There are many disagreements on how to store marijuana seeds: cold environments like freezers or cool, dark and dry locations. Our perspective is something a bit in between. We think that a fridge works best to keep the seeds viable longer, but that does not mean that this is the only option that works. A seed is just a small portion of the marijuana life cycle, so when placed into a cool or even cold environment, this slows down the life cycle that the marijuana seed is going through. However, this also has the benefit of slowing down the degrading process that a seed would normally go through. This benefit means that your marijuana seeds are going to last you longer than normal because of this near-pause of the marijuana seed's life cycle. It has to do with the same mindset that tells us to put fresh produce and herbs in our fridge: it prolongs their life!
The easiest thing to do is find some type of a small, airtight container. Film canisters that keep all light out are ideal for this purpose. Then put a few grains of uncooked rice or a few crystals of silica on the bottom of the container to soak up any moisture that may seep in. You can either use a bag or an envelope for your seeds, but we prefer the envelope method due to the fact that any trapped moisture can escape from around the seeds. You can buy seed envelopes at specialty nurseries or organizations that work with seed-savers. Make sure to label your seeds on the outside of the bag or envelope so it does not get confused with any other seeds in your collection. You will want to include the variety, quantity of seeds in the container and the date to make planting next year easier. Once the bag or envelope is in the container, place them in your fridge. This will control all of the enemies of your seeds: light, moisture and excess humidity. A list of your seeds that stays out of the fridge will also minimize the exposure that your seeds would face if taken out of the fridge to itemize your seeds.
When you want your seeds to last through storage, then you need to track temperature and humidity around your seeds. The relative humidity can be most devastating out of these factors, so watch it closely. There is a bit of a conundrum when it comes to marijuana seeds as they can both absorb humidity from moist environments and dry out in arid environments. The more you can decrease the humidity, the more your marijuana seeds can last. A good rule of thumb is every 1% of decreased moisture equals a doubling of storage time that marijuana seeds can survive. The higher the moisture content of the marijuana seeds, the harder germination is to hold on to. If your marijuana seeds have moisture above:
- 40% to 60% germination will typically occur
- 18% to 20% heating may occur
- 12% to 14% fungi growth begins on and in the seeds
- 8% to 9% insects become active and begin to reproduce
Keeping the environment dry will help prevent all of these issues, including heating. This is when the marijuana seeds respire and become no longer viable. Increases in temperature and moisture will quickly kill off your marijuana seeds just like an invasion of micro-organisms or insects would. The general rule of thumb for temperature is for every 41°F | 5°C decrease, you will also double the storage life of your marijuana seeds. A constant refrigerated temperature around 41°F | 5°C is ideal, but this is typically a bit warmer than most fridges. If you go too cold then vitality can cease, leaving no viability to your seeds when you go to plant them. Rumor has it that seeds have lasted and been viable up to five years after starting storage if stored properly, so keep that in mind when you think about storage for your marijuana seeds. This may not be able to be accomplished by everyone, but it is a good goal to strive for.
Some websites recommend that you store your marijuana seeds in a freezer, but we do not believe this is a good idea. Freezing typically causes damage to marijuana seeds on a cellular level which will leave them unable to sprout or germinate when you go to plant them.