate.

If the expiration date is still far from when you need to use the seeds, you should also check when the pack was manufactured.

Follow the 10 to 18 months rule as it still applies. This will also let you know whether the pack of seeds that you have will completely germinate.

How To Tell If The Grass Seeds Are Expired

How To Test The Germination Rate Of Your Grass SeedsPin

The expiration date on the packet of the seeds is really the expiration test date. This means that the seeds in the pack that you got was tested for the germination rate. The rate is typically 90 to 100 percent.

Basically, the expiration on the label of the seeds you have is until when the germination testing results or rate is valid.

After the expiration, the manufacturer will have to re-test the seeds and relabel the package with the current germination rate and test date.

Can You Freeze Grass Seeds?

Indeed, you can place grass seeds that are in a sealed container in the refrigerator. This is to make sure that you don’t expose them to humidity.

However, have you ever thought of freezing them?

Well, you can actually do this but it’s not highly recommended.

While freezing the grass seeds for a short period of time won’t really have much effect or even no effect at all when it comes to their viability, it’s still possible that these seeds will have a lesser chance of sprouting.

What you just really need to remember is that most types of grass seeds can only withstand short periods of freezing temperatures. Freezing the seeds is not necessary.

What’s important is that you avoid exposing your seeds to temperatures that are below 32 degrees Fahrenheit.

How To Test The Germination Rate Of Your Grass Seeds

If you’ve no idea how long the grass seeds that you have were stored, then the best you can do is to test how well the grass seeds can germinate yourself. What you can do is to get a few seeds and place them, inside moist paper towels. However, researchers at the University of California have a good guide on the timing of how long grass seeds should take to germinate.

You can place the moist paper towels with seeds in a plastic bag, but you don’t have to seal the bag as the moist will help with the germination process.

Let the seeds in the bag sit in a warm room or a room with a temperature of at least 40 degrees and below.

If the seeds are still good or viable, they should start sprouting on day 10.

However, some seeds could sprout as early as day 5, so it’s best that you check it every five days. If you see no sprouts after day 10, then it’s just really time to get new grass seeds.

How Long Do Grass Seeds Last Without Water

When you’ve taken out the grass seeds out of storage, they will require moisture and proper temperature in order to sprout or germinate.

While it’s important that you keep the seeds dry during storage, this isn’t really the case once you’re ready to use it outside.

Healthy germination requires water and new seedlings will also need it to survive.

In fact, it is advisable that you water your grass seeds several times a day to germinate. Leaving your seeds dry for too long during this process won’t really promote sprouting.

How To Properly Store Grass Seeds

how long does grass seed last? grass seed in gardener's handPin

I’m sure I’ve already established how important it is to keep your grass seeds dry during storage and how important the other factors like temperature are when it comes to keeping them viable. Of course, I won’t leave you with just explanations!

Here is a great way on how you can properly store the unused grass seeds that you have.

Choose A Sealed Container

While you can use any sealed containers like ziplock bags, I highly recommend that you opt for breathable packaging instead. You can opt to use cloth sacks or burlap bags for this.

The reason why I recommend breathable materials is to allow airflow and reduce the risk of molding during storage.

If you don’t have any breathable materials like the ones I’ve mentioned, you can still use plastic containers that can be sealed.

What’s important is that your seeds are dry and so are your containers. Wipe your containers dry and make sure that they won’t produce moisture once you have them sealed.

Place Labels

Labeling is simply necessary when storing seeds or anything, really. Be specific with what you write on the label.

If the seeds came from a pack, then put the name of the seeds and the test expiration date. You should also put the date as to when you’ve opened the pack.

Be specific as to what type of grass seed it is, whether it’s Bermuda or Bluegrass.

This will help minimize the trouble of figuring out what seeds you have when you already need them a year or 2 years from storage.

Look For The Best Place

If you’re using plastic containers, then you should definitely make sure that the place where you’ll store your seeds is generally cool.

Breathable storage materials can protect your seeds from moist, but it doesn’t mean that you can let the seeds sweat.

If you don’t have space in your refrigerator to store your seeds, then just make sure that you avoid placing your seeds in areas where there is too much heat. This is the mistake that a lot of gardeners have.

Avoid the shed and the garage if you don’t have air conditioning units or dehumidifiers in placed in there.

Remember that the ideal temperature where your seeds should be is around 60 degrees Fahrenheit.

Check From Time To Time

how long does grass seed last? grass seeds in storagePin

Now, even if you’ve followed the great tips I’ve shared when it comes to properly storing your seeds, you still need to check on them from time to time.

It could be every few weeks or every month. What you need to be on the lookout for is moist and pest infestations.

Rodents are most likely the pests that could be attracted to your seeds, so make sure that you check for that. The temperature should be monitored too, if possible.

Any abrupt temperature change can affect the humidity in the room. It could moisten your containers and affect the viability of your seeds.


Overall, it’s really simple to store your unused grass seeds. The general rule of storing them in a dry and cool place is what you should really keep in mind.

Avoid exposing it to the sun and anything else that could promote germination.

After all, that’s what you’re delaying to happen. If you find a random pack of grass seeds with no indication of how long it has been stored, just do some testing.

One last note, consider aerating your lawn prior to overseeding. This will help the grass seed get enough oxygen and nutrients when they start germinating.

It may take quite an effort, so if you can, just get fresh seeds to be sure that you won’t be wasting any time.

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