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How To Master The Cannabis Seedling Stage

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The Cannabis seedling stage – Growing marijuana can be a very complicated process, especially if you do not know your way around the intricate processes. In order to achieve a healthy bumper harvest, you need to get it right straight from the beginning.

From buying the right seeds, using the right medium and, keeping the right environment, we have got you covered. Join us on this detailed guide and by the end of it, you will be a master at all things cannabis seedlings. 

Pick the right genetics, containers, and medium for your seedlings

You have to start right, to finish right.

Ensure you source very high quality seeds that have characteristics you are looking for in terms of method of growing (indoor or outdoor), skill, grow equipment, strain preferences (taste and effect) and other such factors.

In terms of medium, light soil that is well-aerated and slightly acidic with a 6.3-6.5 ph is ideal. Adding 20-50% perlite to the soil aids aeration as well as nutrient retention. The more nutrients you plan on giving, the more perlite you should include as it helps in drainage and prevents nutrient lockout.

When watering, only do so when the soil has completely dried out and only around the stem. Also, remember that seedlings, especially autoflowering ones, are very sensitive to nutrients. They should never be planted in hot soil (nutrient dense soil). In fact, generally, wait until they grow 3-4 sets of true leaves before you start feeding them. 

We will also give you a few tips on the pots you should use:

Autoflowering cannabis seeds: Plant directly into the final pots as they have a short life cycle that does not allow for the stresses involved in movement. For most autoflower strains, consider strain but on average, 5-15l pots will do.

Feminized cannabis seeds: You can start with “Easy start germination pots” and transplant once they outgrow their starter pots. Usually this is after they grow sets of true leaves which spread to cover the whole container’s circumference.

Most growers would then move them to 12L pots. While choosing a pot, consider the strain and also the option of up-potting severally to maximize your plants development. What this means is that you don’t have to immediately transplant seedlings to a huge pot.

Other factors to consider when picking a pot:

  • Ensure your pots have adequate drainage holes to guard against root rot and fungal pathogens (you can make holes yourself).
  • Use smart pots that maximize aeration if you can. 
  • Use the right size of pot. A too large pot might lead to over watering as the plant will not be able to adequately drain the water, which could lead to root drowning, and pathogens and pests.

Picking the right germination techniques

For successful cannabis seed germination, four things are vital: moisture, warmth, time and darkness. The following techniques are likely to give you good germinating results: 

  • Paper towel method

Cannabis seeds are kept between some moist papers which are then placed into a plastic container that has a lid. The container is then kept in a dark, warm place with the lid cracked slightly open. Ideal temperatures are between 20–25°C

  • Glass of water method

In this method of germination, seeds are simply dropped into a glass of water placed in a cupboard that is at 20–25°C. Within 24-4 hours, they should have sprouted and should be ready to plant. Please note to transfer them to the paper towel method if they don’t germinate within 48 hours as leaving them in water for longer than that will rot them. 

  • Use a  Starter Kits

Several starter kit are available in the market which have everything you need. You can follow the steps and get the ball rolling.

Mastering the seedling stage

This is where the real challenge begins. Cannabis seedlings tend to be extremely fragile with their frail roots and tiny set of cotyledons. Minor stressors can destroy your seedlings in a matter of hours. Understanding your seedlings allows you to manage this stage like an expert and grow strong, healthy plants.  

Optimal temperature, humidity, and light for cannabis seedlings

Cannabis seedlings have very specific needs as far as humidity, temperature, and lighting are concerned and missing the mark could lead to detrimental results. To this end and where possible, grow your seedlings in a propagator to create the perfect environment for your cannabis seedlings to flourish. The ideal environment for cannabis seedlings to flourish are:

  • Temperature

Daytime temperatures should be kept at 20–25°C while nighttime temperatures should be roughly 4–5°C cooler. High temperatures stress the seedlings and stunt their growth, they could even be fatal at an early stage. You can tell your seedlings are undergoing heat stress if the leaves start drying up and curling up at the edges or wilting with downward folding tips. Their foliage could also turn pale and they could develop purple or red stems. 

Conversely, too cold temperatures can freeze the cells of a seedling affecting its ability to transport and utilize water, nutrients, and oxygen. If not handled in time, it could lead to stunted growth, and eventual death. Slow growth, wilting foliage and poor plant turgor indicate too low temperatures. 

  • Humidity

Early on when the roots are still developing and you, the seedling gets most of its water via osmosis using its leaves. For optimization of this process, relative humidity of 40–60% should be maintained. 

If the humidity is below 20% , the growth of the seedlings could be  seriously stunted and they may develop symptoms that are similar to nutrient deficient ones such as spotted or yellow leaves. On the other hand, if humidity levels are above 60%, the plants could develop wet spots which can cause wilting or rotting of the foliage, and attract fungi as well as other pathogens. 

Once the seedlings get to the vegetative phase, relative humidity can be maintained at 50%.

  • Lights

Cannabis seedlings are very sensitive to light, and tend to burn under strong LED or HID bulbs. Light stress makes them develop burnt, crinkled leaves the same way as in adult plants. If the seedlings don’t get enough light, they tend to grow tall and lanky and might end up toppling over.   

Growing your seedlings under “an 18/6 light cycle using CFL bulbs with a blue light spectrum for the first 10–14 days” is bound to produce good results. You can then move them to stronger LED or HID lights after they develop healthy true leaves for their vegetating phase. . 

Growing seedlings outdoors

Obviously, outdoor growers do not have the liberty to control the environment of their seedlings at the push of a button. However, they can:

  1. Keep the seedlings indoors, and under CFL lights to keep them safe from the elements the first two weeks.
  2. Keep the seedlings outdoors  in the day and move them indoors at night to protect them from elements like rain and cold, as long as outside temperatures are consistently between 20–25°C .
  3. Keep your seedlings permanently outdoors in a greenhouse, propagator, or polytunnel where you can control temperature and humidity. 

What exactly happens during the seedling stage?

Cannabis seeds house inside their dark, hard shells all the genetic information needed to sprout, and grow big, luscious plants. When exposed to warmth and humidity, the seeds absorb water from the environment in a process called imbibition which activates special enzymes that trigger germination. 

With germination, a small white root appears known as the taproot which burrows itself underground looking for water as well as a shoot that goes up in search of light. , 

Cannabis seeds contain two cotyledons (embryonic leaves) which unravel pushing the casing of the seed from the shoot. After the emergence of the cotyledons, the first set of true leaves develop, which growing out of the dominant stem will have only one finger. 

Rapid growth, as well as vibrant green foliage, signifies healthy seedlings.

Watering your seedlings

Take care to give your seedlings just enough water and ensure the pots can drain out properly.

  • Overwatering: A crime committed by many a rookie grower afraid of letting the soil dry out, this leads to drowning the roots and exposing them to rot, fungi, and other pests while also causing the seedling to be starved of oxygen. Planting your seedlings in a pot that is too big will lead to the excess soil holding water that the plant cannot access. In the same breath, having a pot that is too small leads to the soil drying out too fast, requiring too regular watering which could also lead to overwatering.
  • Underwatering

While it is not quite as common as overwatering, this could happen especially to new growers who have received a warning to avoid overwatering their plants. 

Cannabis plants are constantly losing moisture in a process called transpiration (evaporation through the leaves). This plays a vital role in aiding the plant transport water through its stem from its roots. When transpiration keeps taking place and the roots can’t find water, vital functions of the plant could slow down, which could lead to irreversible effects, especially if the root system was under developed. 

Unfortunately, under watering symptoms are similar to overwatering ones, which are wilting and drooping. However, if your soil is bone dry, that is probably a good indicator!

How to prevent damping off

“Damping off” is the phenomenon by which on a paltry 24 hours, you could lose all your seedlings. It is caused by fungus such as Botrytis, Pythium and Fusarium. This fungus thrives in damp, humid areas and will totally destroy your crop and is mostly irreversible.

You can take the following measures to avoid damping off:

  • Keep close tabs on your grow space’s relative humidity and temperature.
  • Avoid overwatering your plants and ensure your pots drain well.
  • Before you use soil, sterilize it by baking it at a temperature of 85°C .
  • Remove any affected seedlings immediately to avoid spread of the fungi and thoroughly sterilize the area. 

Other factors to look out for in your young seedlings:

Nutrient burn: Fragile cannabis seedlings easily burn in nutrient-rich soil as they are self-sufficient in that area. After 3-4 weeks is a good time to start feeding the seedlings or at least after they have developed 4-5 true leaf sets or three nodes.

Transplanting shock: Transplanting is a stressful process. Feeding your plants too soon after this could lead to nutrient lockout. Give your seedlings about 3-7 days to adjust and start off with a mild nutrient combination such as an NPK ratio of 4:2:3.

Stretchy seedlings: Growing seedlings in inadequate light as well as keeping them in the dark 24 hours after germination could lead to them developing unnaturally long and flimsy stalks. This is because the lack of light will make them stretch abnormally. Avoid this by placing them appx. 5cms under blue spectrum cfls. 

Go organic as much as possible. Try building vibrant soil right from the get-go. Organic cannabis plants have higher yields of far better quality.

Look out for pests including: Fungus gnats, spider mites, leaf miners and mold such as White powdery mildew, Pythium, and Fusarium.

Cannabis seedlings thrive in humid, warm conditions. Unfortunately, so do pests and diseases. Growing your seeds in a propagator and keeping things extra clean can go away in ensuring your seedlings stay healthy. 

When exactly should you transplant your seedlings?

Unfortunately, this is not an exact science. Careful looking out for the cues is a better approach to handling this correctly. Seeds should be transplanted at the first sighting of the taproot, that is, when it is about 1-2 cm, while seedlings should ideally be transplanted when they have fully covered the circumference of their container, taking care to transplant the seedling and all its soil. 

Always remember to very gently handle your seedlings as even minute damage to its roots could be detrimental. 


Though it is quite an intricate process, mastering the cannabis seedling stage is quite doable. You now have all the skills you require so go on and get your hands dirty! With this fantastic start, you are bound to experience bumper harvests of quality, delicious bud. 

Sebastian is a passionate advocate of CBD's therapeutic potential, dedicating himself to exploring its diverse benefits. As a seasoned writer, he eloquently shares his insights and personal experiences with CBD, aiming to educate readers about its transformative power. His life's mission is promoting holistic wellness, with CBD at the heart of his advocacy.

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