Now that the new growing season is upon us, just how long do seeds last and how can you know if they’re too old for germination and when you should replace them? If you are into seed buying right now, read on.

Even though I’ve started buying a few new vegetable seeds of varieties I’ve never tried for this coming season, I’m just going through all my existing seeds to see what might be getting old, what seeds are already too old, I what I should throw out and what I need to replace.

Here’s how to decide what condition your seeds are in to help determine their viability. On most package of seeds, there is a date on them to help you know the age of your seeds and whether they are viable. If there is not a date, I write down the year I bought them on the seed envelope and if I get the seeds from a friend, I ask how old they are and write that date down. I’ve bought seeds with no date and didn’t write the date I bought them which then can become a problem. But there is something you can do to help determine if they are too old.

I take 10 seeds of one variety and put them in a damp paper towel folded up and put it in a zipped plastic baggie. Then I put them someplace warm like the top of your refrigerator to help them germinate. Check for germination in a few days up to 10 days. If you have 8 germinate, then you have a 80% germination rate which is excellent. If you have say 5 seeds germinate then you have 50% germination rate. If I find I have less than 50%, I don’t necessarily throw them out but maybe double them when you plant the seeds. If I have 30% or less, I usually toss them. The only problem with doubling up the seeds is if you are on a timetable where you need to get them in the garden by a date you picked and they don’t germinate, you may be replanting the seeds without enough time to start over and get them in the garden in time.

Having said that, I still hold the NM State record for a giant green pumpkin that I grew from a seed that was 9 years old but it was the only seed I had for a green pumpkin and it turned out to be a huge pumpkin at 340 lbs. And I’ve heard of seeds found in Egyptian tombs that germinated.

How you store them has an effect on seed germination. Freezing extends the life of the seed, so that’s an option but you must make sure the seed is really dry. I put one of those little packages of desiccant (you find in your vitamin bottles) inside your freezer baggie. I save those and put one in with the seeds. You must keep the seeds from getting moldy. You don’t have to freeze your seeds. Sometimes, I just let them stay in my greenhouse during winter  in jars but be sure mice can’t get to them. But mostly, I just keep the seeds in their envelopes inside the house in a nice dry place. And you may have heard of the Svalbard vault where they store thousand varieties of seeds in sub-zero environment to make sure they don’t go extinct. Did you know we’ve lost 90% of vegetable varieties through the years by people not keeping the varieties going?

Here is a seed lifespan chart. This is a guide only and some seeds can last longer if you take care of your saved seeds.

So now is a good time to check out your seed supplies and get your replacements before the season starts.