How Long Does Grass Seed Last? A Guide to Seed Longevity
When you buy a bag of grass seed, it’s easy to assume it will stay good for years if you don’t use it all right away. But like any living product, grass seed has a shelf life. Understanding how long grass seed lasts—and how to store it properly—can mean the difference between a lush lawn and wasted money.
Does Grass Seed Expire?
Yes. Grass seed doesn’t “expire” like milk, but its germination rate drops over time. Fresh seed typically has a high germination percentage (often above 80%), meaning most seeds will sprout under the right conditions. As seed ages, fewer and fewer will germinate.
Most grass seed remains viable for 18 to 24 months when stored properly. After that, the germination rate steadily declines. By year three, you may only get half the results you would from new seed.
Factors That Affect Grass Seed Longevity
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Storage Conditions
- Seed should be kept in a cool, dry place.
- High humidity or heat can trigger mold, rot, or premature aging.
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Packaging
- Unopened bags last longer than open ones. Once a bag is opened, it’s more exposed to moisture and pests.
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Seed Type
- Some grass types, like perennial ryegrass, tend to lose viability faster than fescues or bluegrasses.
How to Store Grass Seed for Maximum Life
If you’ve got leftover seed, don’t just toss it in the garage and forget it. To preserve seed quality:
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Keep it in its original bag, sealed tightly.
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Store indoors, ideally in a dry basement or closet.
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Use an airtight container or heavy-duty plastic bin if possible.
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Avoid storing on concrete floors where moisture can seep up.
How to Tell if Old Seed Is Still Good
Not sure if that bag in your shed is still worth using? You can test it:
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Place about 10 seeds on a damp paper towel.
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Fold it up and seal it in a plastic bag.
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Leave it in a warm spot for 7–10 days.
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Count how many seeds sprout.
If 7 or 8 out of 10 sprout, your seed is still in good shape. If only 2 or 3 do, it’s time for a fresh bag.
Grass seed doesn’t last forever, but with proper storage you can usually rely on it for up to two years. Using fresh seed ensures the highest germination rate and gives your lawn the strong, thick start it needs. If you’re serious about your lawn, investing in fresh seed is always the safer bet.
