Does Grass Seed Expire Or Go Bad? Plus 3 Simple Steps To Check

So you’ve taken a look at your lawn and noticed it’s a little bare. You decide it’s time to use that old bag of seeds you’d kept in your garage. But what if I told you that they may have expired? 

I got you thinking there, didn’t I?

Now that you’re worryingly asking yourself ‘does grass seed expire’, let me cut to the chase and explain whether you can still use that old bag of seed. 

Grass Seed Shelf Life 

Just like most other natural products, grass also has a best-before date. As a rule of thumb, try to use seeds within 2 to 3 years of purchase. Keep in mind that with each passing year, the chances of seed germination will lessen by around 10-20% after the first 2 years of storage. 

Let me give you a quick example: 

If you have a 10 year old bag of seeds, you may only see around 1 in 5 seeds germinating. Not good, right?

Try to use those seeds whilst they’re fresh or, at the very least, within the first 2 years of purchase. Having said that, it all depends on how you store your seeds…but more about how to store them later.

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So How Long Will Seeds Keep? 

How long grass seed keeps is not quite as simple as stamping an expiry date on the bag. An unopened bag of seeds may last longer than an opened one but the way you store it does make a big difference in how long it will remain viable.

A properly stored open bag can last up to 18 months, while an unopened bag will last for at least 5 years. How do I know this?

Well, according to those who know more than I do — i.e., the experts at the Oregon State University Seed Lab — grasses that grow in hardiness zones 3 to 9 (like ryegrass) can last up to 5 years, provided the seeds are kept in ideal storage conditions. 

The other common turf varieties like Bermuda or fescue can typically last up to 3 years in storage. But keep in mind that the chances of germination are still reduced whilst in storage, so you’ll need to use more seeds to cover an area as a percentage of it won’t sprout. 

Will Grass Seed Go Bad When Expired? 

Good question! If there are no visible signs of the expired grass going bad, it can be quite difficult to tell since the expiry date on the bag is only a rough estimation. It all depends on how you store your grass seeds. 

In case you’re of two minds about sowing the expired seeds, inspect the seeds carefully for signs of fungi. If they are clumpy or damp, throw them away. This means you haven’t stored them correctly. 

Do Expired Seeds Still Grow? 

I can tell you from my experience that planting expired seeds won’t impact the end result. Why?

Well, does seed expire? Yes, if you go by the manufacturer’s expiry date on the packet. But does this affect seed germination?

Most people rely too much on the expiry date of the products they buy. If you look at the date on a packet of grass seeds, it may have a ‘sell by’ or ‘best before’ date on it. Additionally, some seed packages also include a ‘sow by’ date, which doesn’t even indicate the freshness of the seeds.

You’ll still get healthy growth from expired seeds, just as you would with their fresh counterparts. But just to be on the safe side, check the germination success of your expired seed by conducting a simple test. I’ll explain how to do such a test further down.

does grass seed go bad

How To Store Grass Seeds

I bet you couldn’t wait for this part! Right, here it goes…

The storage conditions of grass seeds are a major factor in longevity. While most people may recommend an outside shed or garage for storing your seed, those locations aren’t ideal due to the exposure to humidity and heat.

If I told you to store your sealed bag of seed next to your carton of milk in the fridge, you may start frowning because of the lack of space in your refrigerator.

Okay, this may not work for everyone. Instead, try to find the coolest location in your home, like the basement or cellar. Anywhere that is completely dry with temperatures between 40 and 55 degrees Fahrenheit will work. 

But before you say, “Phew, that was easy!”…. we’re not done yet with the seed storage advice! Keep reading for a few more pointers.

Useful Seed Storage Tips 

  • The storage location must be dark, cool, away from direct sunlight, and free of humidity, preferably in an air-conditioned room. 
  • Even if the bag of seeds is unopened, ensure adequate airflow circulates the bag.


Store the seeds in a breathable bag with mesh air vents or something similar. The mesh prevents insects from accessing the seeds while allowing optimal airflow. Burlap will also suffice as the idea is to prevent mold growth and allow maximum airflow. 

  • Keep bags of seeds separate from each other to minimize moisture buildup.


Place a container of baking soda inside the seed bag to reduce the chances of moisture or fungi. 

  • If you’re not going to use an entire bag of seeds to cover your patchy lawn, make sure you store the remaining seeds properly in the mesh bag or burlap I mentioned earlier. 
  • Remember, if you want to use the old grass seeds that have been stored for longer than 3 years, you must sow the ground more heavily for better results. 

Can Grass Seed Freeze?

Freezing your grass seed won’t affect its viability, as long as the freezing is for a short period of time.

Sown seeds often remain idle during freezing temperatures, so there is no reason why you can’t temporarily freeze unused seeds. All in all, one or two short freezes shouldn’t impact the quality of your grass seeds. 

How To Check If Seeds Are Viable In 3 Steps

Now it’s time to try my seed testing hack. This is an easy way of checking the viability of your expired grass seeds as some are likely to remain good long after they’ve expired. 

Step 1: Take a paper towel and slightly moisten it with water.

Step 2: Place 5 or 6 seeds in the paper towel and put them in a warm location. I would suggest you place the towel on top of the clothes dryer or radiator.

Step 3: Wait for a couple of days to see if any of the seeds sprout. 

And that’s it! So before you go throwing out your expired grass seeds thinking they’re not okay anymore, try this test first.  

Conclusion: Storing Grass Seeds

Yes, grass seed does expire. But whether it goes bad entirely depends on the way it’s stored. The cooler and drier the storage conditions are, the longer the seeds will remain viable, but each year you will see a reduced germination rate.

Grass seeds that are kept in a sealed container and stored in the fridge usually enjoy the best longevity. But since this isn’t practical for most people, you can just keep them in the coolest and driest room of your home for up to 5 years.  

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