Cannabis Leaves Curling Up or Down (Causes and Solutions)

Table Of Content

• 1. Why are My Cannabis Leaves Curling up?
• 1.1 Too Strong/Too Much Direct Light
• 1.2 Dry Environment
• 1.3 Overwatering
• 1.4 Over Fertilization
• 1.5 Pests
• 2. Why are My Leaf Tips Curling Down?

Why are My Cannabis Leaves Curling up?

There are a few different types of leaf curl. As the images shown above, you may notice the sides of the leaves curling upward. This may be referred to as “canoeing” or “tacoing”, as the side of the leaves curl up and makes the shape of a canoe, or taco! You may also notice the leaf tips curling upward and pointing toward the light. These two types of leaf curl can be attributed to some type of stress on the cannabis plant.

1. Too Strong/Too Much Direct Light

Most commonly, the symptom is a result of improper intensity of your cannabis grow lights. Too strong of light, or too much direct light will cause the leaves to curl up.

This is fairly easy to fix! You can either lower the light intensity, or strength. When growing cannabis at home with double-ended or HPS light fixtures, source of the problem will most commonly be the light intensity. Most HPS and double-ended fixtures operate at 1000w, hence if you lower the intensity by 30%, it should get rid of the issue of cannabis leaves curling up!

You may also have to increase the space between the canopy and the actual light fixture. This is a more common remedy when growing under LED lighting, as most LED fixtures allow you to grow with minimal space between the canopy and light. However this can lead to too much direct light for the plant, and may be the cause of the leaf curl. The plant would be better suited with a bit more space between the light and canopy!

2. Dry Environment

Image via Spider Farmer Official

Another culprit to consider when you notice the cannabis leaves curling up, is the environment. Often times growers think that they need to have a drier grow space to mitigate mold on weed and fungal issues. When the environment becomes too dry, the plant tissue gets moisture wicked away, and causes the leaves to shrivel and curl.

This often works in conjunction with temperature. If the grow areas is too hot (above 86 °F/30 °C), or too cold (under 55 °F/12.78 °C) the plant is unable to transpire and move water throughout the plant. This also causes a wicking of moisture from the plant tissue and will cause the leaves to shrivel, twist, or curl up! If you're growing with Hey abby hydroponic grow systems, keep an eye on these parameters from your smartphones from time to time, to make sure she's safe and sound in there.

If it is a temperature issue, you may also notice a discoloration of the leaves, as they will turn pale or yellow a bit with improper environmental temperatures. Try to keep the moisture around 40%-65% (depending on the stage of growth), and the temperatures between 70-84 °F (21-29 °C). These parameters will help avoid any upward leaf curling that may occur.

3. Overwatering

Root rot: brown, slimey root

Speaking of transpiring, overwatering can also cause the cannabis leaves to curl up! Roots need oxygen to operate and survive. If they receive too much water the roots will drown, and they will not able to move water through the plant. Water is the delivery method for the plants nutrition, if there is too much water present, the roots will shut down and the plant is not able to receive the nutrients it needs!

If the plant is so overwatered that oxygen becomes depleted, you may start to get something called “pythium” or root rot! This can be a death sentence for cannabis, so it is crucial to make sure you’re not drowning out the roots.

When hand watering, you will want to give the plant water until you notice runoff from the pot. Once runoff is reached, the media has been fully saturated, and flushed and nutrient buildup may occur in the media.

When the plant receives too much water, it may also cause the plant to transpire too much, and can cause moisture to sit on the leaves in some areas. When moisture sits on the leaves, the light hits the moisture and is magnified! This can cause burning and curling of cannabis leaves as well.

4. Over Fertilization

Transversely, over fertilization can also cause issue with the plants leaves! You need to think of the roots like a straw, when the cannabis fertilizers are mixed in at the proper strength, the roots are able to transport nutrients throughout the plant via the water that transpired throughout. However, when the nutrients solution is too strong, minerals will clog the roots system, making them unable to uptake and transport water.

This will not only cause the plant to dry out, but can also cause a nutrient toxicity. If the plant receives too much nitrogen, phosphorus, or potassium, it can also cause twisting or curling up of the plants leaves! It’s always best to give the plant a balanced nutrition and water regimen.

A lot of growers think that “more is better” but that is rarely the case when growing cannabis. The cannabis plant prefers and thrives with a balanced diet, and water supply. An easy and reliable method to prevent over-fertilization is feeding them with Hey abby's premium pre-mixed nutrients, which features a perfect balance of NPK and well suits every growth stage of cannabis.

5. Pests

Pests causing cannabis leaves to curl up

“Save the best for last” well, not quite! The final reason the plant leaves curl up may be due to pressure from pests, specially in large numbers.

Bugs and pests, like spider mites, russet mites, aphids, and broad mites typically live on the host plant, on the underside of leaves. Often times they will lay eggs and feed on the tissue of the plant. This can cause damage to the leaves, and eventual dying of the leaf if not treated properly.

The plant also may respond by sending more water and nutrients to this section of the plant, and as mentioned previously; if the plant is receiving too much water and/or nutrients, it can cause the leaf tissue to burn, dry and curl!

In addition to curing there are some other things to look for to determine if pests are causing the cannabis leaves curling up. When broad mites feed on cannabis plant, they will often cause the leaves to twist and take on a very shiny look. When other mite species feed on the plant, you will notice small yellow spotting on the topsides of the leaves, and even brown and dying leaf matter.

Why are My Leaf Tips Curling Down?

While leaf tips curling up is a clear sign of stress on the plant, it is less common than having the leaf tips curls downward. This is known as “clawing”, as the leaves blades pointing downward resembles a claw! The downwards leaf tip is also a sign of stress, but commonly much lighter stress than those of the upward leaf curling.

Some causes may be that the environment is too warm, which will dry out the media and the plant will not have enough access to water. Another possible consideration is the humidity of the grow space: similar to upward pointing leaf tips, if there isn’t enough humidity in the environment, the plant will wilt and you will notice the leaves droop and point down.

So make sure your grow area stays under 86 °F/ 30 °C, and has a comfortable level of humidity (between 40%-65% depending on the stage of growth). Make sure that you’re watering and feeding your plant enough so that the medium doesn’t dry out and cause root damage.

Root damage may also be the culprit to leaf tips pointing downward! If the roots are not receiving enough oxygen, or water, they will not be able to move water through the plant and you will be able to see it in the leaves! Again, balance is key when growing cannabis! Make sure you’re giving your plants enough water so they don’t dry out, but not too much to the point of depleting root function!

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