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germinate weed seeds in dark or light

Generally speaking, seeds require a dark environment in order to germinate. After all, in nature cannabis seeds find their home in the dark embrace of soil. It can be hard to determine exactly how much light is too much for your seeds; however, err on the side of caution and germinate out of direct light. There’s no need to use your grow lights until after germination has occurred.

Once they pop, seedlings are very delicate and must be watered carefully. When germinating, your medium should be damp, but not overly wet for best results. On the other hand, a dry environment is basically a death sentence for your seeds. They need a constant source of moisture to sprout, otherwise they’re good as duds.


Many people choose to germinate their seeds using paper towels. However, others choose to do so directly in soil. Of course, germinating your seeds in soil isn’t inherently bad, but it can come with its own set of challenges, and is generally not recommended unless necessary.

The amount of water you supply your seeds during the germination process will also affect their ability to successfully germinate. Some growers attempt to germinate by “drowning” them in a glass of water. While this ensures they will not go thirsty, it can actually be more harmful than helpful.

Seeds that have been improperly stored may also fail to germinate. These tiny packages of DNA prefer to be kept in a cool, dark place with moderate humidity. Exposing them to heat, light, or extreme humidity levels (both high and low) could result in seeds losing their viability. As long as you source your seeds from reputable seedbanks and store them appropriately, you shouldn’t have to worry about bad seeds ruining your chances of successful germination.

Plant the seeds about 1 to 2 cm deep, so that it does not require too much energy for the stem and first leaves to pop up through the soil.

To use the pellets, simply soak them in water for around ten minutes. They will expand.

Put your seeds on one half of the paper towel and fold the other half over them, so that they are covered. Then take the second plate and put it upside down on the bottom one, forming a dark cavern between the two plates for the seed to germinate.

Best LED Grow Lights For Starting Seeds

To store your seeds for the best results, keep them in a cool, dark place. A basement works well, as does a refrigerator.

Once your seedlings have been moved and they have developed 5-7 true leaves this is a good indication they are happy and beginning the veg phase. You can maintain 18/6 or move up to 20/4 on lighting schedules some recommend 24hr but again IME plants still need a few hours of darkness to recover.
At this point you can maintain the blue light at around 46-52cm height and begin feeding with nutrients. I recommend Canna Bio and make sure the first few times use a diluted solution just to allow the plants a chance to adapt to their new diet. After a week you can switch to full strength feed and growth will explode dramatically.
For Autos they will flower when ready or mature enough hense the “Auto” then you can switch to red or a combination of red and blue light all the way through until harvest.
Photo’s will stay in veg under blue light as long as you keep them there and will just keep bushing out until you switch to red or combination light telling the plant that flowering will begin.
During flowering light height will depend on the strain you are growing and light you are using x square metre grow space but during flowering roughly 36 – 40cm from canopy is a good benchmark. With LED units you can go a little closer as heat is not as much of an issue but make sure your whole plant is getting equal amounts of light.

Once the cotyledon (first round leaves) emerge they occasionally have the seed casing attached make sure you allow it to fall of naturally don’t pull it off.
At this stage you can drop your blue light down to 46 – 60 cm from the cotyledon depending on the light you are using. Maintain this and only water to retain moisture allowing top inch of substrate to dry before watering again until you have a couple of sets of true leaves.
At this stage you plant will be strong enough to survive transplant into larger pots.
If you are using Autoflowers plant the propagation plug in their final pot, depending on the strain grow space this will vary between 10L – 15L pots, I personally recommend Airpots if you’re after very healthy plants. (healthy plants yield bigger)
If you are using photoperiod this will also be different depending on strain, grow space and how long you veg for, they can be transplanted into gradually larger pots ending up in anything up to 20L.

Cannabis seeds need no light when they are germinating. In fact, they require an absence of light. All of the methods below call for darkness.

For example, if your pulse sequence was [R, FR, R, FR, R], it would be equivalent to [R] since R was the last pulse in the sequence and all the seeds would germinate.

Light helps lettuce seeds germinate, so why would it inhibit cannabis germination?

Why is darkness recommended for germination? Doesnt seem to make much sense to me, why would darkness be beneficial to the seed in any way? Just curious. I have some seedlings already but decided to go for a few more plants, so i’ve put the seeds in the pots in the same room, threw some black garbage bags over the pots to avoid some of the light + it add more moisture..

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Well my argument was that it seems unnecessary and possibly harmful to go through the paper method, putting it in a cup, transplating (some seems to transplant 2-3 times – very stressful to the plant to say the least). That’s a a real hassle when handling a lof of plants.

You do not need lights to germinate cannabis seeds and if you do then it is not at all going to help speed up the process; I mean, how are lights going to help your seed absorb more moisture and root?

With pot, light seems to contribute little to germination success however.

catofcuriosity: I’ve heard that too, but a lot of times i’ve germinated seeds in clear plastic cups, the roots has been exposed to my 1200w HPS lights, no problem at all.. The pots i’m using now are of the usual kind (black) and the roots are not exposed to light, but yes it’s possible that light maybe seeks its way through the soil and therefore it could be harmful to the roots..