Do Seeds Expire? How to Know If Yours Are OK to Plant

If you're an avid gardener, chances are you've stumbled across old seed packets you never got around to planting. If you're ready to get them in the ground now, you may be wondering if they're still viable. Over time, seeds can lose their ability to produce strong seedlings, but do they ever truly expire? We tapped gardening experts, who explain whether or not seeds go bad and how to know if yours will still germinate.

Do Seeds Go Bad?

Seeds will eventually "go bad" with age, which essentially means their viability (the seed's ability to produce a vigorous seedling) fades, and they will no longer germinate. "If not planted, over time their viability decreases due to aging, exposure to light, temperature changes, and moisture content," says Carrie Spoonemore, co-creator of Park Seed's From Seed to Spoon. Depending on seed type, genetics, and storage conditions, seeds can remain viable for varying lengths of time, from a few years to several decades.

What a Seed Packet's Expiration Date Means

Many seed packets come with an expiration date, which usually indicates the period during which the seeds are guaranteed to germinate. "This date can serve as a guideline for consumers as an optimal timeframe for planting for the best germination and healthy growth," says Spoonemore. "Depending on storage conditions and other factors, the seeds can remain viable beyond the date."

Why Certain Seeds Last Longer Than Others

Some seeds last longer than others depending on several factors. "Seeds with a long lifespan often have hard seed coats that protect against environmental factors and mechanical damage.

Examples of longer-lasting seeds include:

• Beans
• Peas
• Squash
• Broccoli
• Pumpkin
• Tomatoes

"Seeds with a shorter lifespan have higher moisture content and are more susceptible to degradation," says Spoonemore.

Examples of seeds with a shorter lifespan include:

• Lettuce
• Onion
• Parsley
• Carrot
• Corn
• Parsnip

How Long Seeds Last

Seed viability can vary depending on the specific species and storage conditions, but these are the general estimates for how many years seeds remain viable for, Spoonemore says.

• Vegetable seeds: Three to six years
• Fruit seeds: Two to six years
• Flower seeds: One to three years
• Herb seeds: One to three years

How to Know If Seeds Are Still Good

Use Martha's foolproof method to know if your seeds are good or no longer viable. She folds 10 seeds in a moist paper towel and places them in a resealable bag, labeling the bag with the date and type of seed. She then waits to see how many seeds germinate. Multiply the number of seeds that germinated by 10 to calculate the percent of germination. More than 70 percent is passing. If between 40 and 60 percent of the seeds germinate, she says to sow thickly. If less than 40 percent germinate, consider buying fresh seeds.

How to Store Seeds So They Last Longer

To ensure your seeds stay viable, consider these tips from Linda Langelo, horticulture specialist at Colorado State University.

• Storage Conditions: Store seeds in a cool, dry place with a temperature around 45 degrees and less than 8 percent humidity.
• Location: The basement, a dark closet, or the refrigerator are good options.
• Avoid Heat and Humidity: Sunlight, high temperatures, and excessive humidity can degrade seeds quickly.

Remove seeds from the packages they came in and store them in a labeled airtight container. "To be sure your container is airtight, submerge it underwater and if it does not leak, then it is an ideal container," Langelo says. In the bottom of the container, add a desiccant, like rice, to absorb moisture. If you're saving seeds from plants in your garden, make sure the seed you chose is in good condition from a healthy plant.