Cannabis Leaves Curling Up? Causes and How to Fix it

Cannabis leaves curling up? We often encounter cannabis leaves curling up or downwards while growing weed. Farmers need to know how to fix this problem. The reason why marijuana leaves curl is important to understand before we proceed.

Main Reasons Why Cannabis Leaves that are Curling up


Overwatering is a common mistake, especially for inexperienced gardeners. Plants that are overwatered are more likely to get bud rot, which is characterized by curled leaves. 

Before watering, pay attention to your plants! If your leaves are drooping and the soil surface is dry, your plants need watering.

Water is not necessary if your soil is moist about 1-2 inches below the surface. Let’s wait a little longer. Underwatering and overwatering can both harm plants.

Curled leaves can also be caused by underwatering. When your plant’s leaves spread out after watering, the leaves are curled due to a lack of water. It is possible to restore them to a healthy state by watering them frequently.

Overnutrition – Reasons Why Cannabis Leaves that are Curling up

Growing cannabis requires fertilizer, but young plants cannot handle excess nutrients. It includes nitrogen, which can damage your plants if given in excess or sprayed directly on them. 

In severe cases, excess phosphorus and potassium can cause chlorosis during the flowering stage. You should flush your soil if your plants are already curling their leaves from overfertilizing. 

You should pour clean, Reverse Osmosis water through the soil until it runs clear and your TDS meter shows a low level of TDS. Nevertheless, it is difficult to restore your plant to its former glory.

Instead of trying to fix a problem, control the amount of fertilizer before fertilizing. Make slow, gradual increases to your donation. A lack of fertilizer will be much easier to deal with than excess fertilizer.

Unsuitable Soil

The three factors to consider when choosing soil are drainage, water retention, and texture. A well-textured soil with a loose, airy texture (basically, potting soil mixed with perlite) will keep your plants well-oxygenated.

Overwatering can degrade your soil, so keep track of what you’re giving your plants. Excessively humid conditions will cause the soil to become cloudy or even moldy, and you will have to transplant your plants into fresh soil.

Another viable option for soil is coco coir, but it requires more maintenance because it is more porous than traditional potting soil.

Several things can be done to improve soil drainage. Adding small pebbles or perlite to the soil will improve aeration and make it more fluffy and water-draining.

Genetics – Reasons for Cannabis Leaves that are curling up

It is common practice to cross different strains of cannabis in order to get a more potent, productive, and stable variety. Curled leaves are one of the most common manifestations of genetic abnormalities caused by these attempts. 

If you buy some newly produced strains and notice curling leaves, you should consider whether they have a genetic problem.

This strain will generally be phased out quickly (unless you get a bad batch of a normal strain). This can be prevented by buying a well-known and stable strain. 

Other than cutting off the curled leaves, there doesn’t seem to be much you can do to stop a genetically abnormal strain from growing.

How to Fix Curled Cannabis Leaves

Before we can prescribe the right medicine, we need to determine the cause of leaf curling. There may be a nitrogen deficiency if your leaves are curling at the tips and the veins are yellowing, and you can increase the fertilizer application.

It may be caused by overwatering if the plant curls from the stem and the tips are brown. Stop watering for a few days and see if it recovers. Cannabis does not have a set standard for how much water it needs each day. 

Make sure your cannabis plants are healthy and strong by increasing or decreasing watering as needed.

Over Fertilization

Too much of a good thing can quickly become a bad thing. This is true when you’re feeding your cannabis plants, too, as too much fertilization causes a condition known as nutrient burn. 

There are a handful of different nutrients that are capable of causing such issues in your cannabis leaves. The three most notorious are nitrogen, phosphorus, and potassium.

When too much fertilizer is given to your cannabis plants, you’ll notice leaf curling first. Depending on the severity of the overfeeding, you may see entire fan leaves clawing and some turning into small canoes. 

Others will have burnt, brown tips, similar to what you see in heat stress. Unfortunately, fertilizer is necessary to get the most out of your harvest. 

As such, you’ll probably deal with curling from over-fertilization at least once while growing your plants.

Curing Over Fertilization

To fix over-fertilization issues, you have to get your fertilizer amounts just right. Once you start to notice curling in your leaves, you’ll have to start over. Rinse your cannabis plant’s roots with fresh water. 

This will help remove any excess fertilizer. Then, start the feeding process from scratch. Be sure to follow the manufacturer’s recommendations.

If the problem persists, your only real option is to reduce the amount of recommended feed or find another fertilizer. 

Just remember, always start with less if you’re concerned about overfeeding. It’s easier to increase nutrients than it is to reduce them.


Why are my leaves curling down?

When leaves curl or ‘cup’ at the tips and the margins, the plant is trying to retain moisture. Any form of downwards curling usually indicates overwatering or overfeeding.

Why are my leaf tips curling up?

CAUSE: Heat stress causes rapid evaporation, so plants curl up to conserve moisture. Plants too close to high-intensity lights are prone to heat stress, but it can be a problem in any room where temperatures are persistently above 80 degrees F.

QUICK FIX: Set up fans to blow out hot air and bring in the cooler fresh air.

Can you reverse leaf curl?

Transplant shock, root damage, and pruning are other causes of leaf curl. Leaves will thicken and curl up, but remain green. With proper care, the plant usually recovers and the leaves will go back to normal.

How do you treat leaf curls?

Leaf curl can usually be controlled satisfactorily by a spray of a suitable registered fungicide at any stage of dormancy. Most effective control is achieved by spraying when the buds are swelling but before they have opened. It’s not possible to control the fungus once it’s entered the leaf.

Wrap-up How to Fix Curled-Up Cannabis Leaves

Cannabis leaves curling is a very common phenomenon, as we said at the beginning. If the curling doesn’t seem to be bothering your plant, you can probably fix it without affecting its health much.

However, you should still treat leaf curl: severe leaf curl can cause leaf burn and yellowing, which are detrimental to cannabis growth.

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