Have you ever planted seeds and waited patiently for sprouts to emerge only to discover that they never germinated?  Not only is it frustrating, but it also sets your planting timetable back because you have to start over.  While there are several reasons why a seed might not germinate, most seeds, given the right conditions, will germinate before they expire. But how do you know when seeds will expire?  A seed’s shelf life depends primarily on two factors: plant variety and storage methods. 

Seed Variety

Plant variety goes a long way in determining seed longevity.  Some seeds, like cucumber and basil, will last about five years.  Other seeds, like onion and parsnip, are viable for only about one year.  The chart below provides an alphabetized list of over 50 different varieties of vegetables and the approximate number of years they are expected to be viable.

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Storage Method for Seeds

The other factor that helps determine seed longevity is the storage method you use.  That is because seeds require water, oxygen, certain soil temperatures, and sometimes light, in order to germinate.  Thus, if they are stored in an air-tight container, void of moisture, oxygen, and light, their shelf life can be maximized.  I store seeds that I have saved from my garden in small plastic bags with zip closures, inside seed-packet sized envelopes.  I then organize them in a seed storage box.  This method is very popular among many gardeners.    

Other gardeners advocate storing seeds in jars in the refrigerator, while still others place them in the freezer.  Depending on the number of seeds you store, using jars may take up needed space in your refrigerator and freezer. If you opt for either of these methods, it is recommended that you add a desiccant to the jar to absorb any moisture.  When you are ready to remove the seeds, allow the jar to come to room temperature before opening it to prevent condensation from forming on the inside of the jar and possibly damaging the seeds.

Conduct a Seed Viability Test

Before you plant seeds that have been in storage, it is a good idea to test them to determine the germination rate, which is the rate at which a group of seeds will germinate given the proper growing conditions.  (You can learn how to conduct a simple seed viability test here.) For example, a germination rate of 75% means that 75 out of 100 seeds will likely germinate if sown in a favorable environment.  So while a broccoli seed may have a shelf-life of three years (see chart below), if it has not been stored properly, it will not achieve the 75% germination rate determined by the Federal Seed Act to be the minimum acceptable rate for seeds sold in interstate commerce. (You can learn more about the minimum expected germination rate for almost 50 different kinds of vegetables here.)

Like most things in life, seeds don’t last forever.  But by learning the shelf life of your seed stock, you can determine how long you have to use the seeds before they expire.  Combining this knowledge with the proper storage methods will enable you to maximize the viability of your seeds, thus, bringing you one step closer to a bountiful harvest. 

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