Keep the water warm, but not too hot. Aim for around 22°C. Avoid direct sunlight, and keep an eye on the glass. Do not soak seeds for prolonged periods, more than 24 hours can deprive them of oxygen and make them drown.
As cannabis seeds age, their protective outer shell hardens and prevents water from passing through. Unless the tiny, dormant embryo that lives inside the shell detects moisture, it doesn’t know that the conditions are right to sprout. As a first step, pre-soak your old cannabis seeds for about 12 hours to see if that does the trick.
The seed’s shell is made up of two pieces, with a seam going all around. The side that’s raised more than the other is the ridge. A hardened ridge can make it difficult for the seed to open. To remove the ridge, run a sharp blade along the ridge on both sides. Handle gently and it should come off without damaging the inside of the seed.
Scarification, or scuffing the shell, can also help water pass through an older seed’s tough outer shell.
The older a cannabis seed gets, the harder it is to pop. But hard doesn’t mean impossible. If you’ve been saving your seeds for a rainy day and it finally started pouring, these tips could help you get most, if not all, of your old beans to germinate.
Before you start, it’s important you remember the following:
Try dropping your old seeds into a glass of sparkling water. The CO₂ in the water should help the seeds absorb more moisture, encouraging them to sprout. You can also add some fulvic acid to the water to help break down the shell of your seeds. You’ll only need about 2.5ml of acid for a glass of sparkling water (roughly 250ml).
TRY SCARRING YOUR SEEDS
If you’ve tried all our tips above and still haven’t managed to germinate your seeds, it’s likely they are beyond the point of return. To avoid having the same problem next time, here are some tips to help you store your seeds:
If this isn’t enough, you can try carefully (and very gently) using a sharp knife like a Stanley blade to remove the ridge running along the middle of each seed. This should expose the inside of the seed a little, helping it absorb moisture and, hopefully, giving it a better chance of germinating.
Sometimes, it’s best to leave Mother Nature to work her magic on your old seeds. Try scarring your seeds a little as we showed you earlier, then let them sit in carbonated water overnight. Next, prepare a small nursery pot with some high-quality soil. Make a small hole in the middle of the pot with your finger, roughly the depth of your fingernail. Drop your seed inside the hole and cover it. Moisten the soil and keep your pot in a warm place with indirect sunlight—a windowsill works great.
But you must be careful: the liquid must not be cold, but rather at a temperature of around 22° C. And you must keep the container away from major sources of light. During the 24 hours that the seeds are there you will have to keep a very close eye on them in order to remove them quickly if they open, so they don´t “drown.”
There are growers who prefer their seeds to germinate directly in the soil. In this case, in addition to ensuring that you have light and well-nourished soil, you can choose to dilute 10 ml (a teaspoon) of fulvic acid per litre of water, and use it to water the site where you have planted the seed. Another option is to use slightly carbonated water, as the additional CO2 will help the liquid penetrate the seed, causing it to germinate. It is also possible to use enzymes or germination enhancers, designed to help seeds open and develop in those first stages.
Hydration to trigger germination
For those beginning with the glass of water, the second step would be to move the seeds, after 24 hours, to the wet paper towels. Germination normally takes between 48 and 72 hours, and, in the case of old seeds, can last up to 5 or 6 days, or even weeks. Therefore, transferring the seeds to wet paper gives you more peace of mind, as you are dealing with less water and, if they open, they will not quickly drown.
First, you have won half the battle if you were careful with the original storage. Seeds must be kept in a cool, dry place. Therefore, the best option is to store them in refrigerators at a temperature between 6 and 8 degrees Celsius, and with relative humidity levels between 20% and 30%. And sheltered from light, of course.
For example, you can scrape off the outer layer of the seed with a little sandpaper, creating micro-abrasions that should let some water in. So you don’t overdo it with this scraping we have a little trick: roll up a piece of very fine sandpaper, with the rough side on the interior, and secure it with tape. Place the seeds inside and cover the openings with your hands. Then just shake it for a couple of minutes and the sandpaper will do its job. Another more risky option is to use a knife to cut the seed transversely, ever so slightly, which will help the water penetrate the shell.