Cannabis leaves curling up\upwards or downwards is something we often have while growing weed—every farmer needs to know how to fix it. Before we begin we need to understand why marijuana leaf curl occurs.

Why Cannabis Leaves that are Curling up

Overwatering

water

Overwatering is a common mistake we make, especially if we have no experience. Overwatering can put your plants at risk for bud rot and curled leaves are a major symptom of bud rot. Before watering, pay attention to your plants! If your leaves are drooping and the soil surface is dry, your plants need watering.

If your soil is moist about 1-2 inches beneath the surface then you do not need to water. Wait a little longer. Overwatering can harm plants as much as underwatering.

Underwatering can also cause leaves to curl. If your plant’s leaves spread out after watering, it means that the leaves are curled due to lack of water. 

Overnutrition 

Fertilizer is essential when growing cannabis, but young plants are too weak to tolerate excess nutrients, especially nitrogen, which can really damage your plants if given too much or put directly onto the plant. During the flowering stage, excess phosphorus and potassium can also cause leaf curl, and in severe cases, your plants can get chlorosis.

If your plants are already curling their leaves from over-fertilizing you should flush your soil. Pour clean, Reverse Osmosis water through the soil until it runs clear and your TDS meter shows a low TDS level. That said, it is hard to return your plant to the way it was before.

It is best to control the amount of fertilizer before fertilizing rather than trying to fix a problem. Start with a small amount and increase it slowly. A lack of fertilizer will be much easier to deal with than excess fertilizer.

Unsuitable Soil

There are three things to consider when choosing soil: drainage, water retention, and texture. Good soil keeps your plants in a well-oxygenated—well-textured soil that is usually black with a loose and airy texture is a great choice (basically, potting soil mixed with perlite).

Please be aware that overwatering may degrade your soil so make sure you track what you’re giving your plants. Long-term exposure to excessively humid conditions will cause the soil to become cloudy or even moldy, then your soil will be unusable, and you can only transplant your plants into good soil.

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

There are a few things you can do to make the soil drain better. Adding small pebbles or perlite to the soil will help improve aeration and make the soil more fluffy and able to drain excess water.

Genetics 

People are always crossing different strains of cannabis in hopes of getting a more potent, productive, and stable strain. Through their attempts, some genetic abnormalities sometimes occur, and curled leaves are also one of the common manifestations. If you buy some newly produced strains and experience curling leaves, you need to consider whether they have a genetic problem.

In general, this strain will be phased out quickly (unless you’re unlucky enough to get a bad batch of a normal strain). Buying a well-known and stable strain can prevent this from happening. If you’ve purchased a genetically abnormal strain and planted it, there doesn’t seem to be much you can do to stop it other than cutting off the curled leaves.

How to Fix Cannabis Leaves that are Curling up

Leaf curling can occur for many reasons, and we need to sort out the different situations before we can prescribe the right medicine. If your leaves are curling at the tips and the veins are yellowing, it may be a nitrogen deficiency, and you can increase the amount of fertilizer.

If the plant starts to curl from the stem and the tips are brown, it may be caused by overwatering, stop watering for a few days and see if it recovers. There is no set standard for how much water cannabis needs each day. Watch your plants and increase or decrease watering as appropriate until your cannabis plants look healthy and strong.

Wrap-up How to Fix Cannabis Leaves that are Curling up

As we said at the beginning, curling cannabis leaves is a very common phenomenon. If the curling doesn’t seem to be bothering your plant you’ll likely be able to fix it without having much impact on your plant’s health. This doesn’t mean you should not treat leaf curl: severe leaf curl is often accompanied by leaf burn and yellowing, which is very detrimental to the growth of cannabis.

If you have any questions, please don’t hesitate to reach out to us!

And be sure to check out our other blog posts for useful tips on becoming a great grower! 

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2 COMMENTS
  1. Hi,
    Hope you are well.
    I’m new to growing and purchased a lot of equipment.
    My plants were thriving until a few days ago when the tips of the leaves started curling up, the plants are still in vegetative stage.

    I don’t think I have been over watering them, as I have been keeping an eye on that, I have also only been feeding them 1.6 EC and PH 5.9 – 6.0

    I can also submit some images if that helps, any advice or tips would be great.

    Temperature 25 -26 °c
    Humidity ~55%

    Warm regards,
    Luke

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