By JASON GRAVES
K-State Research and Extension Central District Horticulturist
As seed catalogs start to fill my mailbox, I’m reminded of the stash of leftover garden seeds I’ve saved from past seasons. Like many gardeners, I wonder: Should I plant these older seeds or invest in fresh ones for the upcoming growing season? The answer depends on two key factors: how the seeds have been stored and whether they are still viable.
Seed storage
Seed longevity depends heavily on storage conditions. It is best to place packets of seed in an airtight container for better protection. Always keep seed containers labeled with the date of storage for future reference.
The three biggest enemies of seed viability are moisture (humidity), heat, and light. To maximize seed longevity, seeds should be stored in a cool, dry location-ideally below 50 degrees and with less than 60% humidity. A refrigerator is an excellent option as long as seeds are kept in a tightly sealed and airtight container to protect against moisture. Purchased seed can also be stored in an airtight container in the freezer to extend its viability even longer.
If cold storage isn’t an option, the next best thing is to find a place in the home with a consistent temperature such as a shelf in the basement, an interior closet, or under a bed (away from air vents).
Testing seed viability
If your seed is more than a year or two old or storage conditions haven’t been ideal and you also have plenty of leftover seed, testing seed viability before planting is a wise step. Here’s how to test seed viability:
Take 10 seeds from your leftover packet.
Place them on a damp paper towel and cover them with another moist towel.
Roll up the towels and put them in a plastic bag with a few small air holes. Place the bag in a warm spot, such as the top of your refrigerator.
Check after a week and count and remove any sprouted seeds. Continue monitoring for another week to calculate your germination rate.
A germination rate of 70% or higher (7 out of 10 seeds have sprouted) means that seeds are still usable, but you may want to sow more densely. If the germination rate is 50% or less, it is probably best to purchase new seeds.
Length of seed life
Seed longevity varies by plant type, even when stored correctly:
4–5 years: Crucifers (like broccoli, cabbage, and kale), lettuce, tomatoes, cucumbers, eggplant, and melons.
2–3 years: Carrots, beets, chard, corn, okra, pepper, peas, and spinach.
1–2 years: Parsnips, onions, and parsley are among the shortest-lived seeds.
When to buy new seeds
In summary, if your garden seeds have been stored in less-than-ideal conditions or fail the germination test, it’s a good idea to purchase some fresh seeds for 2025.
A practical strategy for many gardeners can be to combine leftover seeds that have been stored properly or pass the viability test with a few new selections from your favorite seed catalogs. This approach can help save money and still allow room to experiment with new garden varieties.
To learn more about resources made available by K-State Research and Extension Central District and to find out more tips from Jason Graves, check out their website here.