How Long Do Weed Seeds Last?

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 weed seeds that are over a decade old.

Others argue that marijuana seeds are no longer viable after a couple of years.

Most seed banks advise growing a healthy seed 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 guide on How to store weed seeds.

If you keep your weed seeds in a cold, dry, and dark environment, you should be able to germinate your seeds for up to a year. Storing seeds in direct sunlight or damp, humid conditions will result in seeds that will not be able to germinate anymore within a year.

Cracked marijuana seeds or crushed cannabis seeds will also fail to sprout into seedlings, so it is vital to keep unused seeds in a safe container.

Besides protecting yourself from dealing with cracked seeds, you have to make sure to store seeds in a relatively dry environment. Those little sachets of silicon balls that you find in new bags are very useful at absorbing any moisture that could lead to dampness and mold.

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

Older seeds are less predictable than younger seeds. The older the marijuana 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 organized 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 color 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 cannabis seeds is in a dry, completely dark container in a cool place such as a refrigerator or somewhere with a constant low temperature. While the success rate does go down in the years, it's far from impossible to germinate cannabis seeds after several years of optimal storage.

How to rescue old marijuana 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 old cannabis seeds in a cup of water with a few milliliters 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 (72° F) 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 allow water to permeate.

Here's a good technique, as you don't want to overdo it. Get a piece of the finest grain sandpaper, roll it up into a small tube with a rough surface on the inside, and stick it together with some tape. Pop the cannabis seeds inside and use your hands to cover the ends. All you have to do is gently shake for a few minutes.