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Q: Do seeds expire? I have many flower and vegetable seed packets dating back several years and don’t know if I should keep them or throw them away and buy new seeds.
A: Under ideal storing conditions, your seeds would likely be viable. But nothing is perfect, especially when it comes to providing the requirements to keep seeds happy and capable of germinating from year to year. For that, you need the right combination of humidity, darkness, and cool temperatures. As the temperatures in our homes fluctuate with the seasons, maintaining a “Goldilocks” environment is a challenge, but it’s not impossible. Even when stored under the best conditions, seeds expire. Here’s what you need to know to get the most out of that little seed packet.
Humidity and temperature are critical factors in why seeds go bad.
Seeds have one thing in common: They all deteriorate over time, but some do it more quickly than others. Seeds stored in a warm, humid environment will decline faster than those stored in the darkness where humidity is low, about 10 percent, and the air temperature is between 32 and 41 degrees Fahrenheit.
A lot depends on the seeds’ condition when you place them in storage, and the ultimate kiss of death is moisture. A seed that’s damp when stored will inevitably develop mold and die. A common rule of thumb for an optimal seed storing environment takes the sum of the air temperature in Fahrenheit and the percentage of relative humidity. The total should be less than 100. For most, the refrigerator is the best option. It’s dark, cold, and when stored in an air-tight container like a glass jar, seeds can survive to see another season.
As seeds age, though, their vigor decreases no matter how well you store them. For example, a melon seed that typically has a long shelf life of five to six years may germinate well in its fourth year but produce weak growth and little fruit. In which case, it’s time to pitch the packet and buy new seed.
So, how long do seeds last? It depends on the type.
There is no one-size-fits-all when it comes to estimating seed longevity. And the truth is, no matter how diligent you’ve been about seeing to their every need, seeds eventually peter out. Every seed packet includes a “packaged on date,” which is a good gauge for determining their lifespan. For example, most annual flowers like zinnias or cosmos have a one-year lifespan. The same is true for vegetable seeds like onions and parsnips.
Here’s a list of some of the most common vegetable and herb seeds with their corresponding life expectancy estimates when properly stored.
Beans, 2 to 4 yearsCarrots, 3 to 4 yearsSweet Corn, 1 to 3 yearsCucumber, 3 to 6 yearsLettuce, 1 to 6 yearsMelon, 3 to 6 yearsPeas, 2 to 4 yearsPeppers, 2 to 5 yearsPumpkins, 4 to 6 yearsTomato, 3 to 7 years
Basil, 3 to 5 yearsChives, 1 to 3 yearsCilantro and Dill, 1 to 4 yearsOregano, 4 yearsParsley, Rosemary, and Thyme, 1 to 4 yearsSage, 1 to 3 years
Follow seed storage guidelines to best preserve them.
Not everyone has a refrigerator to store seed, and a shoebox placed randomly on a shelf in the kitchen isn’t the best way to go. So how do you prevent seeds from expiring? Basements and garages are great places. They’re dark and often much colder than the rest of the house during the winter months. If a basement isn’t an option, a closet that shares a wall with the garage, or any other exterior wall, is usually cooler than a closet located on the house’s interior. The most important thing is that the seeds be kept in an area where the temperature remains cool, constant, and dry. The kitchen is hardly the best place.
It’s best to store seeds in air-tight containers, like baby food and mason jars, or anything with a rubber gasket that locks out moisture. For more extensive seed collections stored in envelopes or their original packaging, ammo cans are a great option as they’re air-tight and waterproof. These can be found at most outdoor activity stores that sell hunting, camping, and fishing supplies.
Whether you’ve collected seed from a plant you want to grow again next year or used just a few seeds from a packet and saved the rest, only store dry seed. Moisture is its worst enemy. Just remember, no matter how well you store them, seeds have a mind of their own, and only they know when it’s time to call it quits!