Marijuana Leaves Curling – How to Fix Them

Curling marijuana leaves

Here’s some general life advice: nothing good ever comes from things with claws.

Big scary scratchy animals have them and even sometimes normally-cuddly kitties will display them when provoked.  Movie monsters generally have some sort of claws. And, if you’re not careful with your growing techniques, your cannabis plants can have them too.

‘Clawing’ is one of the terms used to describe how plants can show their distress if something is wrong in their growing environment.

It can also be called curling, which is what happens when the tips of the leaves or even the whole leaves start moving up or down. Curling is one sign of a problem, and another is discoloration from stress in the tips of the leaves or even the whole leaf.

Unfortunately, as longtime growers know, there isn’t an easy solution to stop clawing, since the reason for this problem could be due to several factors. But with some observation and trying different techniques, you can learn what’s happening and how to make sure your plants grow better.

Possible reasons and solutions for curling

Fertilizer

Overfertilizing your plants can cause a host of problems. For instance, too much nitrogen can lead to leaf curling. Other ingredients in excess can lead to this phenomenon, including vitamins or minerals.

Not enough nitrogen can cause curling.

It can be easy to get to this point if you’re new to growing or are trying to take care of multiple types of plants that may all have different growing nutrient needs, such as light levels, humidity, and what medium to grow in.

To better dial in how much fertilizer you’re giving them, it helps to create growing and feeding charts, where you write down when you feed them, what you feed them and how much. Most fertilizer brands also include this type of information based on different quantities.

A good rule of thumb is to use a ‘low and slow’ method to see the initial effect, and slowly increase the amount. Check leaves daily to see any changes. Measuring the pH levels can also indicate if the fertilizer balance is of: the ‘sweet spot’ is between 5.8 and 6.0 pH.

If you’re having challenges with traditional fertilizer, consider seeking out “dirt” optimized especially for cannabis growers. This often comes in organic varieties.

Temperature

Plants that stay too warm too long are prone to curling leaves along with the tips turning brown. It’s not easy to regulate that in an outdoor farm, but you can utilize various shade techniques or tools to block direct sunlight.

In indoor settings, it’s easier to simply turn the thermostat down and adjust airflow to keep plants cooler consistently. An air conditioning unit can help.

At the other end of the spectrum, plants that are too cool for too long can also suffer damage such as curling and sometimes brittle leaves. This creates poor growing conditions. If this appears to be your problem, adjust the thermostat and consider heating options such as safe space heaters or lights that provide stronger heat. In outdoor situations, it might even mean harvesting a little earlier than scheduled if the temperature is dropping faster than you anticipated.

The optimal temperature range for cannabis is between 20 and 28 Celsius.

Water

Too much water can harm your plants as well as too little water. One of the problems of overwatering is that it can wash away healthy microbes in the soil and on the plants themselves. Excess moisture can also create inviting conditions for molds, mildew and parasites. One particular parasite known as Pythium can lead to rotting of the plant’s roots and create clawing in the leaves.

Overwatering can also cause leaves and stems to be brittle or break apart during the drying and curing process. Underwatering can also lead to drooping.

Providing more attention to your watering schedule can help you figure out the best frequency. If you’re looking at your plants for clues, experts say that the plant should be dry on the surface before you schedule the next watering.

A Moisture Meter tool can measure water levels from the surface to the roots. Until you get more comfortable and knowledgeable about your particular plants, this could be a good guide.

Leaving a plant in the light too long can dry any lingering moisture but soon can lead to dryness, brittle leaves and leaves that change shape.

Some experts even suggest stopping watering for a few days as a test. This will tell you how much water your plant needs and what happens when it doesn’t get it. If your plant still looks good in a few days, it can show that you may have been watering too much. If it begins to show serious signs of distress, you can consider watering in small amounts for a few days and seeing how it responds.

Watering rate can also vary throughout the year, based on factors like temperature. A warmer day might require more water.

Genetics

Your plant’s history also plays a part. A plant that has diseases or certain weaknesses may pass them onto its descendants, so it may always have problems with a particular strain, regardless of how you try to affect the growing environment.

If you have access to the mother plant or at least her clones, it might give you an idea of how it can behave under stresses such as temperature, such as if clawing or other similar indicators show up.

Age

An older plant is more likely to have leaves begin to curl as opposed to a newer plant. But other signs, such as discoloration or changes at the tips, can indicate that age isn’t a factor, or at least the main factor.

Overall

Although it’s possible that one of the above items is causing curling or clawing, there also might be multiple causes, such as problems with temperature, moisture and fertilizer.

This makes it difficult to identify one particular cause and fix it, but could also require more experimentation and detective work once you see a plant in distress. It’s a good idea to identify these findings and start solutions early.

Letting a plant go on with curling leaves could lead to everything from a smaller yield to spreading the condition to others.

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5 Responses

  1. I have a couple of leaves that have slightly curled up tips on the sides. Is this ok or am I doing something wrong?

  2. – Hello , My boyfriend stuck my plant out in the sun this morning til about ( Its kinda cold ) &&’d Now my leaves are curling down and my top stem is purple. Its was bright and pretty this morning .. Someone please help me ..

  3. The best way to correct light burn is to move you plant away from your light source, usually between eight and 20 inches depending on the watt and lighting type. Temperatures outside of the ideal range of 70 to 80 degrees Fahrenheit also risk discoloration and curl leaves. These oddities are most common in leaves toward the top of the plant and can easily be remedied with a fan (if too hot) or root insulation (if too cold). We also recommend growing plants off a cold cement or tile floor; use a milk crate or stool to raise them off the ground when necessary.

    1. Hey do you know of a particular pest that causes the leaves to curl under where they meet with the other leaf blades on the same leaf?…kinda towards the back of the leaf. I think it’s thrips but i could be wrong. Whatever it is they’re small and to hard to see and they are hiding under where the leaves touch.

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