Question: How long do weed seeds last?

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The answer to the question ‘how long do marijuana seeds last?’ is one that is hotly contested by many growers. Some claim that, if stored correctly, it is possible to grow cannabis from seeds that are over a decade old. Others argue that marijuana seeds are no longer viable after a couple of years. Most seed banks advised growing seeds within a year of purchase. So who is right? As many growers find they have a few old seeds lying around or newbies may have been given some spare seeds by friends of the family and are interested in growing weed for the first time, it is a question that is worth answering.

There is no denying that the right storage is important, and you can read more about how to correctly store marijuana seeds in our useful blog here. If seeds are stored in direct sunlight or damp, humid conditions, it is unlikely that they will germinate if they are over a year old. Seeds that are cracked or crushed will also fail to sprout into seedlings, so it is vital to keep unused seeds in a safe container. Those little sachets of silicon balls that you find in new bags are very useful at absorbing any moisture that could lead to damp and mould.

Why is it important to know the age of cannabis seeds?

Older seeds are less predictable than younger seeds. The older the seed, the lower the chance that it will successfully germinate. Even if they have been carefully stored according to all the expert advice, the time it takes for them to germinate varies hugely. If you are planning to cross your own plants and develop your own strains, it is essential to get organised and to record the age and variety of your weed seeds to avoid wasting time in the future.

Do the seeds of some cannabis strains last longer than others?

No, although there is a considerable variation in the appearance and colour of cannabis seeds, the outward appearance gives little indication to the health and viability of the strain. As long as the seed’s outer casing is smooth and intact, the inner genetic material will be protected.

That said, very elderly cannabis seeds sometimes feel weaker when one gently squeezes them. Throw them away if the husks split open and release the dusty contents – these are seeds that are obviously no good. The best way to store marijuana seeds is in a dry, completely dark container in a cool place such as a refrigerator or somewhere with a constant low temperature. You can definitely successfully germinate cannabis after several years of optimal storage.

Related article: how to store weed seeds

How to rescue old seeds?

If you have only kept the seeds for about eighteen months or less, they should be fine to use. After this time, germination may be more complex because older seeds have harder shells, so water used to soak them will take longer to penetrate. You should, therefore, place the seeds in a cup of water with a few millilitres of hydrogen peroxide and leave for 24 hours. This will soften the shell and facilitate the infiltration of the water.

Make sure that the water is lukewarm – about 22° C and ensure that the glass is kept away from light sources. Keep a close eye on the seeds during this time, as if they start to open, you will need to take them out quickly, or they will ‘drown’.

Another useful trick to encourage the germination of old seeds is to scrape off the seed’s outer layer with sandpaper. This creates micro-abrasions that similarly allows water to permeate. Here’s a good technique as you don’t want to overdo it. Get a piece of the finest grain sandpaper and roll it up into a small tube with the rough surface on the inside and stick it together with some tape. Pop the seeds inside and use your hands to cover the ends. All you have to do is gently shake for a few minutes.

Related article: how to germinate marijuana seeds?

Final thoughts

Although it’s always good to use up old seeds, the best way to achieve a satisfactory harvest of home-grown weed is to invest in some high-quality seeds. When you buy cannabis seeds online from a reputable purveyor such as Weedseedsexpress is the best way of guaranteeing fresh, young seeds. You also gain peace of mind from knowing that your weed seeds contain the finest genetics to deliver top-quality buds when the time comes to harvest.

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