Growing cannabis begins with a small seedling that is meant to develop into a vigorous plant. However, this early stage presents many challenges. From light and temperature to proper watering and potential problems like yellow leaves or stunted growth – here's what you need to look out for to ensure your cannabis seedling grows healthy.

What is a cannabis seedling?

A cannabis seedling is the first growth phase of the plant after germination. During this stage, the plant is particularly sensitive and needs optimal conditions to develop well. These include:

  • A loose, well-aerated substrate
  • Sufficient, but not too much light
  • Stable temperatures between 20–26 °C
  • Regular, careful watering

Typical problems with cannabis seedlings

Sometimes a cannabis seedling suddenly stops growing – this can have various causes:

  • Too much or too little water: Waterlogging or drought inhibits growth.
  • Nutrient stress: Too much fertilizer overwhelms young plants – less is more here.
  • Temperature fluctuations: Below 18 °C or above 30 °C is critical.
  • Poor air circulation: Can lead to mold or stagnant growth.

Cuttings are less likely to have this problem – but with seedlings, every little thing counts.

How much light does a cannabis seedling need?

For the first few days, soft LED lighting with approximately 6500K is sufficient. An 18/6 cycle is ideal: 18 hours of light, 6 hours of darkness. The distance from the lamp is also important—approximately 30–50 cm, depending on the intensity.

Yellow leaves on cannabis seedlings: What to do?

If your seedling gets yellow leaves, it could be a sign of:

  • Overwatering (→ roots rot)
  • Nutrient deficiency (often nitrogen)
  • Too much light or heat

It usually helps to rethink your watering habits or to add a mild fertilizer .

When and how should you repot?

Repotting is worthwhile as soon as the roots peek out from the bottom of the pot or the seedling has 3–4 pairs of leaves. Here's how to do it correctly:

  • Carefully remove from the pot
  • Plant in fresh soil with good drainage
  • Water lightly and protect from direct light for 2–3 days

Why is my seedling “asparagusing”?

A "sprouting" seedling grows too quickly and becomes unstable. The cause is usually too little light. Remedy:

  • Bring the lamp closer to the plant
  • Use a fan for light airflow
  • When repotting, place the plant deeper into the soil

Conclusion: Growing cannabis seedlings successfully

The seedling phase is crucial for the future success of your plants. With the right amount of light, water, warmth, and attention, your seedling will soon become a strong plant. Still looking for suitable seeds or grow equipment ? Then visit our shop.

FAQs

How much light does a cannabis seedling need?
A seedling needs about 18 hours of light per day – LEDs with a color temperature of 6500K are ideal.
Why are my cannabis seedling leaves turning yellow?
Often, it's due to too much water or a lack of nitrogen. Too much light can also cause stress.
What to do if the seedling stops growing?
Check light, water, temperature, and air circulation. It usually helps to water less and maintain a stable environment.
When should you repot a cannabis seedling?
As soon as the roots appear at the bottom of the pot or the seedling has 3-4 pairs of leaves.
What does it mean when the seedling “asparaguses”?
The seedling grows too quickly, usually due to insufficient light. Remedy: Move the lamp closer and stabilize the plant.