Cannabis Leaf Curling – What Are The Causes? How to Beat “The Claw”

It is never a good sign when the jagged edges of cannabis plants take on a “canoe” shape and curl upward. In the immortal words of Jim Carrey, “It becomes the claw!” So what causes cannabis leaves to pucker? Well a lot of things.

Although cannabis is a hardy and resilient plant, it is still prone to a fair share of pests and problems. Unfortunately, it’s only part of the deal. As you gain experience, you will be able to identify the main problems contributing to the claw sooner.

Claws is a common language for curling the leaves of a cannabis plant. When the leaves of a cannabis plant curl, it is often a distress signal. Many variable factors can contribute to clawing and they are important to address. Otherwise, you risk slowing growth or even losing the plants. Pause your freaking out. If you have a few curly leaves, it’s game not over. Here’s a look at five of the most common culprits behind curly cannabis leaves, also known as the dreaded “claw,” and how to fight them.

5 reasons your cannabis leaves are puckering

Overwatering your cannabis crop

Making sure you don’t overwater is the first step in diagnosing the cause of the clawing. Overwatering carries the risk of drowning and bud rot of the plant, while creating an ideal environment for the parasite that multiplies root rot, pythium. Both waterlogging and root rot cause the cannabis leaves to curl. Overwatering is one of the most common problems growers just starting out with, and luckily, it’s easy to fix.

Before you reach for the watering can, check your plants! Look at the leaves and the ground. When the leaves are drooping and appear to be growing slowly and the soil is dry, an inch or more, and you have the green light to water. Otherwise, it’s best to hold back. Overwatering is generally more damaging to your plants than lightly underwatering. If the leaves perk up within about 30 minutes of watering, then the underwatering was your culprit.

If you have an overwatered plant on your hands, let it dry for a few days and adjust your watering schedule accordingly. Another high-tech option for checking plant moisture is using a moisture meter. Like a thermometer, a moisture meter measures the water saturation of your plants from the root up.

Over-fertilization of cannabis plants

Overfertilization can cause a variety of problems. Nitrogen is essential for your plants to thrive. But as with water, there is too much of a good thing. Excess nitrogen in particular leads to nitrogen toxicity and consequently your cannabis leaves will pucker. This problem is known as nutrient burning and is another fairly common problem among hobby growers. Leaves curling from nutrient burns are usually accompanied by a deep green hue or even brown “burned” edges on the leaves. Fortunately, this is an easy fix too.

Once you’ve isolated a nutrient burn as the culprit behind your curls, you should start by rinsing with mildly acidic water with a pH of around 6.0. Douching should help get rid of excess nutrients near the roots and your plants will level out within a few days. Remember, you should maintain a stable pH. With Hydro, the pH should be between 5.6 and 6.5. In the soil, the pH should be between 6 and 7. Testing your pH is easy with a test kit.

Heat stress

Cannabis plants should be kept at 23 ° C (or 75 ° F), whether indoors or outdoors. At temperatures above 27 or 28 ° C, the plant loses water faster than it can replace it in the root system and therefore experiences heat stress.

The first sign of heat stress is slow growth, leaves tanning, and puckered or “canoeing” fan leaves to retain moisture. A robust root system can partially alleviate heat stress, but even a short episode of high heat (summer 2021, a lot?) Is enough to permanently damage the fan leaves.

The solution, obviously, is to lower the temperature in the grow room. Easier said than done for indoor growing setups. You will know that heat stress was causing your leaves to curl when you discover new growth within a few weeks.

Windburn

Ventilating your grow space is important, but too much wind (see a little pattern here?) Directly on your cannabis plants could be one of the reasons your cannabis leaves are curling up.

If you’re using fans in an indoor grow room, turn them down a little or make sure they’re angled away from the plants and not hitting them directly. If you are growing outdoors, you may need to move the plants indoors once they are potted.

Light fire

Heat stress and minor burns can sometimes go hand in hand, but you can still encounter minor burns even at ideal temperatures. Mild burns are more common indoors, usually when the plants are too close to the grow lights. As with heat stress, the frizz usually occurs towards the top of the plant or whichever part is closer to the light source. With a slight burn, the leaves begin to turn yellow and eventually curl up. If you have minor burns, move your plants further away from your light source and they should recover.

What other growing tips would you like us to cover? Let us know in the comments! For the latest cannabis coverage, news, and more, follow CLN.