Question: I just found a bag of grass seed I bought about 3 years ago. Is it still good?
Answer: Depending on the storage conditions, grass seed can remain viable from 1 to 7 years. It will last longest indoors under cool, dry conditions and much less in heat and humidity or in a tool shed where dramatic temperature swings occur.
Rather than waste time and effort sowing seeds that don’t come up, do a trial seeding first, easy to carry out indoors or out.
Sow 10 seeds on moist soil. If 7 or more seeds come up, germination is still excellent and you can proceed according to the recommended application rate. If 4 to 6 seeds pop up, double the rate. If 3 or fewer seeds are germinate, it would probably be better to buy fresh seeds.