Are Seeds Viable After Long Term Storage?

1695030People buy seeds in bulk to save for the future. The most popular and truly important questions on these people’s minds is viability. They want to know if it is worth buying a large amount of seeds today. Will the seeds be viable after a collapse? Will it be viable when they retire and get the time to be full time gardeners?

These are all valid questions. Unfortunately, the answer is a bit lengthy and requires some explaining.

Seeds you buy at the local store are stamped with a date. It indicates when they need to be used by. Does that mean if you try planting the seeds they will not sprout after indicated date? That’s a tricky question as well.
Many of the seed packs you buy in the store are hybrids. They are not meant to be long term solutions to a garden.

There is a very good chance you will have low sprouting numbers. Hybrid or GMO seeds are not suitable for long term storage. The date on the package is a pretty good indication of how long they will be viable for.

Heirloom seeds are different. Heirlooms are harvested, dried, packaged and sold with the intention of seed storage. Heirlooms are also meant to be stored to use for future growing seasons. That is the very nature of heirloom seeds. People grow the seeds because they want to continue a tradition. They want to maintain the history of certain plants that have been passed down through generations.

1622482Before you buy seeds to store for a long period of time, you need to make sure you are buying from a reputable seller. The way the seeds are harvested and dried is critical to its viability. If the seeds have a higher moisture content than about 10 to 12 percent, there is a chance they will mold, even in a sealed container.

Seeds that have been dried too much may crack and will not be viable. You are not expected to have a device to measure the water content of the seeds. In this article we will cover how to judge the viability of a seed based on other tests.

Consider the process of drying and storing before you buy seeds from just anybody. Not all heirloom seeds are the same quality. Seeds that have low germination rates before storing are more likely to not germinate at all. If your goal is long term, you need to choose wisely.

Storage Methods

1Seed viability has a lot do do with the way the seed is stored. Temperature fluctuations will have the most harmful impact on stored seeds. The goal is to find a place to store the seeds where the temperature is fairly even and doesn’t vary by more than a few degrees during the storage period. Once you put your seeds in your chosen storage spot, it is best to leave them there. Taking the container out of the area results in a temperature change. Opening the container introduces air, which results in moisture. You must be prepared to put the seeds in their spot and leave them be. Pulling them out once a year to collect seeds for planting is okay. However, you must go through the process of properly sealing and replacing the seeds as quickly as possible.

There are a couple of options you have after you receive your seeds in the mail. How you store the seeds is extremely important. It has a serious impact on how long the seeds will be viable for. Storing seeds in less-than-ideal conditions will absolutely shorten the shelf life or viability of the seeds. If you talk to other gardeners who store seeds, they will likely each have different answers about the best way to store seeds. These are the facts. You can make your own decision based on information that has been gathered over the years and passed along by experts in the field.

1277634There are a few “enemies” that will hurt the viability of your seeds. These are things you want to control or limit in order to give your seeds the best chance of being viable after several years.

  • Light
  • Moisture
  • Heat
  • Insects
  • Temperature fluctuation
  • Seeds that are not dry enough before storage
  • High humidity
  • Higher oil content in seeds tends to result in reduced shelf life i.e. lettuce, spinach and parsnips
  • Seeds stored over 60 degrees Fahrenheit will lose viability. It is estimated for every 5 degrees below 60, the storage time doubles. For every 5 percent decrease in humidity, the shelf life increases.


1349218Freezing is the best choice for storing your heirloom seeds. Freezer storage gives you the best germination rates after long term storage. Seeds that are stored in the freezer are dormant. The temperature is regulated and you don’t have to worry about moisture building up inside the container. Store the seeds in the back of the freezer. This will ensure the seeds don’t warm up when the door is opened for prolonged periods of time. Keep the seed packs away from the fan as well to avoid moisture and temperature fluctuations.

The seeds can be stored in sealed bags. A Food Saver bag or something similar is the best option and removes the oxygen from the bag before it goes into storage. Keeping the seeds in the freezer eliminates the risk of insect infestation ruining your supply. If you are going to use a bag, choose the Ziploc bags designed for the freezer. They are more durable and keep out more air than the standard sandwich bag.

Seeds that are not dry enough and have a high moisture content will swell when they freeze. The water in the seed swells to the point it damages the inner part of the seed, destroying its viability. This is why it is critical you only buy seeds from a dealer who has a proven track record.


The refrigerator is an option. It provides a regular cool temperature that will inhibit any kind of insect activity and keeps the seeds from germinating. You can store the seeds in a sealed bag or a sealed jar. Adding a silica packet is a good idea and will absorb any leftover oxygen in the container.

1812423The issue with refrigerators is temperature fluctuation. Each time a refrigerator is opened for more than 30 seconds or so, the temperature inside is going to warm up. If this happens repeatedly, you will be dealing with serious temperature fluctuations that could damage the seeds.

Another issue with refrigerator storage is the light. Every time the door opens, the light comes on. Light is heat. It only takes a little heat to create condensation in the container. You can protect your seeds by wrapping the jar with burlap or fabric to keep it dark. Placing a bag of seeds inside a paper bag is also an option. Store the seeds in the produce drawers. You can label the drawer indicating there are only seeds in it, which will hopefully keep people from opening the drawer and exposing the seeds to the warm air in the room.

Dry Storage

There are many different ways to store seeds on a shelf in your pantry, basement or garage. The key is to keep out as much air as possible. Air that is trapped inside the bag or jar you store the seeds in produces moisture. Adding a silica packet to each package will help absorb any air in the container and keep the seeds safe from moisture.
The real issue with storing seeds on a shelf somewhere is temperature control. The storage area must be cool and dry; preferably below 50 degrees. A garage or garden shed in the summer is going to be hot and can actually result in seed germination. During the spring and fall months, the moisture level could be an issue. Even room temperature storage will shorten the shelf life of your seeds.

In general, dry storage is the least favorable place to store your heirloom seeds for long-term viability. The temperature fluctuations can cause condensation inside the container which will result in the seeds being destroyed by mold or germinating too soon.

You may also have an insect infestation. Weevils are extremely tiny. The eggs may be in or on the seeds you store. If the seeds are in dry storage, the weevils will hatch and will destroy your seeds. It isn’t just weevils you have to worry about. There are plenty of other critters who will appreciate a seed snack.

You can help repel the bugs and make your seeds less inviting by adding bay leaves to the jar or bucket you are storing the seeds in. This isn’t a full-proof solution, but it does help. Mice and other pests will eat your seeds if they are not properly stored. Glass jars are ideal. Placing the seeds inside sealed Mylar bags and then placed inside a sealed plastic bucket is another way to keep the bugs and mice out.

Jar Storage

1560105According to Suzanne Ashworth, in her book Seed to Seed, jars with solid lids can become premium seed banks and seed vault containers. It can be a spaghetti sauce bar, a canning jar, or pickle jar. Anything that you can get cleaned, dried out, and has a good solid lid (that isn’t damaged) can be used as seed banks and seed vault containers.

Before using jars as heirloom seed containers, make sure to dry them out first. If you put the heirloom seeds in cold storage, be cautious. Always lay the lid off for 4-5 hours before putting them back in. Allow the seeds and lid to return to room temperature. You don’t want moisture and heirloom seeds inside the same jar. Once it gets back to room temperature, put it back in cold storage. .

Jars are the best seed vaults money can buy. What’s great about this fact is that it’s basically free. You may already have a jar in your home with a good lid.

Additional Tips for Storing Seeds

Whether you put your seeds in the freezer, refrigerator or in a closet, you will make your life easier by instituting some of these helpful tips. The viability of seeds has a number of different factors and influences. Every little extra thing you do that improves the longevity of your seed storage is worth it. These are tips that have been passed down and the result of some trial and error. It’s always much nicer to learn from other people’s mistakes and mishaps!

  • If you have ordered seeds in bulk, remove them from the package and divide them up into smaller packages. This prevents you from opening the package several times and allowing light and oxygen into the bag. It is unlikely you would plant 200 seeds of the same variety all at once.

    Post memo.

    Post memo.

  • Label each package. Seeds can be hard to identify to the untrained eye. The less time you spend rummaging around in the freezer or refrigerator, the less warm air you are letting in.
  • Store seeds in small Mylar bags. The bags can be sealed to keep out air and the light. The bags are easy to write on or label.
  • Write the date you stored the seeds, how many seeds are in the container and the type of seed on every bag, jar or box of seeds you store.
  • Always use the oldest seeds first. This is a bit of a given, but you want to make sure you are using proper rotation in order to keep your seed bank as viable as possible.
  • Note where you bought the seeds and when. In the following years when you test the seeds for germination, you want to know where you got them from and whether the germination rate is good or bad. This will tell you where to buy from in the future.
  • Only remove the seeds you will be planting. Do not remove seeds from the freezer, allow them to warm and then put them back in the freezer.
  • Before planting seeds that have been stored in the freezer or refrigerator, allow them to come up to room temperature overnight first. Placing them on the counter is ideal. Do not put them in a window to heat quickly.
  • If you do not have silica gel packs, putting a couple tablespoons of powdered milk in the container will help absorb the moisture. Rice can also be used as an absorbent material.

Testing Viability Before Planting

If you are not sure about a seed pack’s viability, you can do a simple germination test. You’ll have an answer within a few days. It is always a good idea to do a germination test on a handful of the seeds you have just purchased. If the germination rate is low, you can deal with the dealer right away. It will also prevent you from wasting time by storing seeds that are not viable from the get go.

1-Remove 5 to 10 seeds from your package. Reseal the seed container and replace it in your chosen storage.
2-Dampen a paper towel or a coffee filter.
3-Place the seeds on one half of the paper or filter. Fold the paper over the top of the seeds so they are touching the damp towel on both sides.
4-Place the damp towel into a sandwich bag and seal it. This will help keep the towel moist. You don’t want it to dry out at all. Place the bag in a warm area, but not in a window with direct sun. Seeds need to be around 75 degrees to sprout. Cool crops, like peas and spinach, prefer cooler temperatures for sprouting.
5-Wait three days before checking on the status of your seeds. If the seeds have sprouted, you have good viability. If you don’t see any sprouts, dampen the towel and replace it in the bag for a couple more days. The towel should be damp—not wet.

You will have an idea of your seed viability based on this germination test. If only 2 out of 10 seeds sprouted, you know you have low viability and the chances of the remaining seeds in the package growing into healthy, food-producing plants is low. You can repeat the germination test if you want to be absolutely sure.

Visual Inspection

1634307In some cases, you can determine the viability of a seed by simply looking at it. This requires experience and training, though. But once you have it, you can save time and energy. Some experts only needs a moment to know right away whether a seed is going to sprout.

  • Seeds that look plump are generally in good shape
  • Seeds that are pocked or look overly dry are generally not viable
  • Seeds that are slightly green (except for peas) or have a pale color were likely immature at the time of processing and are not viable

You can give your seeds a float test to determine whether they are hollow inside. A hollow seed is not viable. If the seeds float, they are likely hollow inside, which could be the result of an insect problem. Seeds that sink or hover near the bottom are generally viable.

Another test is to cut a seed open and determine if it is hollowed out or shriveled inside. Hollowing or shriveling is a bad sign and means the seed will not germinate. If it is full inside, the seed is viable and the batch is likely in a similar condition.

Seeds that are long, like a bean, should snap when you bend it. This indicates the seed has been dried appropriately. Smash a corn seed. If is shatters and turns to dust, the pack is appropriately dry and will store well. You can use the smash method with peas and beans as well.

When in Doubt

1810062Do your due diligence. Test germination and ask help for visual inspections. Once you’ve determined the seeds have a low chance of sprouting, continue to plant the questionable seeds.

A seed’s viability also depends on how long the seeds have been in storage and how they were stored. If you haven’t done a germination test and still question their viability, plant extra seeds.

You will want to double your normal planting to ensure you get the number of plants you are hoping for. Plant questionable seeds somewhat closer together than you would normally. If they sprout, you can gently replant them in their own section in the garden. Putting seeds in the ground doesn’t take any extra energy. You can hope for the best, but expect limited germination.


There are plenty of ideas and guesses about seed viability. Different companies and different gardening experts all have their own ideas about how long seeds will store for and still be viable. The following chart is a guideline. It is by no means a definitive, set in stone chart. It will give you an idea of what to expect and help you to plan accordingly. Always do a germination test to get an idea of what you are working with.

The chart below is assuming you are storing your seeds in optimal conditions.

Type of Seed  Estimate of Seed Shelf Life 
Asparagus 3 years
Beans—any variety 3 to 5 years
Beets 3 to 4 years
Broccoli 3 to 5 years
Brussels Sprouts 4 years
Cabbage 3 to 5 years
Carrots 2 to 3 years
Cauliflower 4 years
Celery 2 to 3 years
Corn 1 to 2 years
Cucumbers 5 to 10 years
Eggplant 3 to 5 years
Kale 4 years
Lettuce 2 to 5 years (variety influences longevity)
Onion 1 to 2 years
Parsnips 1 to 2 years
Pea 3 years
Pepper 2 to 5 years
Radishes  5 years
Spinach 1 to 3 years
Squash 4 years
Tomato 4 to 7 years
Watermelon 4 to 5 years

This chart is a general idea. You may discover your seeds are viable a year or two longer than the average. It really comes down to the way the seeds were processed and how they were stored. There is no one answer.

With this information, you can make the best decisions for you and your seed storage. If you suspect you have some seeds that are getting close to losing their viability, get them in the ground so you can harvest new seeds from the plants. Storing seeds is something many people do to give them a little security for the future. Choose seeds based on what your family eats and have fun with it. Make it a family project to prepare seeds for storage.

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