Does Grass Seed Go Bad or Expire? Here is the Answer!

Found an old bag of grass seed in your garage?

You might be wondering, does grass seed go bad?

Read on to learn more about the shelf life of grass seed and how to store it correctly.

Contents

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Quick Read

  • Yes, grass seed can go bad and does lose its viability over time.
  • Grass seed can comfortably last between 2 and 5 years if stored correctly.
  • Grass seed needs to be kept in a cool, dark, dry place.
  • You can still use old grass seed, even if it has expired (provided it is not moldy), but it will likely have a lower germination rate.

While you’re here, are you in need of a lawnmower? Trying to decide what kind to buy?

Have a read of my article about the benefits of reel mowers for a healthy lawn.

Alternatively, if you already know what kind of mower you’re after, I have a range of guides including the best commercial zero-turn mowers, the best battery-powered lawnmowers, the best ride-on mowers, and the best mowers for small yards. I’ve got you covered!

man holding grass seed in hand

Can Grass Seed Go Bad?

Let’s get into this question in a little more detail.

Yes, grass seed can go bad. But what do we mean by ‘bad’ exactly?

Grass seed can go ‘bad’ in two ways:

  • Over time, as grass seed is exposed to extremes in temperature, it will gradually lose its viability. It’s estimated that around 10-15% of the seed in a bag loses viability over the course of a year. Unused grass seed is a living thing in a dormant state (fascinating, right? You can read more about that here). But it can die of exposure and old age. Once this happens, the seed will no longer germinate or have the capacity to grow into anything.
  • If exposed to less than ideal storage conditions, such as humidity, grass seed can also start to harbor mold which is usually a death sentence. Exposure to light is also something you need to avoid.

But, you can maximize the life span of your seeds by storing them correctly in a dark place and protecting them from excesses in temperature and humidity.

Are you wondering whether other garden products go bad too? What about Fertilizer? I have a guide to the shelf life of fertilizer here too to help you out.

How to Store Grass Seed for Maximum Shelf Life

Now you know what grass seed doesn’t like, how do you keep it happily dormant?

Contrary to what you might think, the garden shed or your garage is likely not ideal place to store seeds. These places are often not insulated and so will likely be exposed to a wider range of temperatures than is ideal for storing seeds. Your garden shed is also more likely to be a little leaky in really wet weather and potentially expose your seeds to dampness.

Your refrigerator is actually a really good place to store seeds, but grass seeds tend to come in pretty big packets so you likely won’t have space in your kitchen fridge for long-term storage.

The best place is a cupboard or room in your house where the temperature stays consistently cool all year round. You can then fix the light and humidity issue by storing the seed in an opaque, sealed container.

Pro tip: If you have any little packets of silica beads that come in some food or medication packaging for absorbing moisture, you can chuck a couple of them in for good measure!  

But what about packaging? You might be wondering, how long does grass seed last in the bag it came in? If the bag is unopened, then humidity shouldn’t be an issue, your main objective should be to keep it cool and dark.

grass lawn in sunlight closeup

But, if the bag is opened, some people are of the opinion that grass seed should be transferred to a more breathable material like a burlap sack. I’m willing to bet this isn’t necessary and the bag the seed came in should be fine, but I’ll leave that decision up to you!

How Long is Grass Seed Good For?

Assuming you’ve followed the guidelines above and kept your grass seed in a consistently cool, dark, dry place, you’re probably wondering how long it will actually keep for.

The answer depends on the species of grass to a degree. But most varieties of grass seed will definitely keep for 2-3 years, possibly up to 5. Cool-season varieties typically last longer than warm-season varieties.

Packets of grass seed should come with an expiration date on them which can be a helpful guide. But, it is just a guide!

You might be wondering, can you use expired grass seed?

And the answer, provided there are no obvious signs of spoilage, is definitely! You just might not have many seeds germinated successfully.

How to Tell if Grass Seed is Bad

If you’ve had a packet of seed sitting around somewhere for a few years and you’re not sure whether it’s any good, there’s actually a really simple way of finding out.

(First up, rule out any obvious signs of deterioration with a simple look and smell – if the seeds are visibly moldy, darkened in color or smell bad – chuck them.)

Assuming the seeds look and smell fine, all you need to do is take a small sample (may half a teaspoon) and try and get them to germinate.

An easy way to do this is to moisten a paper towel and fold the seeds into it so they are enclosed. Place the paper towel in a warm place for a few days and then come back to check.

If most of the seeds have started to germinate then you can be fairly sure that the rest of the packet is ok. If only 1 or 2 have germinated then you might have a pretty low strike rate with the rest of the packet. You can still use it, you’ll just need to use more than you usually would.

perfect green lawn in backyard

Before you go, have you ever wondered what to do with your grass clippings after mowing your lawn? I have a list of great ideas right here to save waste and put your lawn clippings to good use!

Summary

So, does grass seed go bad? The answer is yes, but it can happily last a good few years if stored correctly.

Remember, seeds are alive but dormant, so to keep them viable and capable of germinating they need to be kept in a cool, dark, dry place.

Hopefully, this article has answered all of your questions – if not, feel free to hit me with more below!

Andy Gibson

My name's Gibson. Andy Gibson. I like to think of myself as the Bond of the backyard, that is if yard work ever became sexy. I write about everything about indoor and outdoor gardening and the dread-it-but-still-need-to-do-it chores around the yard, like cleaning out the gutter guards.

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