cannabis leaves curling upwards

Why Are My Weed Leaves Curling Up: Causes & Solutions

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Growing marijuana is truly a joy, well, except when you notice that your weed plants are having some health issues. There are many health issues which a weed plant can have. You might have noticed that your cannabis plant is suffering from leaves that are curling upwards, and possibly discolored too. (it’s well worth picking up this FREE grow bible, it has some great information).

So, why are my weed leaves curling up? Well, this could be due to a number of issues, and most commonly, under or over water your plant, giving it far too much nutrients, or excessive heat or cold are the main causes of curled up cannabis leaves, among others.

There are 6 main causes of curling up cannabis leaves, and today we want to talk about each of them, as well as the solutions to each problem.

Why Are My Weed Leaves Curling: Causes & Solutions

Ok, so there are a few different reasons why your cannabis plant leaves might be curling up, and they vary greatly.

Let’s go over the 6 main causes of curled up weed leaves, and what you can do to remedy the problems.

1. Excessive Heat or Cold

One of the issues which can cause your cannabis plant leaves to curl up is due to excessive heat. If your cannabis plants are in a grow room or an environment that is too hot, you will often see the leaves curl up and develop nasty looking brown fringes.

Most cannabis plants require the temperature to be well below 30 degrees Celsius, usually more like 27 or 28 degrees. Anything over 30 degrees Celsius can cause heat stress, which results in curled and yellowing or browning leaves, among a host of other problems. Simply put, your pot plant is burning up due to being too hot.

On the other hand, excessive cold has also been known to cause curly cannabis leaves. Pot plants should never be in temperatures below 12 or 10 degrees Celesius at the lowest.

If your pot plant is regularly subjected to excessive cold, the leaves can become very discolored, they can curl up, bud rot may develop, and eventually your plant will just die.

The Solution

The solution to these temperature issues can vary depending on what the exact problem is. Either way, you need to ensure that your grow room is at the right temperature to support healthy weed growth.

One thing to keep in mind here is that weed plants require different temperatures based on the stage of growth they are in, whether this be the seedling, vegetative, or flowering stage.

General speaking, the optimal temperature range for cannabis across all of the growth stages is between 10 and 28 degrees Celsius.

Cannabis Plants Are Too Cold

So, if the grow room you have your cannabis plants in is too cold, here are some solutions you can try to put into effect.

Increase The Amount Of Grow Lights

Increase the amount of grow lights you have present, or replace current grow lights with stronger ones. The more light you have being produced in the grow room, the hotter the air will get. Keep in mind that certain types of grow lights put out more heat than others.

Turn Down Ventilation

If you have a lot of ventilation going on in your grow room, try turning that down. You might have to insulate holes and cracks in walls or doors to reduce airflow and to stop heat from escaping. You might also have to turn down your fans and ventilation systems, or even turn them off for a few hours. The more air circulation there is, and the more air can get out, the cooler the grow room will be.

Increase The Amount Of Reflective Materials

Increasing the amount of reflective materials present in the grow room will help reflect more light, and therefore will also hold more heat in the grow room.

Move Your Plants (If Outside Growing)

If you are growing outside, you might just have to move your plants indoors during the night to stop them from being exposed to the cold.

Cannabis Plants Are Too Hot

Just like there are various solutions to increase the temperature in your grow room, there are also ways to decrease the temperature in your grow room. Here are some solutions you can try to cool down your weed plants.

Try moving the plants further away from the grow lights, especially if you have ones that produce a lot of heat. Alternatively, you can try replacing your grow lights with certain types which do not produce as much heat.

Increase the amount of ventilation and air circulation you have in the grow room. The more air circulation there is, the cooler the grow room will get, plus this will help provide your pot plants with more oxygen as well. To do this, you can turn up an air fan, add an air fan to the mix, add more ventilation systems, or maybe drill a couple holes in the doors or walls to let heat escape.

Something to keep in mind here is that you can always try planting you cannabis in white pots or buckets, as opposed to black ones, which will absorb less light and therefore keep the roots cooler.

2. Too Little Or Too Much Water

Yet another cause of weed leaves curling up has to do with improper watering practices. Both under watering and over watering can cause this to occur, although most of the time it is over watering.

Generally speaking, beginner cannabis growers give their weed plants way too much water, but too little is usually not an issue. Keep in mind that given the situation, both under watering and over water can result in weed leaves curling either up or down. It really depends on the exact situation you have going on in your grow room.

Under watering your plant can also result in severe dehydration, it can combine with strong lights to burn the leaves, and it causes your plant dry out.

On the other hand, over watering can cause the roots of your plant to rot, which then causes it to not be able to absorb nutrients as it should.

Overwatering can also cause pest infestations, mold, and fungus. Simply put, over watering your plants will cause them to drown.

The Solution

Ok, so the solution here is to start engaging in better watering practices, and this holds true whether you have been giving your cannabis plant too much or too little water. What you should do is the simple finger test.

If you stick your finger in the soil and you have wet soil sticking to your fingers, or if there is just a puddle of mud, it means you are over watering your plants. Let them dry out until the soil is quite dry until you water them again.

On the other hand, if you can stick your finger down into the soil a few inches and it is bone dry, you are under watering your plants. A good way to know if you are under watering your weed plants is if the leaves perk up right after you give them some water. (If you need some pointers on the right soil to use, checkout our epic guide here).

If you are under watering your plants, another solution may be too turn up the humidity a little bit, although this can be risky, as excessive humidity comes with its own issues.

3. Too Many Nutrients & Fertilizer

The next issue which can cause your cannabis leaves to curl up is if you are providing them with too many nutrients.

This tends to be the case mostly with nitrogen. Simply put, you could be poisoning and overwhelming your cannabis plant with too many nutrients.

This can then result in nutrient burn, often characterized by yellow, brown, and discolored leaves, combined with the curling up of the pot leaves.

The Solution

If you have been following the directions on your plant nutrient bottle in regards to diluting the nutrients in water, you want to cut back a bit.

For instance, if you nutrient bottle calls for 2 teaspoons of nutrients per 2 gallons of water, cut back to ¼ or ½ a teaspoon per gallon. You might even want to eliminate nutrients for a couple of days altogether and use only water for feeding, to see if the problem resolves itself.

If this works, remember to use fewer nutrients than before, or else the problem will just start up again (more on the ideal nutrients here).

4. Wind Burn

Yes, your cannabis grow room should have some fans or a decent ventilation system, but there is such a thing as too much of a good thing.

In this case, weed plants require a bit of a breeze and some air circulation, but too much can cause leaves to curl up and look like they are burning. This is called wind burn.

The Solution

The solution here is easy. Turn the fan down from the higher settings to the lower settings, and do the same with your ventilation system.

Moreover, try to aim the fan at a wall or just not directly at a weed plant. Even if you do not aim the fans at the plants, they will still create air circulation in your grow room.

If you are growing outdoors and it is excessively windy, you might just have to move the pot plants indoors.

5. Light Burn

Light burn is another thing which can cause your leaves to curl up. This generally happens at the top of your weed plants, and the closer to the light the plant is, the worse the problem can get.

Yes, weed plants need a lot of light, and some heat too, but once again, here we have the too much of a good thing problem again.

If you have excessively strong grow lights, too many of them, or depending on the type of light, if you have it too close to the pot plant, it can cause the leaves to burn, which is often characterized by the yellowing, drying out, and curling up of the leaves.

The Solution

The solution to this issue comes in a few different forms. If you have a super strong industrial grow light, chances are you need to switch it out for something a bit smaller that does not put out so many lumens and so much heat.

Here, you can also try moving your plants further away from the lights, although this may cause them to stretch. You can also try taking down some of the reflective materials you have outfitted your grow room with, just to cut down on the amount of light reflection taking place.

Whatever you can do to decrease the amount and intensity of light your cannabis plants are getting should be undertaken if light burn is the issue.

6. Bugs & Other Pests

The other cause of curling leaves could be bugs and pests. There are certain bugs and pests which are known to cause the curling of cannabis leaves.

Due to the root, plant structural, and photosynthesis issues which many pests can cause, depending in the pest and severity of the infestation, it can cause curled up leaves.

There are fungus gnats, spider mites, and other pests which can cause this to occur.

The Solution

This is a bit of a trickier problem to deal with, as different pests on your cannabis plants require different solutions, and often many solutions combined into one.

Using plant and people friendly natural pesticides, getting rid of severely infested plants, cutting off parts of the weed plant with severe infestations, and washing off your weed plants with various liquid mixes are all possible solutions to this problem.


Guys, if your cannabis leaves are curled up, it could be due to a number of issues, and each issue has various solutions you can try to put into effect. The point here is that you do need to get to the root of the problem as fast as you can, before it gets any worse, or else you risk the health of your plants, and of course the final yield and potency of your bud. Leave the problem for too long, and your cannabis plants might just die.

Here are the 6 main causes for your weed leaves curling up and the best way to fix the problems quickly with our helpful solutions guide.

What Causes Curly Cannabis Leaves And How To Cure Them

There are numerous reasons why you might find curly cannabis leaves in your grow-op. This guide will explain why this phenomenon occurs, and what you can do to prevent it from ruining your final product.


Cannabis plants can’t vocalise a call for help—but they can send signals to tell you all is not well. If you see leaves either clawing or curling, there is trouble with the trees. Don’t ignore their pleas. This blog will help you identify the causes and cures for curly cannabis leaves.


Overwatering will literally drown your plant’s roots. Excess water will not only rinse most of the beneficial microbes from the medium, a sodden substrate can also become colonised by algae and nasty fungi. Persistent overwatering invariably invites the parasitic Pythium, better known as root rot. Cannabis plants with droopy, claw-like leaves could be trying to tell you they are waterlogged.

“Water mould” microorganisms are just like vampires; you have to invite them in before they can do any harm. Keep them out of the garden by making sure they are not welcome. Maintaining an effective wet-dry cycle is all it takes. If you can pick up your pots, do it. Then you can tell by their weight when it’s time to water.

If you can’t lift the containers, then consider a moisture meter and make sure to carefully monitor post-watering plant behaviour. Try reducing the volume of water. Alternatively, take longer intervals between waterings. Unfortunately, Pythium is virtually incurable and will turn your plant’s roots into brown sludge. If you see droopy, curly cannabis leaves, especially with young plants, look to the roots for answers.


A heavy-handed approach to nutrients is ill-advised. Excessive doses of nitrogen-rich vegetative growth base nutes can cause clawing in leaves. Sometimes, they will even canoe. Similarly, overdoing it with the phosphorus and potassium during flowering will cause curly cannabis leaves and scorch the tips. Chlorosis is a common symptom in both cases.

Dial in feeding. Easier said than done right? Wrong! Almost every brand of well-known cannabis fertiliser offers a feeding chart free to download from their respective websites. Granted, not all cannabis varieties will respond in the same way to fertilisers.

It’s better to start low and go slow. You can incrementally increase doses without seeing leaves curling or clawing. But if you dive right in at maximum strength, you can expect plenty of curly cannabis leaves that will probably die and eventually drop-off.
It should go without saying, but we’ll say it again for good measure; make sure the nutrient solution is the right pH. That’s about 6.0pH for soil and a more precise 5.8pH for coco/hydroponics.


Heat stress can occur indoors or outdoors. If you see curling and nasty-looking brown fringing, your cannabis leaves are sending you a distress signal. Cannabis plants can photosynthesise efficiently at moderate temperatures up to 28°C. Anything above 30°C and your plants are in the danger zone. Combine this with low RH and you’ve got real problems. New leaves will grow gnarly and old leaves will curl yellow and maybe even burn to a rusty, brown crisp.

Indoor growers must constantly maintain the optimal environmental conditions. This starts with optimal light distance. The only way to keep the plant canopy in the sweet spot is to measure and adjust until mature plants peak in height during mid-late bloom, depending on the strain. Moreover, indoor growers can utilise air-con and fans to keep the grow-op cool.

Outdoor growers confronted with heat waves and drought conditions have less control than the indoor grower. Constructing a simple screen shade will keep plants slightly cooler and may prevent leaves from fraying and curling further. You can’t really revive scorched leaves and will have to remove older foliage beyond saving. Also, planting in white pots instead of black pots will keep the root zone cooler.


Cold temperatures can cause curly cannabis leaves too. Eventually, all kinds of leaf discolouration will develop. Sure, cooler nighttime temps late in bloom can add a dash of purple charm to buds, but prolonged exposure to temperatures below 10°C will kill your plants. Flowers will be loose and leafy if plants even make it to harvest. Coupled with high RH, buds will be moist and become vulnerable to Botrytis, AKA bud rot.

Indoors, if temps are too low, you can always add more grow lights and turn a negative into a positive. Outdoor growers might consider an early harvest, or if possible, moving plants indoors at night. Cannabis is a hardy plant species, but outside of the optimal 20–28°C temperature range, leaves will curl or claw.


Genetics are the cause of all kinds of cannabis leaf deformities and mutations. Some strains occasionally have a tendency towards curly leaves or other odd traits. Most growers will thin out these plants. All the shrewd cultivator can do is write it off as bad luck.

Sativa strains and many autoflowering varieties are sensitive to high doses of fertilisers. This is a trait that can cause problems for beginner growers. The solution is to research your reefer. Always find out as much as you can about the genetics of a strain before you decide to grow it. Curly cannabis leaves can be completely avoided if you know how to keep your plants healthy.

Cannabis leaves curling or clawing are signs your plants are suffering. Something is going wrong in the garden. This blog will help you save the stash.