I am very guilty of overbuying garden seeds. Whether I get a great deal on them or just get sucked in to all the beautiful images in the seed catalogs, I'm bound to end up with more than I can plant. I'm also guilty of saving too many seeds of my favorite heirloom varieties and then being tempted to save more again the next season. But is having too many seeds really a bad thing?
If you store your seeds properly, you can get a lot of life out of them. Many seeds are perfectly viable for as many as 5 years or longer if kept at the proper temperature and humidity level. There are seeds, though, that really are only viable for about a year after harvest and even those long-lived seeds will lose their germination potential over time. So, yes, seeds do actually expire.
But that's not to say the date on your seed packet is the end-all-be-all of when those can be planted. Seed suppliers are required to include certain information on seed packets when they sell them. Once of those is either the test germination date or the season the seeds were "packed" for. If you see a "packed for" year of 2019, it means those seeds were intended to be planted in that year. If you see a "germination date" of 10/2018, that means those seeds were collected and dried in 2018, they tested the germination rate in October of that year, and they were intended to be planted in 2019. This doesn't, however, mean the seeds expire after that. Like I said, how long your seeds last will be determined on their storage conditions and what kind of seed they are.
According to my alma mater, Oregon State University, the approximate time garden seeds are viable with proper storage is as follows:
Short-lived seeds (1–2 years): corn, onions, leeks, parsley, parsnip, chives, sage
Intermediate seeds (3–4 years): asparagus, beans, carrots, celery, peas, spinach, basil, oregano, cilantro, parsley, rosemary, thyme, dill
Long-lived seeds (4–5 years): beets and chard, cabbage family (Brussels sprouts, cauliflower, cabbage), turnips, radish, cucumbers and anything in the squash family; the nightshades - eggplant, peppers, tomatoes; lettuce, muskmelon or cantaloupe, watermelon
Why would seeds expire? Essentially, seeds are a little package that contains a baby plant and a boxed lunch. That little package has a hard exterior coating that protects the precious cargo inside. When we plant that seed, we want the exterior to degrade to allow moisture inside. That breaks down the boxed lunch into components the baby plant can use as energy to break out of the shell and start to grow. Anything that causes the degradation of that exterior before it's time for the plant to sprout is going to shorten the life of the baby plant inside. This degradation can be from temperatures that are too warm and too much moisture, i.e., humidity, but other factors come into play, too. Just like any living thing, age plays a role in a seeds ability to sprout and produce offspring (fruit or seed). You can keep your seeds at an optimum temperature and perfect humidity but, eventually, the seed will die. And even if they do sprout, the seedling may be weak and unlikely to produce.
So, yes, seeds do expire. But don't let that deter you from saving seeds or buying in bulk. Just be sure everything is properly labeled with dates and organize them so that you use the oldest seeds first. If you're not sure seeds are viable anymore, do this quick germination test to be sure and toss any that have a germination rate less than 70%.
What you'll need:
Seeds
Water
Marker
Plastic baggies
Paper towels
How to test:
- Moisten a paper towel with warm water. I soak it down, then squeeze most of the extra out. It needs to be moist but not dripping.
- Fold the paper towel in half and lay it flat on your work surface.
- Count out 10 seeds from the variety you're testing. Spread them out on one half of the paper towel so that they're not touching.
- Fold the paper towel over on the top of the seeds and press down lightly, essentially sealing the seeds in a paper towel envelope.
- Mark the variety of the seeds, the date you started the test, and the number of expected days to germination on the plastic bag.
- Slide the paper towel with the seeds inside the bag and seal it up. Place the bag in a warm place out of direct sun, checking every few days to be sure the towel (and seeds) stays moist, wetting when needed. A spray bottle works well for this.
- Check your results! After the expected number of germination days has passed, count the number of seeds that sprouted. This will give you your germination rate (i.e., 8 seeds sprouted means an 80% rate).
