Does Grass Seed Go Bad? (We Have The Answer)

Does Grass Seed Go Bad

We all have a dusty bag of grass seed slumped in the corner of our garage. If you are reseeding or overseeding your yard, you may wonder if you can still use that old grass seed. This article will explain how long grass seed lasts and what makes grass seed go bad. We will also give you a few tips on how to store it for the most extended shelf life.

Grass seed can go bad after 2-3 years and it slowly loses its potency over time. The germination rate after 2-5 years drops to 50%-60% for old grass seed. Store your grass seed in a cool and dry place so that it stays good and retains a high germination rate.  

This article will discuss the grass seed shelf life and how you can optimize it. Here’s a list of what we will cover:

  1. How grass seed goes bad
  2. What you can do to make grass seed last longer
  3. How to know if old grass seed is still usable

Here is a chart showing approximate germination rates after several years:

Grass Seed Age Germination Rate
1st Year 90-100 %
2nd Year 80-90%
3rd Year 70-80%
4th Year 60-70%
5th Year 50-60%
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Seed Germination Rate and Quality Grass Seed

The grass seed germination rate refers to the number of seeds that will sprout in a given season. Germination rate is impacted by a number of factors including harvesting conditions, production location, and the quality of the seed before you even purchase a bag. If the seeds were originally harvested in non-ideal conditions, the seeds’ germination rate will be substantially reduced, even if they were stored properly.

For best results, pay attention to both the germination rate and the tested rate when you’re shopping around for store-bought grass seed. These will most likely sit at about 80 percent or higher and you can expect your seed to germinate at this rate when it is used within the first year after packaging.

To ensure that you get a quality grass seed product, always purchase them from a reputable distributor. That way, you’ll always know that the seed was packaged and stored conferring with industry standards.

How To Tell if Grass Seed is Bad

You may wonder if your old bag of grass seed is still suitable for use. The best way to see if your grass seed is still good is to plant it. Follow the distributor’s guidelines for watering and fertilizer – see what happens. It’s impossible to determine with certainty how well your grass seed will do. However, here are a few steps to take to estimate your grass seeds viability:

  1. Determine your grass seeds age, and use the chart above to determine its germination potential. Grass seed tends to deteriorate about 10% of its original vitality every year after the first year.
  2. Inspect the grass seed for mold, fungus, or other apparent damage. If you look at your grass seed and notice anything obviously out of place, like holes in the bag or mold, you have likely lost most of that grass seed. However, there may be some grass seed within that will still germinate – but it will be lower than its original potential.
  3. How did you store the seed? If you took precautions and kept the seeds in a cool, dry place, you likely still have a higher percentage of viable seeds worth using in your yards. Storage conditions of grass seed strongly impacts longevity. (See our section below on how to store your grass seed)
  4. What type of grass seed do you have? With proper storage, most grass seeds report germination rates of 50% after three years; however, some grass seeds can go longer. Bentgrasses have reportedly had germination rates of 50% after ten years. That’s a long time. It’s worth looking into what type of grass seed you have.

All grass seeds will come with a “sell-by” date indicated on the label. However, this does not mean that the seeds are expired in the same way that milk may be. This just means that you will have a reduced germination rate.

How Does Grass Seed Go Bad?

It may be strange to think about, but grass seed is alive. Understanding this is the first step in learning how to maintain and store your grass seed. Like a plant, grass seed needs an optimal environment to maintain its vitality. Your grass seed is likely to go bad if exposed to the following elements:

  1. Extreme humidity and overheating may be the most deadly element to grass seed, and it will cause a drastic drop in the seed’s germination rate. Your germination rate is the percentage of seeds that produce grass. So, if you throw a handful of grass seeds damaged by heat and humidity, only 50% of those seeds might end up growing into grass.
  2. Extreme cold can hurt your grass seed; however, this will depend on the type of grass seed. Some seeds may tolerate freezing conditions better than others. Grass seed is full of living cells. If the cells freeze, they can burst and die.
  3. Pests, fungus, and molds can also harm stored grass seed. In general, you can thwart fungus and molds by keeping your seeds in a cool environment. When it comes to pests, you need to be concerned with birds, squirrels, and mice.

Eventually, even if you store your grass seed correctly, it will die. After the fifth year, you won’t see a high germination rate. There are some exceptions.

Grass seeds, such as bentgrasses, can maintain a germination rate of 50 percent for up to ten years. That’s a long time. If you want a grass with a high shelflife for, then bentgrasses are something to check out.

If you’re planning to redo your lawn, and are interested in different grass seeds, see this article on several different types of grass.

How to Make Grass Seed Last Longer in Storage

You’ve reseeded a lawn, and now you have a half bag of grass seed left over. Here are a few things you can do to optimize the lifespan of your grass seed.

  1. Storing in a cool and dry place is the most crucial step you can take to make your grass seed last. The optimal temperature is somewhere around 40-50 degrees Fahrenheit. If you have space, it’s possible to place your bag of grass seed in a refrigerator. Just be sure to have the temperature set to the proper levels. It’s best to avoid extreme temperatures, as grass seed cannot withstand exposure to rain or direct sunlight for extended periods of time.
  2. Place grass seed in a proper container. If you have a full bag of unopened grass seed, it’s best to leave it sealed. However, if you’ve already opened the bag, consider rolling the bag shut and clipping it closed with a clip. Some people have also had success with burlap and canvas bags. These bags let seeds to breathe and allow them to regulate their moisture needs.
  3. Use a desiccant or drying agent to help regulate moisture. Place an open box of baking soda within the storage containment to aid humidity control.

After you’ve stored your seeds properly, make sure that you date and label them accordingly. Also, before you use them again, always inspect for signs of moisture or mildew.

Here is a chart to help you remember proper grass seed storage:

Grass Seed Storage Guidelines
Environment Cool and Dry – off the Ground
Temperature From 40-50 Degrees Farenheight
Humidity Less than 50%
Storage Container Burlap or Cloth
Storage Agent Baking Soda to Control Moisture

Related Questions

Will grass seed last through the winter?

Yes, if stored in a cool and dry place, grass seed should last a winter. However, please don’t allow your grass seed to freeze, which will significantly reduce its germination rate.

How long does grass seed last without water?

Grass seed does not need water in storage. However, you don’t want to dry it out completely. For a planted lawn, the seeds can last pretty long if not exposed to moisture. But, if you’ve already begun watering, your seeds have likely started that germination process and will need regular water.

Will stepping on new grass kill it?

Heavy foot traffic will damage a developing lawn. However, stepping on developing grass from time to time will probably not be an issue.

Also, if you’re planting new grass, see our article on whether you can apply too much grass seed.

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Wrapping It Up

Grass seed can lose their vitality with time. How fast it spoils will depend on how it’s stored. It’s best to keep it in a cool and dry place off the ground and free from pests.

Remember, there is little harm in trying some old grass seed. If nothing else, use it to do some overseeding to thicken your lawn’s bare areas Don’t be afraid to reach out to the distributor of your specific grass seed as they will give you information tailored to your type of seed.

Grass seed is not incredibly expensive. When in doubt, don’t be afraid to pull the trigger and purchase some new product.

Your lawn will reward you with a golf course-like complexion!

Gideon Zielinski

Gideon is a writer and hobby woodworker. He enjoys working on projects small and large—everything from crafting boxes and benches, to replacing carpet and landscaping a yard.

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