After seed germination, the Cannabis plant enters the seedling stage. In this article, you’ll find information about how to take care of your seedling, some problems that may arise and how to take care of them.

Cannabis seedlings like relatively moist conditions. Temperatures should remain warm and lights should be placed near them and moved up as the plants grow. Finally, a Cannabis seedling needs little amounts of nutrients and their needs will grow as the plant gets bigger and stronger.

Seedling stage (2 to 3 weeks)

When the Marijuana seed opens, the first pair of small round leaves that appear are called “cotyledons”. After that, the little Cannabis plant starts producing serrated leaves, not the characteristic digitate leaves, only single serrated leaflets. As the plant grows, new leaves with more leaflets start to develop until the plant produces digitate leaves with serrated borders we can all identify as Cannabis fan leaves. When these leaves appear, the plant enters into the vegetative stage. This process may take up to three weeks.

Factors that lead to healthy growth of Cannabis seedlings

  • Warm temperature: Seedlings are very sensitive to temperature, they thrive with temperatures around 72 – 79 F (22 – 26º C).
  • Relatively low light intensity: Young plants are not yet able to process high-intensity light. Led lights or low wattage lights are better for this stage. A cold (blue) spectrum light is better for this stage, as they promote vegetative growth.
  • Adequate light distance: Keep in mind the distance between the plant and the grow lights, which depends on their intensity and temperature. Start with a distance of about 4 inches (10 cm) if you are growing with low-intensity lights and do the “hand test”, placing your hands on the top of your plants for 30 seconds. If it feels like too much heat for your hand, it’s probably too much for the plant too, so move up your lamp until it feels warm but not hot. When growing outdoors, just try to place your plants where the sunlight reaches them and keep an eye on them so the soil never gets to dry up.
  • Light/Photoperiod: Start with 18 hours of light and 6 hours of darkness.
  • Nutrition: Seedlings need a low dosage of nutrients or they may experience nutrient burn. If you are growing on soil, choose light mixes and avoid extra fertilization in the first week or two. After that, you can start your fertilizing plan.
  • Pot size: Once germinated, place your seed/seedling in a small pot or cup with drainage for better results. Then move your seedling to a bigger pot once it has grown a few cms or if you see the roots coming out through the drainage holes. 
  • Watering: Water your seedlings with a sprayer to avoid overwatering. Use clean water only.
  • Relative humidity: A very dry environment may cause your seedling to dry up easily. Keep it around 65 – 80%.
  • pH levels: Keep pH levels between 6.5 and 7 for your seedling to be able to absorb all the nutrients present in the substrate.

Always keep an eye on these factors, if they are not taken care of, your plant may experience stunted growth and finally die. Let’s see the typical problems a seedling may have.

Factors that lead to stunted growth of Cannabis seedlings

Your marijuana seedling is not growing? There are many factors that may lead to stunted growth in the seedling stage, let’s take a look at some of them.

Problems with watering and pot size

Underwatering and overwatering may cause stunted growth. Small seedlings growing in big pots may experience overwatering problems, as roots need oxygen to develop and their roots systems are yet incapable of drinking that much water. In this case, the seedling seems droopy and weak, because they are slowly drowning. If this is the case, just add less water and only around the seedling, let the plant absorb some of it before watering again.

On the contrary, if the pot is too small for the seedling, growth would be stunted as well. The roots need space to develop and your risks of having problems with watering are high. In this case, just transplant it to a bigger pot to avoid “root bound”. Poor drainage also leads to these problems.

Problems with nutrients

Nutrients toxicity usually happens when the growing medium has too many nutrients for the stage and the plants are not able to absorb them. You’ll notice burnt tips and a dark green color in the leaves if this is the case.

Nutrient deficiency may happen either because of the growing medium not having any of them or because it has too much of them, so pH levels are off and those nutrients are not available for the plant to uptake, despite being present in the mix. The most common at this stage is Nitrogen deficiency, which shows with older leaves turning yellow and then brown and crispy.

Sometimes, this happens also when the plant is in a very small pot and has already used all the nutrients in the soil. If this is the case, the best idea is to transplant it into a bigger pot containing a soil mix and apply nutrients for the vegetative stage. Remember to monitor watering schedules for better results.

Problems with temperature

If temperatures are too high or too low, seedlings are bound to experience stunted growth. This shows with leaves tips turning up and curling. If this is the case, lower the environment temperature and monitor for changes. As stated before, keep the environment temperatures between 72 – 79 F (22 – 26º C).

Problems with light

Too much light or not enough light also leads to stunted growth.

If your seedlings are not receiving enough light, they’ll grow very tall and weak, with few leaves. You’ll see the stem growing tall and white.  If this is the case, your growing light needs to be closer to the plant. Always do the “hand test”, placing your hands on the top of your plants for 30 seconds. So, if it feels like too much heat for your hand, it’s probably too much for the plant too, so move up your lamp until it feels warm but not hot.

When they are receiving too much light, leaves are curled and seem burnt. If this is the case, move your lights up and also do the “hand test”.

cannabis seedling with stretched stem
Cannabis seedling with stretched stem
PH: Chanvre QuebecFe

Take care of your Cannabis seedlings!

At the seedling stage, Cannabis plants are very sensitive and vulnerable, their root system is not yet developed and they need special care, little watering, and humidity. A healthy seedling has a short stem and green leaves.

Remember to take notes about this stage and monitor your environmental factors. You can do this with our free app Grow with Jane! Follow this link to download it today. Get the app.

Hopefully, your seedling will rapidly grow and enter the next stage a healthy plant. As said before, when the digitate leaves with serrated borders we can all identify as Cannabis fan leaves appear, the plant enters into the vegetative stage.

Full article: What happens in the vegetative stage of a Cannabis plant

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