How to Know If Your Grass Seed Has Gone Bad

<p>DonNichols / Getty Images</p>

DonNichols / Getty Images

Unless you’re reseeding your entire lawn, it’s unlikely that you will use an entire bag of grass seed. If you’re just reseeding a few patches, there will be some leftover. Grass seed can be expensive and does not usually come in small quantities, leaving you with plenty to use down the road—but does grass seed go bad?

Below, we tell you if grass seed goes bad, how to tell if it’s turned, and how to properly store it to keep it in its best shape for as long as possible.

Does Grass Seed Go Bad?

Yes, grass seed does go bad, but not like a fruit or vegetable that becomes uneatable when it rots; grass seed just becomes less viable as it ages. The germination rate per volume of seed drops, meaning you need to use more seed to cover the area.

Factors That Affect Grass Seed Longevity

Unless you store your seed in a scientifically certified seed bank, it will eventually deteriorate. Some of the factors that make grass seed go bad faster are avoidable, and others are not.

The biggest factor affecting your grass seed is time. Grass seed will generally last two the three years before the germination rate reduces. Heat, light, moisture, and airflow will shorten grass seed’s viable lifespan.

To elongate your grass seed’s shelf life, avoid storing it in warm, bright, moist, and airy conditions.

Signs Your Grass Seed Is Expired

If you have old grass seed and you need to re-seed an area and you're unsure if your seed is viable, here are a few tests to tell if it is still good:

  • Do the float test: Put a small handful of grass seeds in a glass or bowl of water and see how many float. If more than 80% float, then most likely your seed is good.

  • Do a germination test: This method is tedious but will be the most accurate for the average gardener. Count out 100 seeds and plant them on a paper plate covered with moist soil. Cover the plate with plastic wrap and keep it in a sunny place. Moisten the soil every day or two (a spray bottle works well). After a week, count the number of grass sprouts you have. If you have 80 or more, your grass is viable. You can do the same thing with a paper towel and water on a windowsill in a less controlled method. (You have to count the seeds because you won’t see the ones that didn’t sprout—they’ll be buried in the soil.)

  • Physical inspection: Look closely at the seed. Does it feel light; look uniform in color; smell fresh, and not musty? Viable seeds will have a firm, whole appearance and be heavier than seeds that have lost their viability.


Even though you think you’re saving money by using old grass seed that has lost its viability, you have to use a lot more seed and there’s a greater failure rate—which is a waste of your time. Using fresh grass seed is often the way to go.

How to Correctly Store Grass Seed

The most important thing you can do to store your grass seed correctly is adequately reseal the bag. Use multiple chip clips or office clips. Store the seed in the vegetable crisper drawer of the refrigerator, if you happen to have an extra refrigerator in the garage or basement. (The fridge is a great place to store seeds for extended storage.) With no fridge available, your next best option for storing grass seed is an empty insulated cooler, especially if you are in a cooler climate, or a resealable storage bag.

Frequently Asked Questions

Is it OK to use really old grass seed?

It is okay to use really old grass seed, but after two to three years the amount of seeds that are still viable will be greatly reduced. This means that even if you store your grass seed perfectly in a cool, dry place, you will still need to use more seed to get sufficient coverage for a lawn.

How long will a bag of unopened grass seed last before it goes bad?

For an unopened bag of grass seed, there will be a noticeable decline in germination percentages from the seeds after two to three years, even if the seed was stored in a cool, dry place.

How long will a bag of opened grass seed last before it goes bad?

Store a bag of grass seed in a cool, dry place—correctly sealed—and it will last two to three years before you notice any diminishing results in germination percentages.

Read the original article on The Spruce.