How to germinate old cannabis seeds

How to germinate old cannabis seeds
Luke Sholl

Although prime cannabis seeds are typically younger, old weed seeds may still be viable! However, you have to go about germinating them differently, as time tends to harden these magic beans. Learn how to germinate your old cannabis seeds to achieve a bumper harvest.

If stored properly, marijuana seeds can remain viable for many years. However, the longer you keep them, the harder it is to make them sprout. More often than not, you’ll have to use different hacks to successfully germinate old cannabis seeds. We’ll teach you how, but first, let’s see what conditions make cannabis seeds come alive in the first place.

Moisture Is Key To Cannabis Seed Germination

If you want to successfully germinate cannabis seeds—whether fresh or old—you must satisfy the following conditions: warmth, darkness, and moisture. The first two are important, but it’s moisture that causes the dormant embryo inside to begin its life cycle.

That’s why it’s so important to store cannabis seeds in a dry place—so they don’t germinate prematurely, become mouldy, or rot.

The problem with very old seeds is that their outer shell dries out over time, and it gets more and more difficult for water to penetrate them. As such, you, the grower, must take some steps to facilitate this process.

Best Methods for Germinating Old Seeds

So, the question of how to germinate old cannabis seeds translates to: how do you help moisture get inside your old seeds? The obvious first choice is to pre-soak them before germination.

1. Place Old Weed Seeds in a Glass of Water

With old weed seeds, your favourite germination technique, such as the paper towel method or the straight-into-the-medium method, may not work. The reason is simple—these techniques don’t provide enough moisture to penetrate the hardened outer shell.

Instead, take a glass of water and throw your seeds into it. Twelve hours will be enough for the shell to soften a little and the water to finally get inside and wake up the embryo. Don’t forget to check the seeds regularly. As soon as they crack and the taproot appears, you should take them out. Seeds are living organisms and they need oxygen. Leave them submerged for 24 hours or more, and they may drown.

In most cases, you can simply use drinking water, but germinating old cannabis seeds may require some further tweaking. Some growers use carbonated water because the presence of CO₂ supposedly helps water penetrate the seed shell. Hydrogen peroxide (a few drops per glass) is said to have the same effect. You may also consider adding some biologically active compounds, such as:

  • Superthrive (one drop to a glass of water)
  • Nitrozyme (10ml/L)
  • Humic and fulvic acids (10ml/L)
  • Rooting hormones

The problem with these stimulators is that you never know the correct dosage. The information shared on marijuana forums is anecdotal, and legitimate studies have only been performed on other crops. So, if you decide to use any of these additives, do some research or ask other growers, and always err on the side of caution.

1. place old weed seeds in a glass of water

2. Use the Scarification Method

Another method of making the outer shell more penetrable is scarification, and the most straightforward way to do this is to use sandpaper. Take a matchbox and line its inside with sandpaper, or roll a piece of sandpaper into a tube. Then, place the seeds inside and shake them for a minute.

This will be enough to make a lot of tiny scratches on the protective outer layer of the shell, allowing moisture to get inside much more easily.

3. Crack Your Weed Seeds

Some people buy a special cracking tool for old cannabis seeds. This simple contraption applies mild pressure on a seed until an audible crack is heard. Others simply bite on the seed—ever so gently—until they hear it crack.

Please keep in mind that this particular method of germinating old cannabis seeds is a bit risky, as are the techniques described below.

4. Remove the Ridge

The ridge is quite prominent on the seed. It connects the two halves of the outer shell, and when the embryo pushes against them, it’s this ridge that cracks. However, in older seeds, it’s too hardened by time and needs to be cut off.

Use a sharp knife to cut the whole length of the ridge, on both sides. Be sure not to cut too deep and damage the embryo.

4. remove the ridge

5. Surgically Open the Seed

This procedure is similar to cracking because you’re forcefully opening the seed—not by applying pressure this time, but by using a sharp knife. Please consider this a last resort—suitable only when all else fails.

Germinating Old Cannabis Seeds Requires Patience

Please note that, besides poorer germination rates, old cannabis seeds also take longer to sprout. So, how long exactly does it take to germinate old cannabis seeds? While fresh seeds usually germinate in 1–3 days, older beans routinely take as long as 7–10 days or even more. So, be patient, and, if the seed remains dormant, try one of the tricks described above—starting with the least invasive one. It’s also best to try them one after another, as opposed to all at the same time.

Avoid Putting Old Cannabis Seeds Straight Into the Medium

Personally, we like germinating weed seeds in soil, but when you’re dealing with old ones, it’s best to regularly check on their progress. This will spare you a lot of nail-biting, because you never know how many days this will take. So, check the quality of your seeds, and, if you have any doubts, choose a more “visual” method, such as germinating in a glass of water.

Luke Sholl
Luke Sholl

Fascinated by the wellness potential of nature, Luke has spent over a decade writing about cannabis and its vast selection of cannabinoids. Creating, researching and writing content for Cannaconnection, alongside several other industry-related publications, he uses strong technical SEO skills and diligent research to bring evidence-based material to thousands of unique visitors.