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

Written by Andy Gibson in Grass & Grass Seed Last Updated on

Do you have a section of your shed or garage you rarely venture into?

The deepest, darkest corner where shelves are stacked high with all kinds of forgotten, dust-covered products, and the spiders thrive undisturbed in the gloom?

Well, one day, you might decide to clear it all out.

And it’s there you find a half-empty, opened bag of 10-year-old grass seed.

BONUS! What a discovery!

But STOP RIGHT THERE!

Before you start chucking it around the bare spots on your lawn – can you actually still use it?

Do grass seeds go bad or expire?

Let’s find out!

Grass Seed Shelf Life – Too Long, Didn’t Read

I get it. You’re super keen to throw the bag of grass seeds straight into the spreader and hit the lawn.

With that in mind, here’s a brief summary of this article if you’re impatient and want to get to work:

  • 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.

Of course, I’ll explore each of these points in more detail further on in the article, so I highly recommend you stick around for some top tips and expert advice on using and storing grass seed.

It will certainly help you when it comes to cleaning and reorganizing that forgotten section in your garage.

bag of lawn seed on grass

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.

man holding grass seed in hand

How Long is Grass Seed Good For?

The length of time grass seed remains usable will depend on a number of factors.

This includes proper storage (more on this below). As well as the type of species.

Most varieties of grass seed should keep for one to two years, with a maximum shelf life of up to five years – given optimum conditions.

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

But, it is just a guide! There won’t be a definitive date that the seed suddenly packs in!

With that in mind, you might be wondering if you can use expired grass seed?

Providing there are not any obvious signs of spoilage – such as mold – you can certainly try laying down grass seed that’s well past its best.

There’s no harm in giving it a go – and it sure beats simply throwing it out.

Just be aware that the ratio of seeds that actually germinate might not be anywhere near as high as if you were to use a fresh bag.

As a rule of thumb, it is estimated that this germination rate will deteriorate between 10 and 20 percent each year the bag is open and in storage.

Compare this with an 80 to 90 percent success rate within the first year of opening a bag, and you have your answer.

tow behind spreader attached to riding lawnmower

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.

Once you’ve established whether you can use your dusty old bag of grass seed, you might need a refresher on how and when to properly lay it down.

Check out this article on how to grow a healthy lawn, which has some expert advice on overseeding and lawn repair.

And once you have a lush, green carpet in your yard, you’ll also want to know how best to cut it. Read these 14 essential mowing tips and get it done right.

private house backyard lawn

How to Properly Store Grass Seed

You may have used your old grass seed, or you may have thrown it out.

Either way, it’s important to understand the optimum storing conditions for any bags you might happen to pick up in the future.

So you avoid any unnecessary waste, and maximize your chances of germination success.

Contrary to what you might think, your garden shed or garage is not actually the ideal location in which to store seeds.

These places are often not insulated, and will be exposed to a wide range of temperatures that a bag of seeds isn’t exactly going to enjoy.

And depending on the age and quality of your shed or garage, they might be prone to a little leakage – particularly during heavy rain or lengthy spells of wet weather.

This will expose your seeds to excess dampness and moisture, which could easily result in spoilage.

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.

So, what’s the answer?

The best (and most practical) place to store grass seeds is in a cupboard indoors. Somewhere the temperature is going to stay cool all year round.

A basement is ideal, and a dark cupboard in that basement is even better. If you haven’t already, you might want to install a dehumidifier to keep moisture regulated.

If you can, decant an open bag of seeds into sealed, opaque containers. That will take care of the light and moisture issue.

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!

a green lawn in backyard

FAQs

Is 10-year-old grass seed still good?

Yes and no. Providing there’s no obvious signs of spoilage, you could still try and use a bag of seeds that is 10 or more years old.

Just remember that the rate of germination falls by 10 to 20 percent every year since it was first opened, so there’s a good chance you won’t have much success with something that’s sat on the shelf this long.

Can I use 5-year-old grass seed?

Yes, again, bearing in mind the germination rate guidelines.

The older the bag of seeds, the more product you will need to disperse to stand a chance of good coverage.

How do you know if grass seed is still good?

Try this neat trick:

Put a small handful of seeds into a glass of water or other such container, and let them sit for 15 to 20 minutes.

If the seeds float – they have most likely spoiled.

If they sink, you’re good to go.

Aside from this, you could always try germinating a few seeds on damp kitchen paper to see if they are still viable. And don’t forget to check for any obvious signs or smells of spoilage.

Does bagged grass seed go bad?

Providing grass seed is stored in a cool, dry, and dark place with regulated temperature, there’s no reason why it can’t keep for up to five years.

All grass seed will “go bad” eventually – bagged or otherwise.

How long is Scotts grass seed good for?

Scotts is one of the most popular companies for grass seed and fertilizer. They say that their seed can last between two and three years – which is straight from the horse’s mouth.

When in doubt, regardless of which brand you’re using, always be sure to check the label.

Can grass reseed itself?

Yes. Like most plants, if you let them “go to seed,” they will produce seed heads that will eventually be distributed wherever the grass is growing.

However, this course of action is not recommended, as you’d need to let your grass grow for a few months, which has many more detrimental effects than simply being difficult to mow.

Allowing grass to reseed isn’t going to be anywhere near as effective or practical than manually overseeding with a fresh batch of product.

This article explains how grass can spread in more detail, with some tips on how to make it do so more effectively.

Will grass grow if you just throw it on the ground?

Yes and no.

It depends on where you’re throwing it, how much sunlight, water, and other nutrients it’s going to get, and how much stress and traffic it’s going to be under.

Grass seed, no matter how fresh, still needs a fair amount of nurturing in order for it to grow into a thick, healthy, luscious green lawn.

Does grass seed go bad if it’s not watered?

Yes.

Improper watering (either too much or too little) can cause your newly sown grass seeds to fail and go bad.

Once planted, it will need to be watered at least once daily, but no more than three to four inches per week. Five to ten minutes morning and evening.

This will slowly taper off as the seeds begin to germinate.

For more advice, including a step-by-step guide to overseeding and watering, check out the video below.

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 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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