ShelfYears

Does grass seed expire?

Yes, quietly — Scotts gives a well-stored bag 2 to 3 years, and Jonathan Green puts a fresh bag near a 90% germination rate and one a couple of years old at 70% or lower.

Updated

Grass seed
Sealed
2–3 years
Opened
Within 1 year
LOSS OF VIABILITY
Degraded performance

Sealed: 2–3 years Tier 1

Scotts' answer to how long seed keeps is 2 to 3 years stored in a cool, dry place, with the germination rate falling the whole time. Jonathan Green's window starts a year earlier and lands in the same place: 1 to 3 years on average, up to 3 years for a sealed bag kept cool, dry and out of direct sun.

By manufacturer — the disagreement is information
Brand Sealed window
Scotts 2–3 years
Jonathan Green 1–3 years

After opening: Within 1 year Tier 1

Both makers land on the same number for an opened bag, and it is much shorter than the sealed one. Jonathan Green's line is to use it within a year for the best results; Scotts' is to use fresh product and try to sow it within a year. An opened bag is an open invitation to the humidity in a shed, and moisture is what ends a seed.

How to tell it's gone off

  • Clumped or caked seed, or a bag that feels damp — moisture is the thing that ends germination.
  • A musty or mildewed smell from the open bag.
  • Where it has been kept: a hot, bright shed shelf ages seed faster than the calendar does, and both makers ask for cool, dry and dark.
  • Age itself. Jonathan Green puts a fresh bag near a 90% germination rate and a bag a couple of years old at 70% or lower — and nothing in the seed's appearance shows that.

If you use it anyway

Degraded performance

Old grass seed is the textbook version of degraded performance: it still sprouts, just less of it. Jonathan Green's numbers are a fresh bag near 90% germination and a two-year-old bag at 70% or lower, and Scotts caps a well-stored bag at 2 to 3 years with the rate falling throughout. Nothing is damaged and nothing is hazardous — you do the same amount of work and get a thinner, patchier lawn.

Why it goes off — LOSS OF VIABILITY

Grass seed is alive, and every month in storage some fraction of it stops being able to sprout. Warmth and humidity speed that up — which is why both makers frame storage as cool, dry and dark rather than as a date. Nothing about the seed's appearance changes as this happens, which is what makes old seed such a reliable disappointment.

Every page here commits to one of four states — Harmless · Degraded performance · Equipment damage · Safety issue. How the verdicts work.

How to store it

Both makers ask for the same four things: cool, dry, sealed and dark. Jonathan Green's terms are an airtight container at cool, stable temperatures away from direct sunlight and UV; Scotts' is simply a cool, dry place. The bag's enemy is humidity, not time.

Sources