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Cannabis Seedlings Yellowing: Causes, Solutions & Prevention

June 22, 2023

Seeing your cannabis seedlings yellowing may cause concern, but it’s not a severe issue if you take prompt remedial action. The discoloration is typically a sign that the growing conditions aren’t optimal. There may be a primary reason or a combination of contributing factors.

Although the problem could harm your seedlings if left unattended, it’s preventable and treatable. Knowing why leaves turn yellow and identifying the symptoms is vital to providing solutions before the situation worsens. 

Let’s dive into this topic below.

Cannabis seedlings yellowing: 7 causes and solutions

The main challenge for cultivators, especially beginners, is diagnosing the specific cause of a plant problem during the marijuana life cycle. Yellowing seedlings are among these tricky issues, as there are several possible reasons.

Cotyledon leaves turning yellow is a natural phenomenon and not a sign of an unhealthy crop. These leaves are designed to start the growth process until your plant produces more foliage, then they discolor before falling off.

It’s when you notice larger leaves yellowing that you need to consider the following factors to be able to take remedial action. 

overwatering cannabis seedlings


If you see the first set of true leaves turning yellow and other signs of foliage discoloring, consider overwatered seedlings as the cause.

Overwatering is a common issue if you sow a small seedling in a big pot. If the roots are moist for long periods, the leaves may turn yellow. As the change in hue is also a symptom of several other plant issues, clear signs of damping off in seedlings include drooping.

When using a big container, don’t completely soak the substrate to avoid your cannabis seedling yellowing due to overhydration. Add liquid around the plant until the leaves develop before watering thoroughly.

Knowing how to water seedlings in a big pot to ensure your plants get enough moisture is critical. Check if the medium is dry before adding more. For soil, insert your finger, and if it feels dry up to your first knuckle, water it. A light container is also an indication that it’s time to hydrate your crop.

One of the best watering practices for seedlings grown in coco coir is to do it every 1–2 days. If the top inch feels wet, pause until it gets dry. 

Thick and muddy soil

Another possible reason for weed seedlings turning yellow is thick and muddy soil, which causes water-saturation. The roots are oxygen-deprived, stunting growth and causing the leaves to discolor. 

The problem is magnified if you overwater your plants during the seedling stage in weed. An excellent type of soil is loam, as it’s a mixture of sand, silt, and clay, each offering their best qualities.

Lack of light

It’s vital to provide sufficient light for weed seedlings to photosynthesize. This process converts light, water, and oxygen into the energy they require to develop. Without producing carbohydrates, their reserves deplete, resulting in cannabis seedlings turning yellow before they die.

Besides discoloring, you also get stretchy weed seedlings when the stems reach toward a light source. The space between leaf nodes also lengthens. If your plants don’t get enough illumination during the flowering stage, they may be unable to produce buds.

Light burn

While sufficient illumination is essential for photosynthesis, avoid over-exposure that can lead to light burn. Placing plants too close to the grow lamps may cause the leaves closest to them to turn yellow or brown. Keeping your crops at a safe distance reduces the risk.

Before you notice your cannabis seedlings yellowing, you may see their leaves pointing upwards. Sometimes, there aren’t any pre-discoloration symptoms.

Yellow leaves may also be due to a nitrogen deficiency. The difference is the foliage drops off on its own, while those resulting from light burn are difficult to pluck. With too much illumination, the leaves’ inner veins remain green while the tips change color.

Cannabis light burn

Heat stress

Another possible reason why weed leaves turn yellow is heat stress. Weed plants can tolerate light and warmth to a certain extent, but after a point, they display signs of the problem.

Symptoms of heat stress include seedlings sprouting yellow or brown leaves, especially those close to the light source. Some foliage may appear burned in places where the effect is more intense. 

When there’s too much heat, the leaves’ edges curl up and fold like a cup or taco before discoloration occurs.

This phenomenon also occurs with outdoor plants if they don’t get enough water when the weather is hot and dry. Crops experience heat stress in low humidity conditions, too. Some solutions include adding mulch, watering, and keeping your plants in the shade.

Lack of nutrients

Cannabis seedlings yellowing may result from a nutrient deficiency. If you adequately feed your plant, the problem might be caused by incorrect pH levels. The issue is unlikely to occur in soil, as the substrate contains sufficient food for your crops in the first few weeks.

If growing in non-soil media, it’s vital to provide your seedlings specific nutrients for hydro or coco from germination. They can’t thrive on the energy in the seed alone.

Transplant shock

Transplant shock is a growth setback plants experience when transferred from one environment to another. It also refers to the stress seedlings go through if their roots are damaged during the process. 

Your plant activates its survival mechanisms by shutting down and conserving energy. You notice weed seedlings turning yellow and leaves wilting, curling, and dying. This behavior is normal, and most crops recover. Seeing the development of young foliage in the middle is a good sign.

Prune severely damaged leaves when you find new growth to enable your crop to focus its energy on further development.

When transplanting a seedling, allow it to adapt to its new environment by gradually increasing the time it spends there

Transplanting Autoflowers

Say goodbye to yellow cannabis seedlings

Knowing the signs and ways to prevent and treat a cannabis seedling yellowing problem helps make it less of a threat

Using top-quality cannabis seeds ensures a high germination success rate and healthier seedlings, minimizing the risk of potential problems. Browse our store to find a range of premium cannabis seeds across autoflowering, regular, and feminized strains.


We’ve compiled answers to some of the most commonly asked questions on how to solve seedling problems below.

What color are healthy cannabis seedlings?

Under optimal growing conditions, healthy marijuana seedlings are short, and their dense leaves have a vibrant green hue.

Can yellow cannabis seedlings recover?

You can recover from weed seedling leaves turning yellow if you identify the cause of the problem and promptly treat your plant. Raise your grow lights when diagnosing the issue. Avoid stress to help your crop recover quicker.

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