"Some seeds can live for a long time before germination, while others can only survive for a short period after dispersal before they die."[1]

I wasn't suggesting all seeds would fail to germinate after two years, just that some would, and that change would be noticeable in the fossil record.

1: https://en.wikipedia.org/wiki/Seed#Germination

Old seeds had much higher germination rate according to the linked wikipedia article. In addition, cold storage increases the life of seeds. I doubt you would see much of anything in the fossil record.