How to Preserve Seeds to Plant Next Year

The end of the warmer months can be depressing for the avid gardener. Thankfully, seeds from past blooms give hope for future plantings. But seeds don’t last forever, and the older they get, the less viable they are. How you store your seeds can extend or decrease the seed’s lifespan. Here’s how to preserve your seeds so you can plant them next season, and for years to come.

How long do seeds last?

Seeds seem like lifeless pods waiting for the right environment to split open and grow into something actually alive. Actually, seeds are already alive, but inactive. As Garden Professors explains, seeds are still involved in life-sustaining actions like respiration, just not on the scale of a growing plant. When a seed is planted and reaches germination, things like respiration speed up. “A large amount of stored energy is needed to get through germination and sustain the seedling until it has its first set of true leaves and can photosynthesize on its own,” Garden Professors notes. If the seed does not have the viability necessary to produce this level of energy, it will not germinate. A seed needs to be healthy to get through the strenuous process.

Seed viability depends both on the type of seed and how it is stored. As the Micro Gardener explains, “the onion family and parsnips typically only last a year, so need to be used quickly. Whereas basil, radish, and cucumber seeds can last an average of five years.”

Though herbs and vegetables have differing shelf lives, generally seeds stored in a cool, dry place should last about three to five years before viability begins to decrease. According to the Micro Gardener, seeds exposed to heat and humidity will suffer a decrease in viability, while seeds kept in the fridge can last up to a decade.

Some seed manufacturers use this information to determine the expiration dates printed on their packaging, but if that date has passed, that doesn’t mean your seeds have gone bad. Expired seed packets still have a chance of germinating, but you’ll want to plant them as soon as possible.

How to make seeds last longer

To extend your seeds’ lifespan, first make sure they are kept dry, as heat and humidity will decrease the likelihood they will germinate later. If your seeds are damp, you can dry them on a paper towel or newspaper before putting them into storage. Make sure the surface is not in direct sunlight, which can also damage viability.

Next, grab an airtight container. Good Housekeeping suggests storing seeds in tightly sealed mason jars or glass containers with gasketed lids, though a Ziploc freezer bag will also suffice. To ensure the seeds stay dry, they also advise pouring two tablespoons of powdered milk into several layers of tissue or paper towels, folding it into a little pouch or packet, and adding it to the jar or bag alongside the seeds. (If you have some lying around, this is also a great excuse to bust out old silica gel packets.)

After the seeds are sealed up tight and protected from moisture, put them in a cool, dry place until you are ready to plant them. The best place to store seeds is in the refrigerator. Epic Gardening states the optimal storage temperature is “40 degrees Fahrenheit (4 degrees C) or lower, but [it] should not drop into sub-freezing temperatures, as that kills some forms of plant embryo.”

When you’re ready to sow the seeds, take them out of storage location and let them warm to room temperature before germinating or planting them. As with any packet of seeds, you’re still going to have some duds, no matter how carefully you stored them, so, don’t be alarmed if some of your seeds didn’t make the journey through time intact. As long as you’ve kept things cool and dry, you should have enough strong, viable seeds to make a garden.