This season I’ve definitely learned that parsnip seeds don’t keep for more than the year they’re sold for. I had a packet (opened) left over from last year and sowed some of them, alongside some from a brand new packet. The new ones popped up fine. The old ones didn’t produce a single shoot. And they’d been properly stored in a cold, dark, dry place and all that. Note to self: buy new parsnip seeds each year. Or of course, try letting one of the parsnips grow too long and pick the seeds from its flowers.