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How Long Do Cannabis Seeds Last?

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.

Understanding the Key Elements of Seeds 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.

Understanding Cannabis Seeds

Cannabis seeds are similar to any other type of seed used to produce plants. They’re hardy-looking things, but they have a shelf life. They’re also susceptible to environmental changes – too much fluctuation in any direction can cause them to spoil. An undesirable extreme change in temperature or humidity at the wrong time (during storage) will put paid to your seeds. Light is the other main naturally-occurring variable you should protect your marijuana seeds from.

It’s important to remember that your seeds are dormant before germination but very much alive. For this reason, it’s best to treat your cannabis seeds with a degree of care and common sense. Unless you’re about to germinate, make sure your seeds ‘sleep’ in ideal conditions.

Seeds

How the Main Variables Affect your Cannabis Seeds

It’s one of the classic storage instructions on packages for all manner of products – store in a cool, dry, dark place. As mentioned above, high temperatures and moisture levels tend to cause things to spoil, especially if they contain natural ingredients.

Light, heat and moisture all signal to your seeds that it’s time to sprout, and each of these variables affects your seeds differently. Exposure to any of these elements will cause your seeds to expire unless they’re well protected.

Light

When you store cannabis seeds, it’s essential to keep them away from light. For example, don’t be tempted to throw a handful in a baggie and keep them in your grow room. Keep your seeds in their original packaging, or transfer them to an opaque, airtight container. Something such as an envelope or a blacked-out mason jar is perfect for room-temperature storage. Keeping seeds well-shielded will prevent them from absorbing any light before your planned germination time.

The shells – those hard, waxy coatings on seeds – offer a degree of protection against light. But while cannabis plants love light, cannabis seeds do not. In nature, cannabis seeds fall from the plant towards the end of the year when daylight levels are reduced. They then sit beneath a light covering of soil until the following spring when they could naturally germinate and bloom. It helps to think about the natural cycle when storing cannabis seeds. Keep them dormant until you decide you want them to germinate.

Humidity

If you want to store your cannabis seeds long-term and retain their viability, it’s imperative to keep humidity levels under control. Moist, humid conditions are key ingredients in the seed germination process. If you expose the seeds to high humidity levels too soon, they may begin to germinate on their own. You don’t want to store your seeds at too low a humidity either – that can bring a different set of problems entirely. Here’s how humidity levels can affect seed viability:

75%-100% humidityHumidity levels are too high, and the internal moisture content will cause the seeds to effectively drown
40%-60% humidityThis is the optimum humidity range to germinate seeds, so store seeds below this range
20-30% humidityThis is a relatively sweet spot where humidity is sufficient to store seeds.

Not too high, not too low. It would be best if you aimed to keep your seeds at this humidity level
Below 20% humidityThis is too dry and can cause issues such as sweating, drying out and fungi.

These figures are a rough guideline, as risks vary slightly depending on storage method and container type. Still, they serve as an excellent approximate rule of thumb for humidity levels. Excess moisture will soften the seed’s outer shell and cause the taproot to emerge. If you’re not actively germinating that seed, it’s spoiled.

Monitoring Humidity Levels for Cannabis Seeds

Keeping tabs on relative humidity levels is reasonably straightforward. You can pick up a humidity meter on Amazon.com, and while they can vary in terms of features and cost, there are budget humidity meters which are inexpensive and still do the job.

How to Control Humidity Levels for Cannabis Seeds

Start by choosing the storage container wisely and then the environment. Use an opaque tin, plastic container or the original packaging, so long as it’s a container that seals tightly. After that, it’s a question of choosing the right environment to ensure humidity is right for safe storage. Toss in a desiccant like a silica gel pack for extra help.

Storing Seeds Shorter-Term in a Room

If your planned storage spot is in a room that’s prone to condensation on the windows, pick another location. Condensation is a good indicator that room humidity is too high, and this will harm your seeds quickly. Choose wisely – laundry rooms or bathrooms naturally make bad spots to stash seeds due to high heat and humidity levels. A living room drawer or a dark cupboard in an area that doesn’t see too many extreme temperature fluctuations is ideal.

Opening windows and vents will help keep humidity levels nearer the sweet spot. If your storage space is prone to humidity, it may be worth investing in a dehumidifier. It’s impressive how much moisture these can pull out of the air after a few hours, so it’s good to know that some devices can decrease room humidity fast.

Storing Cannabis Seeds in the Refrigerator

This is a fairly common strategy for storing cannabis seeds. Seeds are placed in a suitable container and kept safely in the refrigerator for years, retaining great viability rates. The lower temperature of the fridge makes an ideal environment for preserving seeds, working in a similar way to storing food in your refrigerator. At low temperatures, the cellular biochemistry of the seed slows down, and the seed remains viable for years. This is why a cool place is always best for storing seeds.

Storing Cannabis Seeds in the Freezer

It’s certainly doable, but it’s arguably not necessary. Storing your cannabis seeds in the correct container in a freezer will undoubtedly extend the viability of those seeds. But is it a gamble worth taking? Sure, if you have many big projects planned and many seeds to store. In most cases, though, storing your seeds in a refrigerator is just as helpful and probably less risky. Some collectors store vintage seeds in a freezer for long-term safety, but this isn’t a necessity for most of us.

The Ideal Temperature Range for Safe Seed Storage

If storing your seeds in a cool, dry place, pop them in a drawer well away from heat sources. This quick and easy way to keep seeds stashed will ensure a good degree of viability in most cultivars. The main thing is to keep the temperature low and away from the risk of temperature changes. The lower the temperature, the longer you should effectively be able to store your seeds safely.

If storing cannabis seeds in the fridge, make sure your fridge can maintain a steady temperature of between 4°C and 6°C. This will ensure safe long-term storage. In both cases, it’s best to store seeds in a suitable container, especially if you’re storing them in a fridge. The lower temperature of the fridge demands a little more protection for your seeds. An opaque tin or container with a seal that is air and watertight is your best friend in this instance.

Cultivars

Not all seeds are created equal. If you’ve grown different cannabis strains from seed, you’ve probably noticed that some seeds are larger or more resilient than others. Some batches will occasionally contain failures, but most seeds should store long term without any hassle. Not every seed in a batch will necessarily respond the same way, though. In a bag of ten seeds, you might find a couple don’t germinate, and while this is annoying and unfortunate, it’s sometimes just the nature of the genetics.

Hypothetical Case Studies

Customer 1 is a hobbyist cannabis grower. He buys a couple of bags of seeds from Seedsman during a promotion, intending to plant some now and store others for later. Customer 1 can safely store his surplus seeds in the original package or transfer them to a suitable container. He can seal it and place it in a dark, dry cupboard or drawer, away from any heat source. Using this method for short-term storage, Customer 1’s cannabis seeds should easily remain viable for between three and five years.

Customer 2 is a commercial cannabis grower. She buys her cannabis seeds in bulk, but only ever has a dozen plants growing at any given time. In this situation, she can safely store her surplus seeds in an appropriate container inside a refrigerator. She sets her refrigerator to maintain a steady temperature between 4°C and 6°C. Using this storage method, Customer 2’s cannabis seeds should easily remain viable for five years or more.

Customer 3 is a well-known seed bank. They are looking to preserve certain genetics long into the future, and store those particular older seeds in a freezer. They ensure to keep seeds in the correct containers and handle them with care at every stage. Aware that the frozen tissue inside the seeds becomes delicate and at risk of shattering, they treat seeds with the utmost caution. These steps should see their seeds retain a high rate of viability for decades.

Having Quality Genetics Helps

The answer to the question, then, is seed viability is largely dependent on how you store your seeds. By knowing how long you want to keep your seeds, and storing them accordingly, you can take the proper steps to ensure they will remain viable for as long as you need them to. Remember that seeds contain living matter, and there’s always a percentage risk of failure. This is true regardless of how well you handle and store them. By buying cannabis seeds from a top-quality seed bank like Seedsman, you ensure greater quality of genetics and stack the odds of a high germination rate in your favour.

Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.

This post is also available in: French

Duncan Mathers