16 reasons your cannabis seeds aren't germinating
It can be really frustrating to prepare a grow space, plant your seeds, and then wait, watch, hope... only to find that nothing happens. But there are many reasons that cannabis seeds might not germinate, and most of them can be solved or prevented.
Germinating cannabis seeds can be a nerve-wracking experience. With essentially all other stages of a plant’s life cycle, you can observe the specimen and take cues from the plant itself. However, when you’re germinating seeds, you’re basically waiting around for something, anything, to happen. And if it doesn’t, it can be very difficult to diagnose what’s gone wrong.
With that in mind, this article will outline 16 likely reasons that your cannabis seeds haven’t germinated, and what, if anything, you can do to solve it.
How to know if cannabis seeds are germinating
Figuring out whether your cannabis seeds are germinating shouldn’t be too difficult. If the seed opens and something pops out (two green cotyledon leaves and a taproot), then your seed has germinated!
If you’re germinating in soil or some other substrate, then you might only know your seeds have germinated when the cotyledons appear, as you’ll never see the taproot. If you germinate in a glass of water or a damp paper towel, however, then you’ll see the seed open and expose all parts of the shoot’s anatomy.
If the seed remains closed, then it hasn’t germinated.
What’s more difficult than figuring out if your seed has germinated is figuring out whether or not your seed is going to germinate—or if it’s a dud.
How long do cannabis seeds take to germinate?
On average, a cannabis seed should take 4–10 days to germinate. Anything in this range is normal and totally healthy. Germination can sometimes be faster than this, while certain seeds (especially old ones) might take longer, with some taking upwards of 20 days.
However, in the vast majority of cases, good-quality seeds in the right conditions should sprout within the above-mentioned time frame, giving rise to young cannabis seedlings.
Why aren't my cannabis seeds germinating: 16 reasons
Sometimes seeds fail to pop, and there are many reasons for this. You might wonder what to do if your cannabis seeds don’t germinate, and the answer is, as always, it depends!
Though it may be that the seeds are duds, it may well instead be that there’s some environmental problem that’s well within your control to fix. If you identify this as the case, then your grow isn’t over yet. Below we’ll look at what those problems could be.
1. Too wet
First off, it may be that the growing medium is too wet. Now, if you’re germinating your weed seeds in a glass of water, then this probably isn’t the problem. But if you’re germinating in soil, or some inert media, then you want it to be damp and humid, but not too wet.
Seeds in a very wet substrate might take longer to germinate, or they might not germinate at all. If you think the substrate is too soaked, perhaps the best choice at this stage is to replant your seeds and start afresh.
And be careful; soaking-wet soil makes the chance of certain pathogens appearing much higher, which can lead to conditions such as damping off—which will kill your plants very quickly.
2. Too dry
On the other side of the coin, conditions might be too dry. Cannabis seeds need damp soil and a relative humidity of around 70–90% in order to germinate properly.
If you try to pop seeds in a dry or mostly dry substrate, the chances of them germinating are very low. You should water the soil until it's comfortably damp, then cover the seed to stop it from drying out while it is trying to germinate. If the soil begins to dry out during this process, then water it lightly.
3. Poor water quality
Dirty/contaminated water might also stop cannabis seeds from germinating. Yet, in most cases, poor water quality is unlikely to be the culprit of seeds staying stubbornly shut, and you should definitely look for potential causes elsewhere first.
However, if you can’t find another issue, or you know your water is particularly dirty or high in certain minerals, then this might be the cause.
4. Too little oxygen
Seeds need enough oxygen to germinate. In fact, cannabis plants in general like well-aerated soil. At the germination stage, seeds need oxygen to metabolise before photosynthesis takes over. Whether growing indoors or outdoors, you should use an airy, loamy soil to germinate cannabis seeds.
The same goes for other growing media—ample oxygen is essential to healthy growth at all stages of development.
5. Too much oxygen
A highly oxygenated environment might also cause problems for germinating cannabis seeds. In a soil grow, this is pretty much impossible. But in very specific hydroponic setups, this could become an issue.
6. Too many nutrients in the soil
If the soil is packed with nutrients, especially synthetic nutrients, this can be toxic to cannabis seeds and stop them from germinating.
If you’re using high-quality soil for germination, then you shouldn’t need to add any nutrients to the soil until well into the vegetative stage, or even later in some cases. Good soil comes packed with plenty of nutrition to see plants through the first stages of their life cycle.
If growing in an inert medium, however, then you will need to add nutrients. Especially at these early stages, you should be very careful about both the quality and quantity of nutrients you add. Often, less is more.
7. Not enough space
To germinate healthily, seeds need ample space. To achieve this, you should sow them at least 5cm apart so they have space to open and begin developing. Setting up the perfect grow space is necessary from the very beginning, and you’ll be grateful for it.
Were you to just throw a handful of seeds into some soil, then it is likely that some would sprout and others wouldn’t. So while viable, it is not the most efficient method of germinating seeds.
8. Low temperatures
Cannabis seeds like warm temperatures to germinate, with around 20–22ºC being ideal. This is why many growers germinate indoors, even if they intend to take their plants outdoors for most of their lives.
If temperatures drop too low, then you can expect delayed or entirely stalled germination. At temperatures below 12ºC, some seeds might eventually sprout, but many likely won’t.
9. High temperatures
Likewise, if temperatures are too high, then seeds will also struggle to germinate. Depending on the strain, seeds will germinate under slightly different conditions. However, few are predisposed to germinate under the intense heat of summer, so keeping temperatures at around 20–22ºC is good practice.
Some fluctuation in temperature is unlikely to cause too many problems, but sustained heat can send seeds the wrong signals, and keep them from opening.
10. Damping off
Damping off is a name given to a condition that afflicts cannabis seeds and seedlings. Mostly, it is known for causing seedlings to wilt and die. But it can also affect seeds and stop them from germinating at all. This is known as pre-emergent damping off.
Though it can occur in any setting, this is more common when germinating seeds in a greenhouse, where conditions are wet and humid—just perfect for the fungi that cause damping off.
If conditions are cool, wet, and humid, then it may be that damping off has occurred. The bad news is that the pathogens responsible will kill the seeds, so they will no longer be viable. If you expect damping off to be the cause, then you should carefully dispose of seeds, soil, and containers to ensure that the condition does not spread to other seeds or plants.
11. Seeds were handled with bare hands
Bare hands might transmit any number of pathogens to cannabis seeds, which could kill them and stop them from germinating. Therefore, it’s good practice to wear clean gloves, or at the very least thoroughly wash your hands before handling seeds. Some growers choose to handle seeds with sterilised tweezers, as this can help with precision anyway.
Identifying this as the problem can be very difficult, as all you have to go on is whether you touched them with bare hands or not. You’ll never really know if this is the cause, so you should rule out more treatable causes before leaving your seeds for dead.
12. Low-quality seeds
High-quality seeds have a higher germination rate compared to low-quality seeds. In fact, the best breeders will batch test their seeds to ensure that almost every seed sold is capable of germinating. Germination rate doesn’t really relate to the strain or type of seed (e.g. feminized vs regular), but simply the quality. For example, you can get both good and bad-quality OG Kush seeds.
If you’ve bought high-quality seeds and very few are germinating, then you can safely assume the problem is not the seeds. If, however, you’ve bought low-quality seeds and many don’t germinate, then they might just be bad seeds. Knowing where to source your seeds will improve germination rates.
13. Old seeds
While seeds can remain viable for many years, the older seeds get, the longer they will take to germinate. Eventually, they won’t germinate at all.
Generally, you should try to use seeds within a year or two of them being taken from the mother plant, for best results. But if you wait longer than this, all is not lost. Knowing how to germinate old cannabis seeds can get the process moving, and make the chances of success higher.
Will fresh cannabis seeds germinate?
Yes, you can germinate fresh cannabis seeds so long as they are sufficiently mature. If you take seeds from a female cannabis plant that isn’t fully mature, then you probably won’t be able to germinate them. However, if you wait for the plant to die naturally, then you’ll know it has successfully finished producing its seeds, and they’ll be ready to create the next generation.
14. Seeds stored incorrectly
If you’ve stored your seeds incorrectly, then this might stop them from germinating later on. Cannabis seeds should be stored in a cool, dark, and dry environment. If they get too hot or too cold during storage, this might kill them off.
But the biggest problem comes from moisture. Moisture triggers germination in cannabis seeds, so if they are stored in a moist environment, they might begin to sprout early. In some cases, this will be obvious, as they’ll be open. However, sometimes the process might start enough to cause damage, but stall before it becomes obvious to the eye.
As such, learning to store cannabis seeds correctly is very important.
15. Seeds were eaten
Indoors, this is unlikely to be a problem. But outdoors, some critter might come along when you’re not looking, dig your cannabis seeds up, and eat them. In this case, you can be sure that they won’t germinate.
It’s easy enough to tell if your cannabis seeds have been eaten, as they won’t be there anymore. If you choose to germinate outdoors, you should protect your seeds from animals and the worst of the weather.
16. Too much light
Cannabis seeds don’t require any light to germinate. If they are exposed to excessive UV light, then they might struggle to germinate. Therefore, however you choose to germinate your seeds, you should do so out of strong, direct light.
Do cannabis seeds germinate better in the dark?
While cannabis seeds have developed to germinate in total darkness, it’s not essential. Mostly, they are totally indifferent to light—until the first cotyledons appear. The main thing is to keep them out of strong light, such as sunlight or grow lights. But a little light exposure shouldn’t affect germination.
Germinating cannabis seeds: Practice makes perfect
Germinating cannabis seeds is mostly a matter of balancing a variety of environmental factors. None of the requirements to germinate are difficult to achieve, but seeds can be fiddly, and will reward those who take the care to give them the correct environment.
That being said, you can also find cannabis seeds erupting from the ground under the most inhospitable situations, which can go on to develop into large and productive plants. Still, in most cases, cannabis seeds prefer a stable and suitable environment.