This greatly depends on the seed (plant species) in question. Some seeds, like for pawpaw trees, must stay moist and experience winter chilling (called stratification) before they will break dormancy and germinate. If moisture-loving seeds dry out while in storage, or dry too much before they are put into storage (like in a fridge), they can die or the viability will decline drastically. Many of our native perennial, tree, and shrub seeds need stratification, though only some of them also need to stay moist.

Some seeds that can be stored dry, with or without a chilling period, might last for several years. Viability in all stored seed decreases the older the seeds get, but the speed of that decline will depend on the species and the conditions in which they were stored. A germination test, which uses a few of the stored seeds to see what percentage germinate, can help determine if a long-stored packet of seeds is worth sowing. One in a rare while, seeds surprise us, such as when news stories showcase a centuries-old seed found in some archeological artifact or a glaciated area which are actually able to still germinate.

Seeds sold by supply companies should have a date on the package for when they are intended for use (or at the very least, when they were harvested and stored). For example, a cucumber seed packet dated for 2024 is not ideal to use in 2025, as viability decreases, but that's not to say none will germinate, and it's worth experimenting with if you don't want it to go to waste. Retail garden centers (and presumably mail-order seed companies as well) will pull outdated seed from inventory once the season they are dated for is past, so only fresh seed is available when it's in season. (Local nurseries tend to restock seed packets around late winter or early spring, for example.)

Miri