How Long Can You Store Unopened Grass Seed?

The longer grass seed is stored, the more its vigor is compromised.

Germination rates and viability of grass seed decrease over time. Properly stored, grass seed can retain most of its planting value for up to a year. Keeping it any longer than that is not advised.

Storage Conditions

Grass seed should not be stored in locations with excess temperature or humidity.

Grass seeds are hygroscopic, meaning that they absorb moisture from the air, so a dry environment is essential for storage. They require a combined temperature and humidity equal to or less than 100; for example: 70 degrees F with 30 percent humidity or 40 degrees F with 55 percent humidity. Any value greater than 100 will greatly diminish the seed's viability, according to Penn State Cooperative Extension.

Seed That Shouldn't Be Stored

Moist grass seed should not be stored.

Some grass seed should not be stored to begin with. Any grass seed that has been exposed to moisture should be used or disposed of. Nor should you store any seeds that are cracked or otherwise bruised.

Federal Labeling

Make sure that you know how long your grass seed has been stored.

You need to know exactly how old your bag of grass seed is before you consider storing it. The Federal Seed Act of 1936 requires all seed to be labeled with the date packed, germination rate and lot number, among other identifying information. If you cannot verify how old your seed is, do not expect great results.

References

• Oregon State University; Maintaining Grass Seed Viability in Storage; Sabry Elias et al.
• The Ohio State University Extension: Fact Sheet; Lawn Grass Cultivar Selection; William E. Pound and John R. Street; 2002
• Purdue University; Turfgrass Selection and Identification: Turfgrass Types and Growth
• Penn State Cooperative Extension; Maintaining Seed Viability and Vigor