Our best 10-OH strains Toda
Yellow leaves on cannabis plants? Don’t worry—this happens even to the most experienced growers. When the rich green slowly turns pale yellow, your plant is sending out a warning. Something’s wrong, and now it’s up to you to find the cause and take action.
Whether it’s due to a lack of nutrients, improper watering, or too much (or too little) light, there are many possible reasons. What matters is that you take a close look and avoid blindly adding fertilizer or moving the lamp without understanding the issue.
In this article, I’ll show you the possible causes of yellow leaves—and what you can do to help your plant recover quickly. With the right knowledge and a bit of intuition, you’ll have things back under control in no time.
Yellow leaves can be a subtle cry for help from your cannabis plant—and often, a classic problem is behind it: nutrient deficiency. Especially when there is a lack of nitrogen, potassium, or magnesium, the plant visibly suffers. Nitrogen ensures strong leaf growth, while potassium and magnesium are essential for photosynthesis and energy production.
If any of these nutrients are missing, the plant gradually loses its healthy green color—clearly showing you that it needs support.
What should you do? Don’t just reach for fertilizer at random; take a close look first. A balanced nutrient mix is essential. If you suspect a deficiency, you can make targeted adjustments and then observe how your plant recovers. Often, just a few small corrections are enough to get it back into top shape.
Water is life—but only in the right amount. Cannabis plants are quite sensitive: If you give them too much, their roots end up literally sitting in water and can't get any air. The result? Nutrient uptake drops off, and the leaves start turning yellow.
But the opposite extreme—not enough water—also puts the plant under a lot of stress. Dried-out roots can't function either, and this too shows up in the leaves.
What helps? Make sure to water your plant in a balanced way. The soil should always feel moist, but never soaking wet. A good tip: Always let excess water drain away—this helps prevent root rot and gives your plant exactly what it needs to stay healthy and green.
The soil pH value is crucial for the plant’s ability to absorb nutrients. If the pH value is outside the optimal range (between 6.0 and 7.0), nutrient lockout can occur. In this case, nutrients are present, but the plant cannot absorb them, which can also lead to yellow leaves.
Solution: Regularly check the soil pH value. If it is not within the optimal range, you can adjust the pH with suitable products to ensure the plant can absorb nutrients.
Auch Schädlinge wie Spinnmilben, Thripse oder Blattläuse können dafür sorgen, dass die Blätter gelb werden. Diese kleinen Insekten saugen den Pflanzensaft aus den Blättern und schwächen so die Pflanze. Darüber hinaus können Krankheiten wie Wurzelfäule oder Pilzinfektionen zu Vergilbung führen.
Lösung: Kontrolliere Deine Pflanzen regelmäßig auf Schädlinge. Bei einem Befall können spezielle Schädlingsbekämpfungsmittel oder natürliche Feinde wie Marienkäfer helfen. Bei Krankheiten solltest Du die befallenen Teile der Pflanze entfernen und die Umgebung optimieren, um die Ausbreitung zu stoppen.
Cannabis plants need plenty of light to grow healthily. Lack of light can cause the leaves to turn yellow because the plant cannot produce enough energy through photosynthesis. Other environmental factors such as extreme temperatures or excessive humidity can also cause stress, which may result in yellow leaves.
Solution: Make sure your plants receive enough light, especially during the Flower phase. Also, monitor the temperature and humidity levels in your grow room to ensure optimal growing conditions.
Removing yellow leaves from cannabis plants is not always immediately necessary. It depends on how severely the leaves are damaged and what stage your plant is in. Yellow leaves can stress the plant and reduce the energy it needs for flower production. However, there are a few things you should consider before reaching for the scissors.
If the leaves are completely yellow and show no green areas, they have lost their function and no longer contribute to the plant’s energy production. In this case, it makes sense to remove them to relieve the plant and improve airflow between the leaves, which can help prevent mold and fungal infections.
Solution: Carefully cut off yellow leaves with clean scissors or a knife so the plant can focus on its healthy parts.
Slightly yellow or partially yellowed leaves may still contain nutrients that the plant can use. Especially during the growth phase, it is advisable to leave the leaves on the plant as long as there is still some green present. They can still contribute to photosynthesis and provide energy to the plant.
During the flowering stage, it is normal for some older leaves to turn yellow as the plant focuses its energy on flower development. In this phase, you can regularly remove yellow leaves to direct the plant’s resources toward flower production and keep it healthy.
When cannabis develops yellow leaves shortly before harvest, this is often a completely natural process and not a cause for concern. In the final stage of growth, the plant focuses its energy on the Flowers, which means it transports fewer nutrients to the leaves. As a result, the leaves turn yellow, especially the older, lower leaves.
During the last weeks before harvest, the plant largely stops taking up nutrients. It begins to use the nutrients stored in the leaves to supply the Flowers. This process of nutrient redistribution causes the leaves to lose their green color and turn yellow. It is a sign that the plant has reached its ripening phase and harvest time is near.
In most cases, you do not need to take any action if your cannabis plant develops yellow leaves shortly before harvest. It is a natural part of the ripening process. However, removing the yellow leaves can improve airflow around the Flowers and help prevent mold, especially if you are growing in a humid environment.
If your cannabis plant develops yellow leaves with brown spots, this can indicate a more serious problem than just a simple nutrient deficiency. This combination of symptoms often points to a potassium deficiency or another form of nutrient lockout. However, there are also other possible causes, such as over-fertilization, pH issues, or even pest infestation.
A common reason for brown spots on yellow leaves is a lack of potassium. Potassium is an important nutrient responsible for regulating the plant's water balance and nutrient uptake. A potassium deficiency often causes the leaf edges to turn yellow and brown, dry spots to appear.
Solution: Use a fertilizer with a high potassium content to correct the deficiency. Also, make sure the soil pH is in the optimal range (6.0–7.0 for soil) so the plant can absorb potassium.
Sometimes the necessary nutrients are present in the soil, but the plant cannot absorb them due to an incorrect pH level. Soil that is too acidic or alkaline blocks the uptake of potassium and other nutrients, which results in yellow leaves with brown spots.
Solution: Check the pH level of your soil and make sure it is within the optimal range. If needed, adjust the pH to improve nutrient absorption.
Another possible issue is overfertilization. Too much fertilizer can damage the roots and lead to a buildup of salts, which in turn hinders nutrient uptake. This can cause yellow leaves and burned brown spots.
Solution: Flush your plants with clean water to remove excess salts from the soil. Reduce the amount of fertilizer and only use as much as the plant actually needs.
Spider mites or other pests can also leave brown spots on the leaves. These tiny insects suck the sap from the leaves and leave behind yellow to brown spots that get larger over time.
Solution: Carefully inspect your plant for pests. If you find any, take action immediately, for example by using biological pest control agents or natural predators like ladybugs.
Our best THP420 strains Toda
Yellow leaves are a clear sign that something is wrong. Common causes include nutrient deficiencies (such as nitrogen, potassium, or magnesium), overwatering or underwatering, poor lighting conditions, or an incorrect soil pH. It is important to identify the exact cause in order to take targeted action.
A typical sign of nitrogen deficiency is a uniform yellowing of the lower leaves, while the upper leaves remain green. If magnesium is lacking, yellow spots appear between the leaf veins, while the veins themselves stay green. Potassium issues often show up as yellow, brown, or burnt-looking leaf edges.
First things first: Stop watering! Let the soil dry out thoroughly and make sure there is enough ventilation. In the future, only water when the top layer of soil feels dry. Good drainage in the pot also prevents waterlogging and protects against root rot.
Most of the time, unfortunately not—once leaves have turned yellow, they usually do not recover. However, if you have addressed the underlying cause, new growth should appear healthy and green again. That’s why it’s important to act quickly to prevent the plant from deteriorating further.
