Seed Storage 101

Seed Storage 101

Storing seeds in the proper conditions can extend a seed's life for up to 5 years. Whether you're storing extra seeds or growing a library, here are some storage tips to get the most out of seed packets.

What should I store my seeds in?

Consider the fundamental factors of seed germination; light, temperature, and moisture. When storing seeds, we want to provide the opposing conditions: a dark, cool, and dry environment. There are many options for seed-storing vessels: glass jars, food storage containers, used medicine bottles, plastic storage boxes with lids, or resealable cans are all viable possibilities. According to a study by Jeffery McCormack, seeds stored in glass and cans proved to have the highest germination rates over the longest period; some studies have resulted in almost 90% germination even after 5 years.

seed storage rating chart

What about sealable polyethylene or polyester bags? An important thing to keep in mind is that not all plastic bags are the same. Polyethylene bags must have a thickness of 0.075 to 0.1 millimeters. Common household freezer bags will work well, while most sandwich bags are too thin and porous. Polyethylene and polyester bags can be found at most supermarkets and can preserve viability for at least 2 years, 5 years max in proper conditions.

Seed Coats

The seed coat is the seed's primary defense mechanism against oxygen and moisture in order to maintain a low metabolism. The seed coat also protects the embryo from potential danger from external environmental factors. The hard seed coats of peas, beans, okra, hollyhock, and sunflowers contribute to their ability to preserve viability for long periods of time. Seeds with a thinner or softer seed coat, like edamame, lettuce, onions, parsnips, and leeks, are likely to have a relatively shorter life, and should be used annually for best results.

Long-Term Storage

As a general rule of thumb, longevity increases as temperature decreases, but that doesn't mean that you need to refrigerate or freeze your seeds. Make a plan. If you are going to be using your seeds next season or even the one after, a cool, dry, dark spot will preserve viability well. If you aim to store your seeds for 2+ years, storage temperatures should be 40���F or lower; 35-40���F is ideal. If longer storage times are desired, we recommend a small refrigerator dedicated to seed storage so you can set it to a preferred temperature.

Remember "CDD":

cool dry dark

  • Cool: Cool temperatures lower metabolic rates in seeds. A cool spot in your basement, closet, or utility cabinet would be suitable place to store your seeds.
  • Dry: Make sure that your seeds are dry and in a low-humidity environment. The more humidity, the more moisture, which can lead to premature germination or rotting.
  • Dark: Make sure to keep seed-filled translucent containers in the dark; exposure to light may cause a greenhouse effect and raise temperatures inside.

At-Home Viability Test
If you're curious about how viable your seeds are, you can conduct your own germination test with just a zip lock bag, misting bottle, and a paper towel; simply follow these steps:
  1. Run a paper towel under room temperature water and wring out the extra water. The seeds will rot if the towel is too wet.
  2. Place 10 seeds in a line and neatly fold the paper towel. Place inside of a plastic bag and seal. This will help retain moisture and increase humidity during germination.
  3. Keep in a warm place (about 70��� F) for a few days. A warm windowsill or the top of the refrigerator would work well.
  4. Make note of the "Days to Emerge" on your seed packet, since this will be the amount of time that you can expect your seeds to germinate by.
  5. Check on your seeds in a few days to see if your seeds have germinated and to ensure the paper towel has not dried out. Spray the paper towel with a misting bottle to moisten it as needed.
This viability test will give you a germination rate, that will tell you what percentage of your seeds will germinate. If 8 out of 10 seeds germinate, the germination rate is 80%. If less than 70%, it may be time to get new seeds.

Sources: McCormack, Jeffery H. "Seed Processing and Storage: Principles and Practices" Saving our Seeds. Published 2010.
Written by Madeleine Pesso

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