Marijuana seeds should be kept in a cool, dark place such as a basement or in your refrigerator. They should be in an air-tight container and must stay dry. Putting a cotton ball in with the seeds before storage can help suck up any extra moisture (this is why you often see little bits of cotton in seed breeder packs).
Heat and moisture ‘signal’ to cannabis seeds that it’s time to sprout, so as long as you keep the seeds in a dry, dark environment they can remain viable for years. I have heard cases of seeds sprouting after being in storage for 5 or even 10 years. However, you will notice that older seeds take longer to germinate than fresh seeds and a few of them may not sprout at all. As time goes on, fewer and fewer of the seeds will successfully germinate.
However, if you’re planning on crossing your own plants and making your own seeds, you’ll need to know how to harvest, dry and store them if you’re planning on keeping them for a while before germinating them; knowing how to store cannabis seeds properly is quite an important tidbit of information if you’re a professional cannabis grower.
One of the first things to keep in mind is that whatever container that you store your seeds in needs to block out all light. If you’ve ever germinated cannabis seeds before, then you know that light is an important factor when it comes to the probability of the seed germinating or not. If your seeds are exposed to light for too long, they may end up too weak to germinate; even if they germinate they might have quite a hard time starting off.
Drying Cannabis Seeds
This obviously depends on your climate too, as there are places that have incredibly high humidity and others that are quite dry, which can directly impact how you have to store your seeds. As a general rule of thumb, we recommend keeping them in a low-humidity container, and if you live somewhere incredibly humid you might have to use specific methods to decrease humidity.
However, for long-term storage you’ll need to store them at around 6-8° – if you plan on storing a large amount of seeds, we recommend buying a small cooler for that specific purpose to keep them at a low, constant temperature; opening your fridge can cause temperature changes, so keeping them with the rest of your products is probably not the best idea.
Humidity is another incredibly important factor that can determine the success rate of your seeds. Relative humidity is essentially what causes seeds to germinate, so they’re quite delicate at this stage and you don’t want them accidentally germinating; keep relative humidity low in their container.