How to Tell If Old Seeds Are Still Good Before Planting Them

How Long Do Seeds Last?

Store-bought seeds of any sort generally stay fresh for at least a year after purchase. But the actual germination rates of older seeds will depend on the type of seed and how the seeds were stored.

Unless the seeds were stored in a damp or otherwise unsuitable location, seed germination rates don’t decline all at once. Instead, the actual germination rates of seeds begin to decline after the “best by” or “use by” date that’s listed on the seed packaging. After this date, some seeds will usually still be viable, but you may need to plant more of them to get the same germination results.

If your seed packets don’t list a “use by” date, here's how long common seed varieties usually stay fresh with proper storage.

Annual flower seeds usually last for 1 to 3 years.
Perennial flower seeds maintain good germination rates for 2 to 4 years.
Alliums, lettuce, parsley, and parsnip seeds expire faster than most and should be replaced after 1 to 2 years in storage.
Leafy greens and root veggies remain viable for 1 to 4 years, depending on the variety.
Nightshades and Brassicas sprout well for 3 to 5 years after purchase.
Cucumbers and other plants in the Cucurbit family stay fresh the longest. These seeds can last up to 10 years.

How to Tell If Old Seeds Will Grow

In an ideal world, every seed packet is labeled with a “best by” date. However, some packets don’t have dates listed and homegrown seeds may not be dated at all. If you have seeds that you’re not sure are viable or not, performing a simple seed germination test will let you know if those seeds are worth planting and save you the trouble of sowing your garden with seeds that won't sprout.

Here are 3 basic seed germination tests that you can use on different sorts of seeds.

Paper Towel Test

The most basic seed germination test, the paper towel test works on most common seeds, including most annuals, veggies, and herbs.

Step 1: Dampen a Paper Towel

To start, wet a paper towel so it’s about as damp as a wrung-out sponge and lay the paper towel flat on your work surface.

Step 2: Count Out 20 Seeds

Count out 20 seeds from a seed packet you’d like to test the viability of and lay the seeds out in a single, even layer on the paper towel.

Step 3: Create Your “Germination Station”

Fold the paper towel in half, slip it into a ziptop baggie, and seal the baggie shut. Alternatively, you can lay the paper towel in the base of a clear food storage container and then close the container tight. When you're done, write the seed variety and date on the outside of the baggie or container.

Step 4: Add Light and Warmth

Move the seeds into a bright location that’s relatively warm; 70°F is ideal, but slightly cooler temperatures are okay for most seeds. Leave the seeds in place for 7 to 10 days or as long as it typically takes the specific seed variety to sprout. During this time, check the seeds regularly and re-dampen the paper towel if it starts to get too dry.

Step 5: Assess the Results

Once the seeds have had enough time to germinate, open your “germination station,” and count the number of seeds that sprouted. Divide this number by 20 (or the number of seeds you planted) and then multiply this number by 100 to get the germination rate for the seeds.

If the germination rate is above 80%, the seeds are still sprouting well.

If the germination rate is below 50%, it’s time to replace the seeds with fresh ones.

If the germination rate is between 50 and 80%, the seeds may still be worth planting but it’s wise to “overseed” or plant more seeds than you think you'll need. This will ensure enough seeds actually sprout.

Nasturtiums, gourds, and some other larger seeds sprout better if you scarify the seed coats before planting or germinating. You can do this by lightly running the seed coat over fine-grit sandpaper a few times.

Soil Test

Peanuts and some other “stubborn” seeds don’t germinate well on paper towels and aren’t well-suited for the paper towel germination method. If you want to test the viability of these seeds, fill a pot or seedling tray with damp seed starting mix and then plant 20 seeds at the depth listed on the seed packets. Once the seeds have had enough time to germinate for the specific seed variety, calculate the seed germination rate using the steps listed above.

Cold Stratification Test

Lavender, milkweed, and many wildflower seeds that are native to cold areas need to be cold stratified to sprout well and performing a germination test without this key step may skew your results. If you have seeds that require cold stratification, place the seeds on a damp paper towel in a ziptop baggie in your fridge for about 4 weeks, then remove the seeds from the fridge, count out 20 seeds and place them on a fresh, damp paper towel. Then, follow the paper towel test tips above to determine how well the seeds sprout.