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How to Germinate Old Cannabis Seeds: 6 Methods to Try

Last updated: 13 November 2023

how to germinate old cannabis seeds

As cannabis seeds age, they become increasingly difficult to germinate. However, difficult doesn't mean impossible! If some of your seeds have become dry and crumbly and you're not sure they will pop, these tips can give you a good chance of sprouting most, if not all, of your older seeds. So, let’s dive in and find out how to germinate old cannabis seeds properly!

Is It Even Possible to Germinate Old Cannabis Seeds?

If you store weed seeds correctly, they can stay good and healthy for a long time. But the more you keep them, the more difficult it becomes to get them to start growing. If the seeds look gray and shiny, they're old and probably dried out. Old seeds can also sometimes split or crack. Any seeds that look pale, light brown, gray, split, or cracked are considered defective.

However, it's possible to save some of them, and they may still grow into plants that produce buds. Usually, you'll have to try different tricks to get old weed seeds to germinate. But keep in mind that, sadly, there are no guarantees that your old seeds will pop if you use these methods.

6 Methods to Germinate Old Seeds

Germinating old weed seeds can be a real challenge, but it’s still worth trying. Their outer shells get tough and stubborn as they age, making it even harder to sprout them, but don't fret! Let's take a look at the methods you can use to bring those oldies back to life.

Method 1: Using Paper Towels

germinate old cannabis seeds using paper towels

This method for sprouting seeds is so popular because it works really well. Although it might not be enough for your old seeds to pop, it's still easy and safe, and thus worth trying.

The paper towel method is the go-to method for newbies in growing – it's so simple that you hardly have any chance to mess up. Now, let's dive into the whole process one step at a time.

  1. Grab a salad plate and put two sheets of paper towels on it. If they're thick, one layer will do the trick. Otherwise, you might want to slap on an extra layer.
  2. Next, wet the paper towels a bit. The quality of water is crucial: it should be drinking water (non-carbonated and non-mineralized), rainwater collected in a clean container, or distilled water. Make sure the pH level is somewhere between 5.5 and 7. After wetting the towels, put your seeds on them and then cover the seeds with two more sheets of wet paper towel.
    Note: Steer clear of using tap water, even if you leave it for 24 hours to get rid of the chlorine.
  3. Double-check that you haven't poured an excessive amount of water. It shouldn't spill over when you tilt the saucer – that would be way too damp. If you happen to have a plant mister, 2-3 ample sprays will suffice. If you went overboard with water, just give the towels a little squeeze to get rid of the excess.
  4. Finally, put another plate on top and hide it all away in a cozy, dark cupboard. Make sure the towel doesn't dry up and try to keep the temperature between 22-27°C (72-80°F). Keep an eye on whether the seeds have cracked. Just don't get too excited – take a peek inside the paper towel after 12-24 hours the first time, and then check every 12 hours after that.

Tip: Instead of using a paper towel, you can stick each seed between two cotton pads – they'll be easier to open when it's time to take out the seed. Instead of saucers, you can also stash your seeds in an airtight container or a ziplock bag to make sure the towel/cotton pads keep the moisture.

Using paper towels or cotton pads is the easiest and most promising way to sprout old seeds. However, there are also a few other methods to consider – you can find them below. Just remember, these alternatives do come with a bit more risk. Check out our article on how to germinate marijuana seeds properly for even more insight into the process.

Method 2: Pre-Soaking

pre soaking old cannabis seeds

You can place the seeds in a glass of water before sticking them in a rockwool cube, peat pot, rapid rooter, or any other germination medium. To up your chances, use fizzy water and/or toss in some of these things that help with sucking up water: gibberellic or fulvic acid, hydrogen peroxide, nitrozyme, etc.

Here's the catch with these boosters: you never really know how much you should use. The info you may find on weed forums is just people's stories, and legitimate studies have only been done on other plants. So, if you decide to use any of these germination boosters, go easy.

Make sure the water is warm, but not too hot – around 22°C is enough. You can also give carbonated water a shot – it won't hurt. Don't let the sunlight directly hit the seeds, and be careful not to soak them for too long, as more than 20 hours can cause a lack of oxygen and make your seeds drown. Pre-soaking them for 12 hours should be sufficient to slightly soften the seed shell and get the water inside to activate what's within. Remember to regularly check the seeds, and once they crack open and the taproot starts to show, remove them from the water.

Method 3: Scarification

old cannabis seeds scarification

Another cool trick is to make the outside of the seed easier to penetrate by scuffing it up. All you need is some sandpaper, a matchbox, and a few seconds of shaking. Line the inside of the matchbox with sandpaper or roll a piece into a tube. Toss the seeds in, give it a good shake for about 30-60 seconds, then take them back out. This little trick will create a bunch of tiny scratches on the hard shell, making it easier for water to seep in.

Method 4: Cracking

cracking old marijuana seeds

Some growers purchase a cracking tool for their old weed seeds, which applies a bit of force on the seed until you hear it crack. Alternatively, some peeps just give the seed a little nibble until it makes a cracking sound. However, be aware that this method of getting old seeds to sprout comes with its fair share of risks, just like the others mentioned below.

Method 5: Removing the Ridge

removing ridge from old weed seeds

The ridge on the seed is really noticeable. It links the two parts of the outer layer, and when the little plant pushes against it, that's what causes it to crack. However, with some older seeds, the ridge becomes so hard and tough from being around for so long that it must be sliced off. You can use a sharp knife to cut all the way along the ridge on both sides. Just be careful not to go too deep and hurt the embryo. Taking off the ridge not only makes it easier for the seed to pop open but also helps water penetrate the seed.

Method 6: Slicing

slicing old cannabis seeds

This method is a bit of a gamble because it could end up destroying as many seeds as it saves – and you're not a surgeon, after all! However, if you want to go all the way in an attempt to make your oldies pop open, try the following. Take the seeds out of any wet conditions and let them dry completely. Then, cut into the seed along the seam with a clean scalpel and crack it open a bit. Now you can give it another shot at germination.

Always Keep an Eye on Storage Conditions

You won't have to apply all these methods to germinate really old cannabis seeds if you store them properly. It's important to keep them cool and dry, so the smartest thing to do is keep them in the fridge at a temperature of about 6-8 °C. Of course, you should also make sure they're protected from light.

To make all this happen, you can use an airtight container or canister, or even an opaque plastic bottle. Besides the seeds themselves, throw in some little silica gel pouches to soak up any extra moisture. As for the best spot in your fridge, the crisper drawer is a good pick since it's a bit warmer than the rest.

One last tip: if you store several strains in different bottles, it’s a good idea to label them so that you won't have to open them to see which is which when you decide to plant.

In the future, think about ensuring proper storage conditions and growing your seeds earlier so they don't end up going bad. Weed seeds can be pretty pricey, so it's a waste in every aspect to just let them get old.

Wrapping Up

Here's one last piece of advice. Besides the fact that old marijuana seeds don't sprout as well, they also take longer to start growing. So, how much time does it actually take for old weed seeds to pop? Usually, fresh seeds sprout in 1-3 days, but old ones can sometimes take up to 7-10 days or even 2-3 weeks to germinate. So just hang in there, and if the seed doesn't start growing, try one of the tricks we mentioned, beginning with the easiest and least harmful one. It's also better to try these methods one by one instead of all at once.

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