ShelfYears

Does weed killer expire?

Barely — Roundup prints a shelf life of 8 years for its Super Concentrate stored undiluted in the original container, which makes it one of the longest-lived things on the shed shelf.

Updated

Weed killer (glyphosate)
Sealed
4–8 years
Opened
2–8 years
FORMULATION SEPARATION
Degraded performance

Sealed: 4–8 years Tier 1

Roundup publishes the figure on the product page itself: 8 years when stored undiluted in the original container. The ready-to-use bottles get a shorter number from the same company — 4 years in their original container — because a ready-to-use product is mostly water and the dilution is already done.

By manufacturer — the disagreement is information
Brand Sealed window
Roundup Super Concentrate 8 years
Roundup Ready-To-Use 4 years

After opening: 2–8 years Tier 3

Roundup's 8-year figure is written against the container, not the seal — a part-used jug that goes back on the shelf capped and undiluted is still "undiluted in original container". What pulls the number down is headroom and handling: Purdue's storage guidance treats a package that has been previously opened as a reason to look at the liquid before trusting it, and puts the industry's design window at two to three years for the general case.

How to tell it's gone off

  • A hard-packed sediment on the bottom that stays there after the closed jug is gently inverted several times.
  • Separated layers that stay separate.
  • An odor or a colour that has drifted from what a fresh jug looks and smells like.
  • Crystals in the liquid — the signature of a jug that has been through a freeze in an unheated shed.

If you use it anyway

Degraded performance

Old glyphosate concentrate is a wasted-Saturday problem, not a hazard one. Roundup's own number is 8 years for undiluted product in its original container, and Purdue's storage literature says active ingredients are quite stable in a sealed concentrate. What fails first is the formulation: a jug that has separated or thrown a hard sediment sprays weak and patchy. The weeds live. Nothing else happens.

Why it goes off — FORMULATION SEPARATION

Glyphosate concentrate is chemically stable in a closed jug — Purdue's blunt summary is that active ingredients are quite stable in the concentrated formula sealed in the container. What ages is the formulation around it: the surfactants and carriers that keep everything in one uniform liquid. Let a jug freeze and the active can crystallize, settle, and refuse to go back into suspension when it thaws.

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

How to store it

Roundup's own condition is the storage rule: undiluted, in the original container, capped. The label caution on the same page settles what it may never sit in — do not store this product or its spray solutions in galvanized steel or unlined steel containers or spray tanks. Purdue adds the one a garage actually threatens: keep it above freezing, because a freeze-thaw cycle can drop the active ingredient out of suspension for good.

Never place unused product down any indoor or outdoor drain.

Sources