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How Long Will Grass Seed Keep For?
In general, grass seed will keep for up to 5 years if fresh to begin with. The biggest influence on germination is how well it is stored, not the age.
How to Store Grass Seed for Maximum Freshness
High temperatures, humidity, light and sweating are the biggest seed killers.
Storing in a cool, dark area of a basement or garage is probably the best place, though basements can be humid. Away from light is easy, so the main aim is to keep the grass seed dry and cool. Garden sheds get very hot, and this can easily ruin your seed. If you have an old fridge and not much seed to store, this would be perfect.
Store in a Breathable Bag
Our 5kg and 10kg bags are made of polypropylene which is a breathable plastic. Do not put this in a bin bag or other container that does not breath. Seed contains moisture and will sweat in warm temperatures rotting the seed very quickly.
Our small bags are polythene with air holes. Add a lot more holes if you’re going to store for a period of time. This can be done with a large pin or sowing needle.
Rate of Deterioration of Grass Seed
Expect any seed to deteriorate by between 10% and 30% a year. Kept well, seed may deteriorate by only 10% a year so can last for 5 years. Just increase the sowing rate by 10% for every year you’ve kept it.
Seed in the shed or not kept in optimal conditions may deteriorate between 20% and 30% a year so isn’t going to be much good after 2 or 3 years. If your seed experiences a heat wave (a few days over 30°) then test it before using.
How to Tell Seed Freshness
When shopping go to a trusted supplier who you expect to have a high turnover so you know it hasn’t been kept long. Then read the reviews.
Any bag of 5kg or more should have a DEFRA green label stitched into it. This will have a bagging date on it. Seed you buy today will be from last year’s harvest so a bagging date of last year or the current year is what you’re aiming for. All Lawnsmith seed will be labelled the previous year or the current year and is rarely in our warehouse for more than 3 months.
It is not possible to tell how well seed will germinate by looking at it, so if it’s been kept for more than a season test it before using. It just requires a little planning and forethought.