Most garden seeds stay good for two to five years, but the range is wide. Onion and parsnip seed can lose most of its vigor after a single year, while cucumber, lettuce and radish seed often sprouts well five or six years later. How you store seed matters as much as which crop it is. This guide gives you a crop-by-crop chart, explains what "viable" really means, and shows you how to test old seed in about a week before you trust it with a garden bed.
Seed viability chart: how many years seeds last
These are typical storage lives for seed kept cool, dark and dry, from Purdue University Extension, based on Knott's Handbook for Vegetable Growers. Seed kept warm or humid can fall short of these numbers. Seed kept in better conditions often beats them.
| Crop | Expected years | Crop | Expected years |
|---|---|---|---|
| Onion | 1 | Kohlrabi | 3 |
| Parsnip | 1 | Carrot | 4 |
| Okra | 2 | Pumpkin | 4 |
| Pepper | 2 | Squash | 4 |
| Bean | 3 | Tomato | 4 |
| Sweet corn | 3 | Turnip | 4 |
| Pea | 3 | Watermelon | 4 |
| Spinach | 3 | Cucumber | 5 |
| Muskmelon (cantaloupe) | 5 | ||
| Radish | 5 | ||
| Lettuce | 6 |
For flowers, see our flower seed viability chart. As a quick guide from the same Purdue list, zinnia, calendula and nasturtium seed keeps about 5 years, marigold about 2, and aster, pansy and phlox about 1.
If a crop isn't listed, don't guess. Run the germination test below before planting.
What "viable" means (and why old seed isn't all-or-nothing)
A seed is viable if it is still alive and able to sprout. Seeds don't expire on a set date. A packet loses germination a little at a time: a lot that sprouted at 90% when it was fresh might sprout at 70% a few years later, then 40%, then hardly at all. Older seed also tends to sprout more slowly and produce weaker seedlings.
That means a packet past its "expected years" is often still usable. You just sow more thickly to make up for the seeds that won't come up. The test below tells you how much more.
Do heirloom seeds last longer than hybrid seeds?
No. Heirloom, open-pollinated and hybrid seeds of the same crop age at about the same rate. What heirloom seed gives you is the ability to replace your supply: seed saved from open-pollinated plants grows true to type, so a seed bank of heirlooms can be renewed from your own garden. Our article on what heirloom seeds are explains why.
How to test old seeds: the 10-seed paper towel test
- Count out 10 seeds from the packet.
- Dampen a paper towel so it's moist but not dripping. Spread the seeds on half of it and fold the other half over them.
- Slide the towel into a zip bag or container, leave it slightly open for air, and label it with the crop and date.
- Keep it somewhere warm, around 70°F to 80°F. Peppers and other warm-season crops sprout faster at the warm end. The top of a refrigerator works for many people.
- Check every day or two and keep the towel moist. Count a seed as sprouted when a small root pokes out.
- After 7 to 10 days (up to 2 to 3 weeks for slow crops like peppers and parsley), count the sprouts.
Reading the result: each sprouted seed is 10%. If 8 of 10 sprout, sow as normal. If 5 of 10 sprout, sow about twice as thickly. If 2 or fewer sprout, replace the seed. You can also plant the sprouted seeds from the test; handle them gently by the seed, not the root.
Skip the "float test." Dropping seeds in water to see which sink is a popular tip, but it isn't reliable. Good seeds can float because of air trapped in the seed coat, and dead seeds can sink.
How to make seeds last as long as possible
Heat and moisture are what age seed. The cooler and drier you keep it, the longer it lasts. In short:
- Cool: a closet or basement shelf is better than a garage, shed or kitchen cupboard by the stove. The refrigerator works well for seed in an airtight container.
- Dry: keep packets sealed. A packet of silica gel or a layer of dry rice in the container soaks up stray moisture.
- Dark: keep seed out of sunlight, which heats the packet.
- Steady: avoid places that swing between hot and cold.
For containers, the fridge and freezer, oxygen absorbers and how to store a seed bank for many years, see our full guide on how to store seeds long-term.
Stocking up? Plan around the short-lived crops
If you are building a seed supply for several seasons, the chart tells you what to refresh first. Onion, parsnip, okra and pepper seed should be replaced or tested every year or two. Tomato, squash, cucumber, melon, lettuce and radish seed can be bought less often.
Our Survival Seed Vault Kit packs 35 heirloom vegetable, fruit and herb varieties in individual labeled packets inside a resealable Mylar bag, which makes it easy to keep the whole set cool and dry and to rotate it. For a larger supply, the heirloom seed assortments include 70- to 140-packet kits. Our guide to comparing survival seed vault kits explains what to look for.
Common questions
Do seeds expire?
Not on a fixed date. They lose germination gradually. A "packed for" year on a seed packet tells you when the seed was packed, not when it stops working. Test older packets before relying on them.
Can I plant 5-year-old seeds?
Often, yes, especially cucumber, lettuce, radish and melon seed. For short-lived crops like onion and pepper, run the 10-seed test first and expect to sow more thickly.
Is it worth freezing seeds?
Seed banks freeze seed after drying it to a very low moisture level. At home, seed that isn't fully dry can be damaged by freezing, so Purdue Extension recommends the refrigerator instead. Our seed storage guide covers this in more detail.
Why did my old seeds sprout but grow poorly?
Aging seed loses vigor before it stops sprouting entirely. Seedlings from old seed can be slower and weaker. Give them warmth, good light and a little extra time, and sow a few more than you need.
Reviewed by Ryan, owner of Gardeners Basics, an heirloom seed company that ships from Spanish Fork, Utah.
