Cannabis Leaves Curling Up (Causes & Fixes)

One of the biggest problems that newbies find with their marijuana plants is curling or clawing of the leaves on their plants.

It’s often referred to as “the claw.”

While these issues are common, they are often hard to diagnose.

However, armed with the right knowledge, you’ll be able to spot the cause and remedy it.

Some of the most common causes for curling or clawing of leaves are overwatering, nitrogen toxicity, windburn, and bad soil.

In the following guide, we’ll take a closer look at some of these causes and exactly how you can fix them.

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How To Fix Curling Or Clawing Cannabis Leaves?

Although cannabis plants are not able to vocalize help when they need it, they will send you some signals to tell you that all is well.

So if you notice leaves are curling or clawing, then this means that your plants are in distress.

So don’t ignore it and try to get to the root of the problem immediately.

Perhaps the only way to fix curling or clawing leaves is to figure out the exact cause and find a solution.


One of the most common causes of curling is overwatering. Ultimately, what this does is naturally drown your plants.

The excess water rinses away most of the beneficial microbes from the medium.

A sodden substrate can become colonized by nasty fungi and algae.

Ultimately, if you indulge in persistent overwatering, it will also invite Pythium to take root, and this leads to the more common problem known as root rot.

If this is the case, then the plants will look, droopy, leaves will be curling, and this ultimately means that they are overwatered.

So the solution to this problem is to keep microorganisms such as water mold out your marijuana garden and as far away as possible.

You can start by maintaining an effective way to dry- cycle. Ultimately one of the most effective ways of determining whether your plants need to be watered is by picking them up and feeling the weight.

If you cannot move the containers, then consider investing in a moisture meter to monitor overwatering and plant behavior. You can also try to reduce the amount of water you use each time and wait for longer periods of time between waterings.


Cannabis Fertilizer

Over-fertilization is another common cause of curling. Ultimately, if you have a heavy-handed approach to nutrients, then this is going to be a problem.

Your constant need to excessively dose your plants will ultimately lead to curling. Sometimes they may even canoe.

Don’t overdo it with the phosphorus and potassium during flowering, as this will lead to curling cannabis leaves and scorched tips. Ultimately, in both cases, Chlorosis is a common symptom.

So to remedy this problem you can dial in feeding. Most retailers of cannabis will provide feeding charts that you can download from respective websites.

Not all cannabis varieties are equal and will respond in the exact same way; however, you still need to refer to the chart as a guide. So the rule of thumb is to start low and go slow.

Gradually you can increase the doses for as long as you don’t see the leaves curling. So the best thing to do is not to dive right in at maximum strength as this will eventually cause your marijuana plants to die.

Your plant’s nutrient solution should also have the right PH, which is 6.0 pH or 5.80 pH if you’re using hydroponics.

Heat Stress

Heat stress is another common cause of curling. If you see leaves turning brown around the edges, then it is a sure sign of heat stress.

Ultimately, cannabis plants need to photosynthesize effectively at temperatures up to 20°C and anything over 28 degrees Celsius will place your plants in danger.

So you can start by maintaining optimal environmental conditions. This means starting with optimal light distance. Indoor growers should also make use of fans and aircon to keep the growing area cool.

Low Temperatures

Likewise, if the temperatures are too cold, it’s going to still lead to clawing. All types of leaf discoloration will also develop from the symptom.

Ultimately prolonged exposure to low temperatures under 10 degrees celsius will kill your marijuana plants eventually, flowers will also be loose and leafy even if they make it harvest.

So what you can do is adjust your indoor temperatures if they are too low. One solution is to add multiple grow lights.

If you’re growing weed outdoors, you should consider an early harvest or moving plants inside at night.

Although cannabis is quite a robust species, temperatures should always remain between 20-28 degrees celsius in order for them not to curl and remain healthy.

What Causes Curly Cannabis Leaves?

Cannabis Leaves

Curling cannabis leaves are caused by many different issues that your marijuana plants could be experiencing.

Aside from the reasons that were already mentioned, including overwatering, over-fertilizing, heat stress as well as low temperatures, it could also be due to nitrogen toxicity.

Nitrogen toxicity basically is when plants get too much nitrogen. Ultimately it could also be due to high levels of nutrients.

And what it does is cause dark green leaves and curled tips. Ultimately, curled tips are the main symptom that you will notice if your marijuana garden is suffering from nitrogen toxicity.

Windburn is also another issue, and this is caused by your plants getting too much wind. If you’re growing your garden indoors, you’ll notice that the leaves that are farther away from the fan do not have these symptoms.

Bad soil is not also another reason why leaves will curl. If you have bad soil or if you are growing your marijuana in thick and muddy soil, leaves will eventually droop and curl irrespective of how good our watering practices are.

Under-watering causes symptoms very close to the symptoms of overwatering; however, you will notice that underwatered plants perk up each time that you water them.

Root problems are usually caused by overwatering, and once the roots are sick, the symptoms will remain for a while, even though you start watering your plants properly. Unhealthy roots can cause various problems including curling.

If your roots are damaged in any way, you’ll notice that your marijuana leaves start to curl and take on a strange blistery appearance.

This could either be from root damage and, in some cases watering as well as heat stress. Ultimately, it leads to leaf curling.

Root rot is another common cause of curling leaves. Marijuana hydroponic growers tend to suffer from this problem a lot.

It’s often triggered by heat, as well as a lack of bubbles in the roots. Leaves also take on brown patches that indicate deficiencies in the roots.

Light burn is another issue. Even if the temperature is completely under control, it’s quite possible for your leaves to experience light burn.

This is especially if you are growing indoors, and your plants are too close to grow lights. Ultimately, the leaves that are closest to the light will start to turn yellow.

Bugs are not the common cause of leaf curling. Bugs such as broad mites are hard to spot since they live inside the plant. However, if your marijuana gardens are infested with these mites, the leaves will look curled and wet.

MG Deficiency Of Cannabis

Cannabis MG Deficiency

One of the things that stunts marijuana growth is magnesium deficiency.

Irrespective of whether it is the vegetative growth cycle stage or flowering stage, this is a deficiency that no marijuana grower wants to experience.

However, magnesium deficiency can be avoided if you know exactly what to do.

You first need to start by identifying it. Magnesium deficiency is when there is a bottom-to-the-top nutrient imbalance in marijuana.

Plants will look unhealthy, and ultimately, it is the oldest or lowest leaves that will show deficiencies in magnesium. But leaves often turn yellow, and tips will dry out and become crunchy.

Since magnesium deficiency is mobile, it will, unfortunately, spread up the plant if it is left to its own devices.

As this issue spreads to the shoots, it will eventually turn purple, and chlorosis will start to accelerate. Therefore your reaction time is crucial, and the determining factor in whether your plants make it.

If you are a newbie, you’ll probably be rushing off to apply a quick fix of nutrient doses. However, this condition tends to lead to nutrient lockout.

Irrespective of the medium with the growth stage, yellow leaves, and brown spots starting from the bottom and moving up are a sure sign of magnesium deficiency.

Ultimately magnesium deficiency is a micronutrient deficiency, and these problems always start from the bottom and work their way up.

What you can do to solve the lack of macronutrients or magnesium deficiency is to start by adding supplements or a flush of 6.0 pH water. Ultimately this will work fine for all substrates.

Next, you need to prepare a feed with the maximum pH for your growing medium. You can also use the base nutes for cannabis-specific needs and micro and macronutrients that are high-quality as well.

Try potting up from smaller containers that have lightly filled soil to larger containers that have time-released fertilizers and soil mixes.


Curling in cannabis leaves is never a good sign. However, when beginning a marijuana garden, you should expect and be prepared for these things to happen.

Ultimately as a marijuana grower, the best thing you can do is to act quickly and provide the most appropriate solution in order to save your garden and eventually reap high-quality yields.

James Alexander James Alexander
Hey, I'm James! The founder and head writer here at I started this site to share my passion and knowledge of all things cannabis. I used to work as a budtender in central Amsterdam, and have over 7 years of growing experience.

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1 thought on “Cannabis Leaves Curling Up (Causes & Fixes)”

  1. Hi James
    This is my first grow, growing outdoors. Have 2 plants side by side, one plant has slightly curled edges the other is perfect. Both plants are 8 weeks old and almost 6’ in height. Divorce Cake strain. Why is only one experiencing curled edge. They are planted in the ground and have been absolutely thriving. I have been watering every 3rd day, checking with moisture meter all the time, watering has been perfect. Perhaps my feeding fertilizers is to much? Thanks


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