September 10, 2020

Why Are My Cannabis Leaves Curling Up + How To Fix It!

Are your cannabis leaves curling up and not looking great? Unfortunately this is often a problem faced when growing cannabis. Often referred to as “The Claw” because of the bunched up look of the leaves, its a common but totally fixable issue when growing cannabis!

The unfortunate part about curling cannabis leaves is that there are actually quite a few different issues which could be causing the issue, which makes it hard to diagnose what the actual root of the issue is.

Thankfully below we’ll cover some of the most common causes of curling or clawing cannabis leaves, and what you can do to correct them!

How to Fix Curling Cannabis Leaves?:

Just like any plant, when cannabis plants are dealing with stressors that they can’t handle, they begin to hurt. With cannabis this hurt shows by when the leaves start to curl up or down.

If you notice your leaves starting to curl either up or down, then that means your plants are in trouble!

marijuana leaves curling

The only way to fully fix the curling leaves is to identify what the specific issue is, and then correct this issue and let your plant begin the healing process. Obviously your plant can’t talk to you, so it can be difficult to identify what the actual issue can be, but thankfully we’ve done our research and identified a few of the most common causes.

Over Watering or Under Watering Your Cannabis Plants:

One of the most common causes of cannabis leaves curling is due to over watering your plants. Over watering or under watering your plants cause many issues in growth by essentially drowning your plant and wiping away valuable nutrients from the soil, or not providing it with enough water to perform growth functions. Watering cannabis plants is all about finding the sweet spot between over and under watering.

weed leaves curling up

If you notice curling or dropping leaves, this is a big indicator of over watering. If you notice wilting or the leaves looking very weak and frail, this is a big sign of under watering.

A good eye of thumb is to make sure the top layer of your soil feels dry before you water it again. I generally recommend sticking your index finger in the soil up to your first knuckle and see if you feel water. If you don’t, it’s time to water again.

Heat Stress and Cannabis Plants:

Heat stress is another issue that will undoubtedly lead to the curling of your marijuana leaves. This predominately happens when growing outdoors, but can also happen if grow lights are too close to the plants or at a too high off wattage (providing too much heat).

Furthermore, if you’re growing indoors or growing in a closet, then you definitely need some air circulation to ensure that the air is moving and cool.

Cold Stress:

Similar to heat stress, curling can also happen if the plant gets too cold. Generally, cannabis is grown in pretty warm and humid environments, so only use cool temperatures if you have strains that are designed for cold weather like our New England Strains. You can also see low humidity leaf curl if your humidity levels are too low.

If your grow is too cold, I’d suggest adding additional grow lights to ensure that the plants are receiving the warmth that they need.

Soil Deficiencies:

The next most popular reason that you might see curling is due to the nutrients in the soil. If you’re using a standard nutrient-rich garden soil, then you shouldn’t have this issue, but if you do, you might need to switch brands.

Cannabis requires specific nutrients to grow efficiently in each of its life stages, and if they don’t have these nutrients then they will begin to curl and sometimes wilt.

One of the main deficiencies that causes this is magnesium deficiency.

If you begin to notice that leaves are turning yellow and drying out or becoming crunchy then my first guess would be magnesium deficiency. Take particular notice to the oldest flowers, because they will be the first affected since they’re the oldest.

Thankfully, just by testing some more nutrient rich soil, you can often times turn this around and have your cannabis react much more positively to new soil. That being said, if you switch soil make sure you’re watching it for the next few weeks because it can take a few days for you to see any benefit.

Using Grow Lights To Prevent Curl:

If you are growing your plants inside, then obviously you’ll need some sort of lighting to trigger the flowering stage and begin the growth of your cannabis. That being said, if you aren’t using the right type of grow lights then you can quite easily see your leaves start to droop and curl.

This often means that your plants aren’t getting the lighting and “sun” that they need to grow. If you’re seeing droops that usually will mean that your current grow lights aren’t strong enough and not providing enough light to your plants.

That being said, if you are seeing your plant brown or get super dry, that could mean that your grow lights are too powerful or too close to your plants which would mean they are getting burnt, often referred to as light burn.

Why Do Cannabis Leaves Curl?

So above we talked about a few reasons which can cause weed leaves to curl, but why do they physically curl?

Generally when leaves begin to curl it means that the leaf is weak and it loses its structure based on the weak cells of the leaf. For example, this happens with over watering and under watering because the leaf doesn’t have the ability to grow properly, and it causes loss of structure, which causes the leaves to fold and grow in irregular shapes.

Final Thoughts on Curling Leaves:

Curling weed leaves can be a really frustrating thing to deal with because there are so many different causes. That being said, by being informed on a few of the different causes, you should be able to identify which issue is affecting your grow. Once you’ve identified the issue, generally you still have time to turn it around and save your crops!

Related Posts

3 Cannabis Low Humidity Leaf Curl Fixes

Spider Mites On Buds At Time Of Harvest – What To Do!

Why Does My Cannabis Smell Like Hay/Grass

How To Use Rapid Rooters Plugs To Germinate Cannabis Seeds


Jacob is the owner and lead author here at  He's been involved in the cannabis growing industry since 2012.  Based outside of Denver, Colorado, his passion involves sharing his knowledge of growing and the cannabis industry.

Jacob Hydra

Leave a Reply

Your email address will not be published. Required fields are marked

{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}