cannabis leaves curling up on edges

Why are Leaves Curling or Clawing? (“The Claw”)

The following symptoms are for when your cannabis leaves are “clawing” or curling up or curling down. Sometimes known as “The Claw”. I’ll give a short explanation with pictures of each problem, plus links to the solutions! Fix this common (but hard to diagnose) marijuana problem today!

Nitrogen Toxicity

A Nitrogen toxicity is the result of the plant getting too much Nitrogen (usually from too high levels of nutrients overall, or by using a Vegetative nutrient in the flowering stage). It causes dark green leaves and curled tips (“the claw”).

One of the main symptoms of a Nitrogen toxicity is curled tips (“the claw”)

A plant with a Nitrogen toxicity tends to be dark green all over

Wind Burn

Caused by too much wind. You’ll notice that the leaves further from the fan don’t have symptoms.

Example of too much wind on your leaves

Bad Soil / Overwatering / Underwatering

You can help prevent over and under-watering your cannabis plants by always starting with good soil or coco coir.

Bad Soil

Bad soil is usually thick and muddy. Plants in poor soil will droop (often with unhappy curly leaves) no matter your watering practices.

Avoid thick soil that stays wet for a long time and doesn’t drain well


Overwatering makes leaves fat with water, and they tend to curl down and droop

Overwatering (especially when combined with heat) can also cause leaves to curl up

This plant was grown in muddy soil, and the curling, unhealthy leaves kept getting worse and worse over time!


Underwatering causes symptoms that often look like overwatering, but you’ll know it’s underwatering if the plants perk up each time after you water them.

Root Problems

Although often caused by overwatering, once the roots are sick you’ll see symptoms for a little while even after you start watering your plants properly.

Unhealthy roots can cause all sorts of problems including curling and clawing!

Unhealthy Roots in Soil/Coco

This plant’s roots were damaged from being overwatered and too hot for several days. As a result, the leaves took on a strange, blistery appearance.

This plant suffered from heat combined with overwatering for several days. This damaged the roots and gave it this odd leaf curling.

Root Rot

Root rot is something marijuana hydroponic growers can suffer from if pathogens attack the roots. It is often triggered by heat and/or lack of bubbles near the roots.

Root rot can cause curling leaves and brown patches as well as sometimes other nutrient deficiencies


If a plant stays in the same container for too long, the roots will eventually start wrapping around the edges of the pot. This is known as being “rootbound” and causes symptoms similar to other root problems.

A rootbound plant has been in the same container for too long. Roots wrap around the edges and “choke” the plant.

Rootbound plants often droop, appear yellow, get nutrient deficiencies, and stay small. Even if you’re caring for them perfectly!

If you see tons of white roots when transplanted, that means the plant was in that container too long

When this happens, the main solution is to transplant the plant into a bigger container. Another solution is to grow in fabric pots or air pots. These types of pots let air in from the sides, killing the circling roots (“air-pruning” them) and prevents the plant from getting rootbound for months.

To help a rootbound plant, transplant to a bigger container with fresh potting mix

Or start with air pots or fabric pots in order to prevent plants from getting rootbound at all

Heat Stress

If plants are experiencing a lot of heat, it can make leaves droop and/or curl. Some strains can handle a lot of heat, while other strains tend to droop when it gets warm.

Heat can cause leaves to curl up

Read more about heat and growing weed:

Light Burn

Plants can get light burn (sort of like a sunburn) even if the temperature is completely under control. The symptoms are usually concentrated close to the grow lights. Sometimes this can cause leaves to claw and curl downwards.

Light burn can cause the leaves closest to the light to turn yellow

Bugs & Pests

Often a bug infestation caused general plant unhappiness, but these are some of the most likely to cause curling or clawing leaves.

Broad Mites

Usually, you can’t see broad mites because they live inside the plant. The main symptom of an infestation is strange leaf curling that is specific to this pest, as well as “wet” looking leaves.

Hemp Russet Mites

Hemp russet mites can also cause drooping and other strange symptoms, but the bugs are so small many growers don’t realize what they’re dealing with.

Hemp russet mites cause drooping and yellow mold-like growth on the tops of plants

A closeup of the hemp russet mites

Fungus Gnats

Fungus gnats look like tiny flies buzzing around your topsoil. Although a few fungus gnats won’t really hurt your plants, a big infestation can damage the roots, causing symptoms similar to other types of root problems.

Learn about the various things that cause cannabis leaf curling or clawing, and get the solutions!

leaves edges curling up! pics.

Premium Member
Snow Crash

Textbook potassium deficiency actually.

Potassium is a very important element for the mobility of a variety of elements, energy, and water. When it comes to transpiration (sweating) of the leaves to help them stay cool this is the most important nutritional element.

As a cation potassium will compete for uptake (osmosis) with other cations. Calcium, Magnesium, and Sodium are generally the cations that will skew the uptake of Potassium. Excesses of anions like sulfates, phosphates, and nitates, can cause precipitation of Potassium based salts. Balance is key.

During instances of high heat and high humidity the plant feels the same way you do, like you just cannot cool off, the water just doesn’t do much evaporating and cooling. The plant works and works to push the water out and shapes itself that way to help stay cool. In very low humidity and high temperature the plant will be transpiring as quickly as possible because the water evaporates right off so fast that it’s practically being pulled out (like growing in a dehydrator).

No matter how you carve it, high or low RH, it’s always the heat that increases the need for transpiration and the need for Potassium. Add in a salinity issue and things can get bad fast.

In this case the slight yellowing of the leaves near the edges and the curl of the leaf it would appear there is most definitely a potassium issue, in addition there may be a too high N too low P problem going on.

My suggestion here is to cut way back on the Cal-Mag Plus or other calcium nitrate based supplement if you’ve been using it. With the next 2 or 3 feedings you’ll want to get a good 1:1 runoff ratio (4 gallons in, 2 gallons out) to ensure that build up is not a contributing factor.

In addition, with these feedings you’ll want to do a little tweaking of the npk ca/mg profile. My suggestion is to use a kelp extract or other “stress reduction” kind of B-vitamin/auxin/cytokinin supplement. Things with Yucca, kelp, and fulvic acid will help your plant rebound from the stress. These supplements are usually naturally high in Potassium and I’d be using something like Liquid Karma and MaxiCrop/Nitrozyme/Seaplex/BioWeed at full strength. Do it with the first watering, then on the third watering. A few tablespoons of a higher pk composted fertilizer amended into the top soil is probably all the other “nutrient” fixing I would want to do. Keep it organic, you know?

Then, just keep your eye on the pH and top dress with a little dolomite every few weeks to keep your micro-buffer balanced. If all this curling is recent damage since they’ve been under the 1000w and the heat from it then once the light is backed off, and the plants rebound, and you move them outdoors. They’ll be fine.

Don’t do anything drastic. Just address the deep lush blue/green look to them (indicating the N:P issue) and make sure to replace that potassium your plants have been burning through. Easy peasy.

was wondering if anyone had any ideas? everything has been fine and the plants still look happy but theres this curling upwards of the leaf edges on the… ]]>