- Cannabis seeds stored in poor conditions will spoil quickly or even germinate (sprout).
- Environmental factors like light, humidity, and temperature will affect the longevity of cannabis seeds.
- If stored in favorable conditions, cannabis seeds will last anywhere between a few months to as long as a couple of years.
- Refrigerated cannabis seeds can last up to a decade.
If stored properly, cannabis seeds can last for a very long time—even up to a decade in some cases. However, if not stored properly, cannabis seeds will spoil.
So that your next grow isn’t ruined by spoiled seeds, let’s break down steps you can take to store your weed seeds in a way that keeps them viable for longer.
How long do cannabis seeds last
How long do marijuana seeds last? The answer is… it depends. Factors that affect this include:
- Certain strains of cannabis will last longer than others. Some strains, for instance, produce thicker seed coatings or harder seed shells that will protect seeds from pathogens and moisture.
- When seeds are harvested will affect longevity. For example, if they were aged or unripe when harvested, they will not last as long as if they were mature when harvested.
- How the seeds have been stored will also affect how long a seed will remain viable. For instance, environmental factors like light, humidity, and temperature can all affect the longevity of cannabis seeds.
How to determine the health of a weed seed
How can a grower tell if weed seeds have gone bad? Right off the bat, there are a few things to look out for:
- The seed feels mushy or brittle
- The seed has visible mold or mildew
- The seed smells rancid or sour
If any of these things are present, it’s likely that the seed has gone bad and will not be viable for planting.
The color of the seed can give you some clues as to its health. A good weed seed should be brown, dark brown, gray, or black. If the seed is green, it’s likely that it’s not fully mature and, as a result, won’t be viable for planting. However, if the seed is completely white (not just on the ends, but white through the middle of the outer coating), there’s a chance that it’s dead and won’t germinate.
The size of a seed can also give you some clues as to its health. A good cannabis seed should be relatively uniform in size and shape. If the seed is smaller than average or has an irregular shape, it’s likely that it won’t be viable for planting.
If the coating on a seed is thinner than usual, brittle, or flaking off, it’s likely that the seed is old and no longer viable. A healthy seed, on the other hand, will have a waxy sheen to its coating. A sign that it is healthy and still viable for germination.
A healthy weed seed should be plump and firm to the touch. A seed that is shriveled or feels hollow is either old or wasn’t formed properly before harvest.
If a seed has any cracks, holes, or other damage to its shell, it’s likely that the seed is no longer viable for planting. If this is the case, it’s likely either a pathogen or moisture has found its way into the seed and has begun to deteriorate it from the inside out.
Environmental factors that affect cannabis seed viability
There are three key environmental factors that affect the longevity of marijuana seeds.
Let’s explore these now.
Cannabis seeds shouldn’t be stored in direct sunlight. While some people believe that this will help keep them from going bad, the opposite is actually true. Sunlight will cause cannabis seeds to dry out, which will make them less viable and more likely to spoil.
Instead, cannabis seeds should be stored in a dark, cool place. A cupboard or drawer is ideal.
Cannabis seeds shouldn’t be stored in an environment that is too humid. If the humidity level is too high the air is too moist, this will signal to the seeds that it’s time for germination. Or, worse, high humidity could put the seeds at risk of exposure to rotting, molds, or other pathogens.
For this reason, it’s a good idea to store cannabis seeds in an environment that is relatively dry. A good rule of thumb is to store your seeds at a relative humidity between 20% and 30%.
Cannabis seeds should be stored in a cool, dark place at stable temperatures. Sharp temperature changes can affect seed viability. If storing for a short period of time (like a week to a month), it’s best to store your seeds at temperatures between 41°F and 77°F (20°C and 25°C).
If however, you’d like to store cannabis seeds for longer, they can be stored in a fridge.
The best way to store cannabis seeds
For long-term storage, keeping marijuana seeds in a fridge is the best method. When stored in a fridge, cannabis seeds can last for years—even up to a decade in some cases.
To store cannabis seeds in a fridge, simply place them in an airtight container, light-proof container. A dark-colored vacuum-sealed bag is ideal to further protect them from moisture and light. Or you could use a readily available container like an empty plastic vitamin jar.
Temperatures of between 41-46°F, or 5-8°C, are your best bet. Any colder and you risk damaging or cracking the seed’s shell, exposing the embryo to temperatures that will render it unviable.
The float test
Once you are ready to plant stored seeds, an effective method of checking viability is to carry out the float test.
To do this, you need a glass of room-temperature water. Drop the seed into the water. If the seed is viable, after about 15 minutes, it will sink to the bottom of the glass. If the seed is not viable, it will remain floating on the surface of the water.
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