Knowing how to properly store your cannabis seeds isn’t rocket science, but to a beginner grower especially, there’s a lot to be aware of. The key factors in maintaining seeds are storage methods, light, temperature, and humidity. If this looks like a minefield, don’t panic!
In this article, we’ll walk you through the main dos and don’ts of storage – not just the hows, but also the whys – and those precious seeds will be good to grow when you’re ready.
Table of contents
Understanding the Key Elements of Seed Storage
To store marijuana seeds, it’s essential to starve them of the conditions they need to develop. Failure to do this can lead to a drop in germination rate, and you could easily find yourself opening a container of useless seeds which are no longer viable.
Consider all the variables involved in plant growth, and if needs be, carry out further research to better understand how these can impact seed storage. Since most plants see winter as the time of dormancy and spring as the time of new growth, the way you store your seeds should try to emulate the critical conditions of winter, which should keep the seeds from germinating.
The Idea Conditions to Store Cannabis Seeds
Storing seeds at the correct temperature is vital.
This is because warmer temperature changes tell the seed that winter is over, and along with other cues, begins germination. The temperature you store your seeds at must be kept stable throughout the storage period, so avoid storing in conditions where temperature can fluctuate. A cool place is best.
If you’re storing your seeds long-term in a fridge, be aware that the temperature will undergo a slight change every time you open the door. Store seeds towards the back of the fridge, and if possible, try to use a separate fridge purely for seed storage.
Put them in a suitable, light-proof container, and leave them there until you plan on using them. There are different opinions on the correct temperature but aim for somewhere in the region of 5-8°C, or 41-46°F, as this keeps the seeds cold enough to avoid cracking open. But it’s not cold enough to damage the seeds.
Keep humidity levels in check to protect the seeds’ outer shell. If the humidity level begins to rise, the seed can interpret the moisture as a signal to burst into life and start growing. This doesn’t mean you want the storage environment to be as dry as possible. This further damages by dehydrating the seeds. A relative humidity level of 20-30% is best; any higher could effectively spark germination.
Be aware that refrigerator storage does carry some risk of variable humidity and that long-term storage calls for a lower level of humidity around the 10% range. A dry place is the best place.
Outdoors, sunlight is a vital stimulant, and cultivators use artificial lighting inside to help plants grow. Meaning, light is another stimulus to be avoided when safely storing your seeds. Storing seeds in darkness at low temperatures with low humidity is vital for keeping them dormant.
Even the light bulb in your fridge could potentially pose a problem, which is why we recommend stashing them away and leaving them there. If you have a designated fridge for seeds, close that fridge door quickly, and keep it closed until you intend to take the seeds out to plant them. Avoiding too much light exposure is key.
What Should you Store your Seeds in?
The good news is that there are options, most of which are easy to get no matter where you live. There are some caveats to each of these options, which will be explained.
Suppose you’re storing a smaller quantity of seeds over a shorter period (weeks or a couple of months). In that case, an envelope makes an ideal storage solution, as the paper is suitably thick to protect the seeds from light and moisture, keeping them dormant over the short term. The beauty of an envelope is that you can grab a pen and write any relevant details on the pouch to remind you what you’ve stashed away and when. You may want to note the number of seeds, strain details, and date of storage on the outside. When you come to fetch them, you can see exactly what you’ve got in each envelope. If the original packaging meets this criteria, even better.
Toss a desiccant pack in the envelope with the seeds to keep the humidity level stable, or if you’re in a pinch – or if you’re just thrifty – a small handful of rice will do the same job. As long as you don’t use the kind of envelopes with an address window, you can confidently store seeds in an envelope or similar type of pouch in the back of a drawer or cupboard for a shorter time.
These hold a clear advantage over envelopes in that they’re entirely airtight. We’d recommend using the kind that seal with rubber stoppers rather like a mason jar, than plastic lids, simply because most plastic lids can let in small amounts of moisture over time. Again, a desiccant pack is your friend here to absorb any additional moisture within the jar. Use a paper towel or some cotton balls to keep it separate from the seeds, then pop the stopper in the jar, and wrap or cover it in something opaque to protect the precious contents from light. This important factor will preserve your seeds for over a year and longer if refrigerated.
Those little pouches that you find in the packaging for all manner of items, from electronics to sports shoes, make for an essential ingredient in the seed storage game. Typically containing silica gel, a substance that absorbs moisture, these sachets are your chief ally for limiting mold growth and reducing spoilage inside sealed containers. You can buy desiccant packs online and are cheap to buy in bulk. If your seeds are stored in plastic containers, mylar bags or a plastic bag – these may be essential.
Other Tools to Consider
For those really serious seed collectors, you may want to track and monitor your seeds’ climate. This can be achieved using something relatively cheap like the Govee range of sensors which can be linked to your phone via Bluetooth or your network via Wi-Fi to allow tracking of your seeds’ conditions without having to disrupt them.
Safely Store Cannabis Seeds
Ensure your storage method meets the necessary criteria beforehand, and as long as it’s clean and insect-free, it should stand you in good stead, especially for short-term storage. Resist any temptation to open your seeds to check on them or add more seeds – if you have more seeds to store, use a new container every time, or you run the risk of creating the kind of fluctuations that cause problems for your existing seeds.
While research typically yields differing opinions over the optimal temperature and humidity levels for storing seeds, one thing is clear: consistency is key. Whatever you decide upon, your main objective is to keep that as consistent as possible in the most ideal conditions. It is change that the seed recognises the most. While it’s vital to keep light out of the storage environment and keep temperature and humidity levels low enough to avoid germination – but not so low as to damage the seeds – it’s crucial to avoid fluctuation of any of these variables.
How Long can you Store Cannabis Seeds?
Well, if you follow all of the above it could be a very long time indeed. Marijuana seeds, ideally though, should be germinated sooner rather than later. If kept at room temperature in an airtight container, the answer is around 16 months (although this is debated). However, if they’re vacuum-sealed, and kept in a dark place without fluctuations in temperature, it could be years. The lifespan of a seed depends on you.
Avoiding temperature fluctuations, excess moisture and keeping them in a storage container that meets that criteria means your seed germination should be easy.
Like all living organisms, source quality places a huge part. As a seed bank that prides itself on producing weed seeds that produce cannabis plants of excellent quality – we test each strain for its vigour and resistance, all the way from seed to harvest.
We’ve written a total guide on the length of seed storage here:
Consultation for this article by Dr. Gary Yates of Pharmaseeds