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Germinating Cannabis seeds: FAQ
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In this blog item Can you germinate cannabis seeds in a glass of water? What is the best temperature for germinating cannabis seeds? Germinating cannabis seeds in the dark? Or in light? Can I use potting soil, soil or rock wool? Jiffy/peat pallet to germinate seeds?Germinating cannabis seeds on cotton wool / kitchen paper / coffee filter? When can I let cannabis seeds germinate?Can I use a propagator? After germinating?Best way to germinate cannabis seeds?  How long does it take for cannabis seeds to germinate? What can be wrong when cannabis seeds don’t germinate? Do your seedlings look very weak?The seedling has snapped in two?

Germinating Cannabis seeds: FAQ

You can germinate your cannabis seeds in different ways. Of course you want to cultivate beautiful, healthy plants. This is possible by using the right method. We have listed the most frequently asked questions about the germination of cannabis seeds.

Do you have problems germinating? We have also written out the most common causes of non-germination for you, with suitable solutions! Hereby we provide you answers tot he most frequently asked questions about germinating cannabis seeds, plus the most common mistakes made by new growers. Do you have problems germinating, but is your question not listed? Please contact us: our specialists will be happy to help you. 

spongepot tray spongepot pot

Order the Spongepot germination kit for only €5,95! Succes guaranteed!

Can you germinate cannabis seeds in a glass of water? 

A method that is often recommended is to germinate the cannabis seeds in a glass of water. This works as follows; fill a glass with pure water and drop the seeds into it. Place the glass in a dark environement and wait until you see the root appear. Usually this happens after two to three days. After sprouting you can plant the seeds in the growing medium. 

However, there are also risks associated with germinating cannabis seeds in a glass of water: there is a good chance that the seeds will suffocate or start rotting. You also run the risk that the sprouted seeds will be damaged when moving from glass to soil.

What is the best temperature for germinating cannabis seeds? 

For most types of cannabis, the best temperature for germination of seeds is 20-22°C. Tropical sativas like it a bit warmer, a kush from the mountains prefers to be a bit cooler. 

Germinating cannabis seeds in the dark? Or in light? 

Weed seeds do not need any light at all to germinate: they can do this perfectly in the dark. Until the first leaves have appeared, it doesn't make much sense to place them under a lamp. If you have trouble keeping your grow space warm enough, a grow light often helps to raise the daytime temperature just a few degrees to improve germination. 

Can I use potting soil, soil or rock wool? 

A good way to germinate cannabis seeds is to sow them directly into your growing medium. This can be potting soil/earth, coconut or rock wool. Choose organic potting soil without added fertilizer, potting soil intended for sowing, unfertilized coconut or rock wool. Make a hole of ±0.5 cm deep for each seed and cover them after you have placed them in the hole. Spray lightly aftewards so they stay moist.

Make sure that the medium does not dry out, but also does not become very saturated with water. The ideal humidity (from now until flowering) is between 50-70%. After 3-7 days you should see the seedlings appear.

Jiffy/peat pallet to germinate seeds?

Although every garden centre will highly recommend these, jiffy's and peat pellets are not very suitable for germinating cannabis seeds. They often have the wrong acidity, which complicates the process. Also, when you’re not on time with transplanting they will start to cause problems with root rot because they retain too much water.

Germinating cannabis seeds on cotton wool / kitchen paper / coffee filter? 

Another method for germinating seeds is to place them in damp cotton wool until the root appears. Moisten a handful of cotton wool and place the seeds in the middle. Put them in a box or hang them in a bag until the root appears. This method has a number of major disadvantages, the main ones being the increased risk of mould or rot and the risk of damage to the root when transplanting.

A better alternative is using an old-fashioned paper coffee filters.
Place the seeds between the layers of the filter and moisten it. Do not make it too wet! Place the filter in a zip bag. Gravity will help with germination, so hang the bag on this inside of a kitchen cupboard. With this method, seeds germinate within 24-48 hours.

When they have germinated, you can plant them very carefully in a hole of ±1cm deep in your medium. 

When can I let cannabis seeds germinate?

Technically you can germinate seeds all year round. Depending on what type of cannabis seed you have and whether you grow indoors or outdoors, certain periods are better suited than others.

Indoors: All year round

Outside: Feminized and regular seeds are best germinated soon, in the northern hemisphere this means that you start germinating about mid-April, so they can go outside after the Ice Saints, mid-May. If you start later, your plants may not be fully grown when they start flowering. Sowing plants in autumn for outdoors is pointless. Because of the short day length, they start to flower immediately and will never grow into a beautiful shrub with a large harvest.

The advantage of Autoflowers is that they grow much faster compared to their ‘normal’ sisters. They don’t like to be transplanted eithers. You can best germinate them when it’s warm enough at night to leave the seedlings outside. The best time is from mid-may.

Can I use a propagator? 

A propagator is a very handy tool for helping your seeds with germination. They keep the humidity high and you can heat them with a heat mat. Make sure that there is sufficient ventilation/airflow to prevent high humidity and mould formation/rot.

After germinating?

After your cannabis seeds have germinated, carefully pot them in the growing medium. Make a hole of about one cm deep and place the seedling, then cover it and spray lightly. It’s very important to not that seeds contain all the energy they need to grow fort he first two weeks. You don’t need to use any fertilizer, this can even harm them by giving way too much nutrients which can cause them to burn.

Best way to germinate cannabis seeds?  

Directly in your medium or in the Spongepot is for most people the best way. This way you have the least chance of damaging the delicate roots and your plants can start growing right away. 

Spongepot is a perfect medium for most people. You have the least chance of damaging the delicate roots and your plants start growing right away.
However, many growers swear by the coffee filter method or the glass of water. The advantage is that you’ll know very accurately when they will start germinating. Do what works best for you and what you feel comfortable with.

How long does it take for cannabis seeds to germinate? 

This depends greatly on the type and temperature. In general seeds start germinating after 24 hours up to 4 days. For some species it can take up to 10 days.
If your seeds are still not germinated after that, this will probably not happen.

What can be wrong when cannabis seeds don’t germinate? 

It is not always your fault if the seeds do not germinate. There are many reasons that cause difficult germination.

  • The soil can be contaminated with fungi, or the garden centre has recommended the wrong soil.
  • Sweaty hands can contain acids, and this can cause delay.
  • Also, fungi on the seeds or soil can be transmitted by the hands.
  • Hard water? Earth that is too wet or too dry? Too cold? Too hot? These factors can all cause poor germination of your cannabis seeds.
  • It is possible that poor germination is caused by an incorrectly calibrated or defective EC meter. 

Possible problems:

Fungal infection

One of the most common causes of poor or completely failed germination is a fungal infection. This can be recognized by a white, fluffy looking substance on one side of the seed. Mould can be caused by several factors, for example an environment that is too cold and wet or an environment without oxygen. Also, the soil can be of inferior quality, an incorrect acidity can cause mould, as well as factors such as high humidity, poor air circulation, wrong temperatures and over-watering.

If the inside of the cannabis seed has changed into a yellowish substance you’ll know that it has been affected by mould.

TIP: If you use a small greenhouse you need to stimulate the air circulation extra. Both seeds and the ultra young seedlings benefit from good air circulation. The growing medium should also be well aerated. In addition, the humidity should be 50%-80%. If you cover your seeds, make sure you leave the lid half open so that there is sufficient air circulation. This will also keep the humidity at the right level.

Too high or too low temperature

Did your cannabis seed start well and developed a root, but then stopped growing completely? Mildew can be a cause, but also take a look at the temperature. Both too high and too low temperatures can cause the cannabis seed to stop germinating / growing. 

The EC value, or salt value, is too high

If an emerging seedling suddenly dies, the salt value can be a possible cause. Make sure you check the value of the substrate. 
Don’t forget to check you EC meter. It’s possible that it’s deffect or you might need to re-calibrate it.

The quality of the water

The correct PH value of the water is important. This should be as follows:

  • Germinating cannabis seeds in soil: PH value 6.5
  • Germinating cannabis seeds in rock wool: PH value 5.6 - 5.8

Tap water contains salts, chlorine and fluoride, which is the main reason for seeds not to start germinating. For this reason it’s best to use clean, bottled water.
These substances can hinder the growth of the very sensitive seedling. If you’re still going to use tap water, make sure you take hot water and let it cool down outside in a bucket. This will at least allow the chlorine to evaporate.

Very important: You do not have to give nutrients to cannabis seeds and seedlings. Nutrients do more harm than good in the very beginning. 

Do not use peat pellets and jiffys. Advertisements will claim that it is good for germinating your cannabis seeds, but this is not true at all. The PH value of these products is too high, which inhibits germination. 

Do your seedlings look very weak?

When your seedlings look very fragile and weak, it is most likely caused by too little light. Make sure that young plants get more light, for example by moving the light source or bringing the plants closer to the light source. 

TIP: Has your seedling become too long and stretched? Place a stick next to it to support the plant until it has been strengthened, and place the plant closer to the light source. 

The seedling has snapped in two?

A broken seedling is usually caused by a fungus that has weakened the stem. This causes the plant to wilt and die.

TIP: The right amount of water is important: too little water causes the plants to dry out. Too much water can cause the seedlings to drown and it can cause mould. In short: the substrate should always be moist, but not too much.


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