Not all of the seeds that you purchase always end up in the ground for planting the season that you purchase them, which means the left overs require storage. However, if they aren’t stored correctly, you risk losing that seed to environmental factors that could affect your crop – or maybe it won’t grow at all. This article is about how to correctly store your seeds until next season.
So you’ve just received your latest shipment of 25 seeds from your favourite seed bank—and you only plan to plant 5 or 10 of them this season; or you’ve just finished this season’s harvest and you’d like to store the seeds you’ve collected for your next crop … Proper storage of cannabis seeds is an essential aspect of ensuring the viability of future marijuana crops.
There are two types of seed categories:
- Orthodox Seeds – these seeds enter a dormant stage and will survive drying;
- Recalcitrant or Unorthodox Seeds – seeds that will not survive drying and are susceptible to desiccation injury.
Cannabis seeds are the orthodox type, or desiccation-tolerant, and can be prepared for long-term storage without risking instability.
Key factors to consider when storing seeds are environment and container. Environment is important because moisture levels, temperature, and light exposure all play a role in the stability of your seeds, along with oxygen and ethylene concentrations. The container you choose for storage plays an important role in that the proper environment will be maintained if you use the proper receptacle. Hand-in-hand, these factors help ensure the viability of your seeds for either long- or short-term storage periods.
Environmental factors that affect the viability of cannabis seed are:
- Moisture – reducing moisture exposure ensures seeds won’t prematurely germinate or become mouldy.
- Temperature – fluctuations in temperature can lower a seed’s longevity significantly.
- Light exposure – light is required for germination; over-exposure may cause seeds to come out of their dormant stage and encourage tissues to mutate.
- Ethylene concentration – ethylene is an important natural plant hormone; seeds begin to produce ethylene immediately after exposure to water or moisture (another reason low moisture conditions are necessary during storage).
- Oxygen concentration – lowering oxygen exposure will reduce or prevent seed respiration during storage, thus deterring premature germination.
It is important to dry your seeds gradually and thoroughly before storing them—although not to 0% moisture, as this can result in the death of a seed. During ripening and drying, cannabis seeds will prepare for dormancy by slowing or stopping most physiological processes. Ideal moisture percentage is 2-3% and can be achieved by placing a desiccant in the storage container with your seeds. (A desiccant is a hygroscopic substance that induces or sustains a state of dryness in its vicinity (draws out water). Commonly found pre-packaged desiccants are solids that adsorb water, e.g., silica gel packs. These can be found at Wal-Mart, Uline.com, or your local florist!). Rice is also known to be an effective desiccant, but should be replaced periodically. The use of a desiccant when drying seeds greatly improves their stability.
Keep cool, keep dark, and keep dry! Maintaining a constant environment with little or no fluctuation is vital to ensure the stability your stored seeds.
The jury is still out on the best location for optimum storage results—each having pros and cons; here are the most common recommendations:
- Refrigerator – your refrigerator is cool and dark, yes—but there is also a fluctuating moisture factor to consider each time the door is opened and closed. Storage in a refrigerator with a desiccant in an air-tight container is a viable option for seed stability and may adequately deter mould production. Storage toward the back of the fridge where the least moisture is present is preferable.
- Freezer – despite popular belief, the freezing method itself actually destroys cells within the seed. Therefore this method is not recommended. There is special laboratory equipment that can be used for slowly bringing the seeds down to a temperature where they are not damaged, but most growers do not have this equipment. If you are going to use the freezer, put the seeds in an airtight, vacuum sealed bag or container with a food grade dessicant satchel.
- Room Temperature – for storage lengths of a few years or less, keeping seeds in the proper airtight container at room temperature (such as in a closet or closed cabinet) with a desiccant is also satisfactory.
If the seed bank you order from packed your cannabis seeds in an environmentally controlled container with vacuum seals and moisture controls—such as a Mylar bag containing a desiccant, it may be best to leave their packaging intact for storage. If you are preparing your own seeds for storage, consider investing in a home vacuum sealer.
If you don’t have a vacuum sealer available, be sure the container you choose is airtight—such as a glass jar with lid. Most plastic containers are not recommended, as their seals are not always airtight; additionally, a water molecule is small enough to get through the pores of plastic containers—plastic containers are best for short-term storage only. On that note, plastic baggies, such as Ziplocs, are not recommended, as they allow light and temperature to fluctuate, and they are not sufficiently airtight.
Containers with lids and bodies made from two different materials (such as glass body with a plastic lid, or plastic body with a metal lid) are not favourable, as different materials expand and contract at different rates. This permits moisture to intrude and/or exposes your seeds to temperature fluctuations.
Overall, glass containers are highly recommended for optimum storage conditions. They are suitable for long- and short-term storage. A glass jar with a glass lid and a ‘lightening closure’ is ideal—easily accessible and reusable—these containers are airtight and help maintain the constant environment your seeds require.
Using a desiccant inside your seed storage containers has several advantages. A desiccant will maintain moisture levels of 2-3% inside your airtight container during storage period; desiccants will also absorb excess ethylene produced naturally during the aging process, thus extending the life of your seeds. Silica gel packs are reusable, saving you time and money as well. Again, rice is also an effective desiccant, but should be replaced periodically for optimum results.
- Labelling – if you are storing several different strains of cannabis seeds, internal or external labels are recommended. Labels will also help keep light exposure to a minimum.
- Desiccant – Place a layer of cotton or wool between the desiccant and your seeds to create a physical boundary between them. This helps absorb initial excessive moisture and ensures seeds will not be physically disturbed.
- Seeds – Add pre-dried seeds to your container and seal.
- Place seed container in desired storage location and wait!
Cannabis seeds are natural, living things and should be handled with care. When properly stored, you can expect your cannabis seeds to remain viable for approximately 5 years—perhaps longer. After 5 years, germination rates tend to drop; however, plenty of folks have successfully grown plants from seeds that were ten years old or more. Enjoy the fruits of your next harvest!