What causes upward leaf curl?

It can be a number of things. Here's a guide hope it helps. GrowWeedEasy Fix Curling or Clawing Cannabis Leaves by Nebula Haze The following symptoms are for when your cannabis leaves are “clawing” or curling up or curling down. I’ll give a short explanation with pictures of each problem, plus links to the solutions! Fix this common (but hard to diagnose) marijuana problem today! Nitrogen Toxicity A Nitrogen toxicity is the result of the plant getting too much Nitrogen (usually from too high levels of nutrients overall, or by using a Vegetative nutrient in the flowering stage). It causes dark green leaves and curled tips (“the claw”). One of the main symptoms of an Nitrogen toxicity is curled tips (“the claw”) This marijuana plants has been fed too much nitrogen Image A plant with a Nitrogen toxicity tends to be dark green all over A Nitrogen toxicity can also cause certain leaves to turn yellow, but other than that it looks nothing like a cannabis nitrogen deficiency​ Learn more about a cannabis Nitrogen Toxicity Wind Burn Caused by too much wind. You’ll notice that the leaves further from the fan don’t have symptoms. These clawed leaves were wind-burned Example of cannabis wind burn - the leaves are twisted and pointing up Learn more about cannabis wind burn Bad Soil / Overwatering / Underwatering You can help prevent over and under-watering your cannabis plants by always starting with good soil or coco coir. Bad Soil When soil is thick and muddy, plants will be droopy (often with unhappy curly leaves) no matter your watering practices. This seedling started "damping off" (dying) due to terrible soil Overwatering Overwatering makes leaves fat with water, and they tend to curl down and droop Overwatered marijuana plant - pot is too big Overwatering (especially when combined with heat) can also cause leaves to curl up This marijuana plant was overwatered for over a week, causing these odd symptoms in addition to persistent droopiness This plant was grown in muddy soil, and the curling, unhealthy leaves kept getting worse and worse over time! Example of curling, clawing leaves caused primarily by overwatering​ Underwatering Underwatering causes symptoms that often look like overwatering, but you’ll know it’s underwatering if the plants perk up each time after you water them. Under-watered cannabis seedling Root Problems Although often caused by overwatering, once the roots are sick you’ll see symptoms for a little while even after you start watering your plants properly. Unhealthy roots can cause all sorts of problems including curling and clawing! Unhealthy Roots in Soil/Coco This plant’s roots were damaged from being overwatered and too hot for several days. As a result the leaves took on a strange, blistery appearance. This seedling has cupping leaves due to marijuana root problems This plant suffered from heat combined with overwatering for several days. This damaged the roots and gave it this odd leaf curling. This odd cannabis leaf curling was caused by a combination of heat, overwatering, and incorrect root pH Root Rot Root rot is something marijuana hydroponic growers can suffer from if pathogens attack the roots. It is often triggered by heat and/or lack of bubbles near the roots. Example of the clawing, curling leaves caused by cannabis root rot (root problems) Root rot can cause curling leaves and brown patches as well as sometimes other nutrient deficiencies The burnt discolored leaves of a cannabis plant with root rot Light Burn Plants can get light burn (sort of like a sunburn) even if the temperature is completely under control. The symptoms are usually concentrated close to the grow lights. Sometimes this can cause leaves to claw and curl downwards. Light burn can cause the leaves closest to the light to turn yellow Cannabis suffering from light stress Learn more about light burn Bugs & Pests Often a bug infestation caused general plant unhappiness, but these are some of the most likely to cause curling or clawing leaves. Broad or Russet Mites Usually you can’t see broad or russet mites because they live inside the plant. The main symptom of an infestation is strange leaf curling that is specific to this pest, as well as “wet” looking leaves. The top of this marijuana plant is droopy because it's been attacked by broad or russet mites. You can see the edges of the leaves are starting to get glossy Example of twisted new growth caused by cannabis broad mites Fungus Gnats Fungus gnats look like tiny flies buzzing around your topsoil. Although a few fungus gnats won’t really hurt your plants, a big infestation can damage the roots, causing symptoms similar to other types of root problems. Fungus gnat damage on a flowering cannabis plant Learn about other types of bugs and pests that can attack your cannabis plants! Jump to… 7 Step Fix to 99% of Cannabis Growing Problems Pictures of Marijuana Plant Problems What does pH have to do with nutrient deficiencies? 10-Step Quick Start Guide to Growing follow us on instagram Was this article helpful? 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