Weed Leaves Turning Yellow: Tips on Analyzing Your Plant and Choosing Treatments

You’re undoubtedly terrified right now of your weed leaves turning yellow. If you are worried about the question “why are my marijuana leaves turning yellow”, then this article is for you. Here you will find all the useful information about why weed plant leaves turn yellow.

The first step, however, is to appropriately diagnose the problem. We need to understand why weed plants turn yellow. There are many reasons why marijuana plants have yellow leaves.

Here’s a rundown of some of the most common reasons why weed plants droop and turn yellow, as well as some potential ways to help you repair it. So, let’s understand so that you no longer ask “why are my weed leaves turning yellow?”.

Yellowing Leaves on Weed Plants? How to Obtain an Accurate Diagnosis

Chlorosis is the scientific word for the yellowing of leaves. Plant leaves lose their chlorophyll as a result of this process (the compound that keeps them green).

Chlorosis might be the consequence of a specific condition (environmental issues, lack of sunshine, etc.) or it can simply be the result of senescence (the process of change that occurs as a result of biological aging).

Natural aging is nothing to be concerned about. In reality, many plants in a crop will turn yellow and remove their leaves after each growing season (think of deciduous trees during autumn). At this stage in the growing process, some farmers “flush” their crops with clean water or a flushing solution. This aids in the removal of any extra nutrients, as well as hastening the natural aging process.

Other things, of course, might be to blame for the yellowing of your marijuana crop. Chlorosis, on the other hand, is rarely a reason for alarm. Photosynthesis is frequently hampered by something simple. You can usually assist your plants to recover without trouble if you act promptly.

Let’s look at some diagnostic tools to see if they may assist you to find out why do weed plants turn yellow

marijuanas plants yellow leaves

Light Deficiency

Lighting is a difficult subject to grasp, especially for rookie growers. You must first choose the proper sort of illumination, and then determine the best distance between your plants.

Your plants require light for photosynthesis, thus they are essential. The appropriate quantity of light is very critical for seedlings to stimulate them to thrive. Young cannabis plants will turn yellow if they don’t receive enough light, whereas adult plants will darken if they don’t get enough.

Check the nodal spacing (stem stretches between the leaves) of the newer/smaller leaves on your plants to see whether a light deficit is an issue. Inadequate light may be the cause of more than one leaf-width of spacing between leaves.

The Fix

Cannabis seedlings benefit from bright lighting such as HID (high-intensity discharge) bulbs. For the greatest effects, use metal halide (MH) or high-pressure sodium (HPS) lighting. LEDs are a good option in a smaller grow room when heating is a concern. You may also consider lowering the lights so that they are closer to your plants. However, when the plant grows higher, you’ll need to relocate them.

Watering Issues

Chlorosis may be caused by both over-and under-watering cannabis plants. Water, unfortunately, is a difficult thing to do correctly. You must water your crop in the correct amount and at the appropriate times.

Too much water can deplete the oxygen supply in the soil, starving the root system and resulting in mortality. Your plants’ leaves will be bloated, drooping, and maybe yellow if you’ve over-watered them.

Because most planters are acutely aware that their crop may perish if it is not properly hydrated, under-watering is less usual. However, under-watering does occur, and under-watered plants may seem fragile, thin, brittle, and yellow.

The Fix:

The remedy is simple: cease watering over-watered plants and increase irrigation of under-watered crops! Learn everything you can about your plants, as well as the habitat in which they grow. Get a sense of how heavy the growth media is when it’s dry and when it’s wet. You may also buy a humidity meter to get a better idea of how much water is in your soil.

(By the way, bad soil/growing medium can also cause watering problems.) Make sure you choose drainage-friendly soil and containers).

pH Imbalance

pH stands for potential hydrogen and is a measurement of a medium’s acidity. pH is measured on a scale of 1 to 14, with 7 indicating neutral. The pH of your soil should be between 6 and 7 for cannabis plants (hydroponic growers should opt for 5.5-6.2).

Your plants won’t be able to get the nutrients they need if the pH isn’t suitable, and their leaves may discolor. (We’ll go through vitamin shortages in more depth later, but keep in mind that pH imbalance may produce a wide range of symptoms.) A pH imbalance is indicated by yellow leaves, burning at the margins, and signs such as spots and stripes.

The Fix:

To evaluate the quality of your growing media, you may purchase a pH tester online. Home kits, on the other hand, don’t always test for calcium carbonate, which might cause your soil to be too alkaline. You may test for it by putting a sample of soil in a cup of vinegar and seeing if it fizzes; if it does, it’s calcium carbonate. Send a sample to a lab as an alternative.

You may either re-pot in a fresh growth media or modify the soil pH once you’ve identified the issue. The pH of several compounds is known to vary. Wood ash and lime, for example, can boost it. However, purchasing pH UP and pH DOWN items from a gardening store are probably a lot easier.

Heat Stress

If plants are maintained too close to a light source, heat stress can result in yellow, burned leaves. Some leaves may begin to curl as well.

This, for want of a better explanation, is because marijuana plants (like other plants) are sensitive to temperature extremes. And, once again, it’s usually a lighting issue.

The hand test is a fast approach to determine whether heat stress is a problem. Hold your hand in front of your plants for thirty seconds. It’s too hot for your weed if it’s too hot for your hand!

The Fix:

Ascertain that the light source is at the proper distance from your crop. As the plants develop, you’ll need to keep an eye on them and make changes as needed. A thermometer is also a good investment. If it’s too hot, turn on the air conditioner or turn on the fans.

Heat-stressed plants may need to be relocated away from the light source. Keep them at a safe distance until they start to feel better.

Nutrient Deficiencies

All cannabis producers are concerned about nutrient shortages, but the last thing you want is for your plant to die as a result of one – after all, it’s something that can be easily remedied!

Yellow leaves are frequently caused by nutrient shortages. However, getting a precise profile of your soil content may need sending it out for testing. Here are some typical nutritional deficits to assist you to find out what your crop is missing:


Nitrogen is one of the most important plant nutrients for the formation of chlorophyll. As a result of the shortage of nitrogen, yellow leaves will develop. A yellow hue usually appears first in older leaves. Early blooming, and fewer buds are two other signs.


Another important vitamin is potassium. If it isn’t there, the fan leaves will become yellow with brown blotches. It’s also possible that some leaf tips will turn brown and dry off. Curling is also a typical symptom of a potassium deficiency.


Calcium is required for the construction of plants because it binds the cell walls together. Lack of calcium can cause slowed growth of new structures, as well as deformed root tips and early leaves.

The lower leaves will eventually curl and acquire yellow-brown patches.


Another ingredient that aids in the formation of chlorophyll is magnesium. Yellow veins appear in the fan leaves as a result of a lack of magnesium, and the leaves finally coil up and die.

The problem with magnesium shortage is that symptoms don’t manifest until four weeks after the plant begins to suffer from a deficit. Maintain a healthy magnesium level throughout your child’s development.


Although cannabis plants only require a little quantity of sulfur, a lack can be fatal. The most common reason is a high pH in the soil. Yellow fan leaves with stunted development and frailty are signs of a sulfur deficit.


This mineral, among other things, is necessary for the formation of chlorophyll. The wrinkling of the leaves indicates a zinc shortage. The leaves will frequently spin 90 degrees to one side. The veins of the leaves will turn a yellowish tone.


Even though iron is not a molecule found in chlorophyll, it is required for its production. The presence of an iron deficit can be detected by the yellowing of immature leaves. This discoloration will eventually spread to the veins of older leaves.


A lack of manganese in a plant’s root system might cause problems. It’s easy to spot since the older leaves become yellow.

The Fix:

Increase amounts of the nutrient(s) your plant needs by adding it to your soil or growth medium. To avoid nutrient shock, take it slowly.

Pests and Insects

Finally, bites from an insect infestation can cause yellow leaves on marijuana plants. The particular symptoms vary depending on the insect in question. Fungus gnats, on the other hand, are a common cause of chlorosis.

When you over-water your plant, these pesky insects will most likely arrive. The gnats won’t harm your plant directly, but the larvae will feed on the roots, causing the leaves to yellow.

The Fix:

Diatomaceous earth, neem oil, and other natural pesticides can be used to naturally kill insects.

Final Thoughts on Cannabis Yellow Leaves

weed plant leaves turning yellow

The first thing you should do if you notice yellow leaves on a weed plant is not to worry. Yellow tips on a weed plant aren’t necessarily a sign of impending doom. Even if there is no danger to your plant, the leaves might become yellow for no apparent cause.

In other cases, you may need to intervene to preserve your crop from extinction. It’s time to defoliate any leaves that are very withered and fragile (remove the affected leaves). Make sure you figure out what’s causing the problem, so you can fix it.

Hopefully, this tutorial has given you some helpful hints for preserving your prized cannabis plants.

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The content on this channel does not form a professional opinion, recommendation, substitute for consulting a specialist, or receiving medical advice. Cannabis is a dangerous drug, as defined in the Dangerous Drugs Ordinance, for all that assumes. Four Hundred and Twenty does not encourage or recommend consuming any substance and will not be responsible for any such use.


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