by Nebula Haze
The following symptoms are for when your cannabis leaves are “clawing” or curling up or curling down. Sometimes known as “The Claw”. 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!
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 a Nitrogen toxicity is curled tips (“the claw”)
A plant with a Nitrogen toxicity tends to be dark green all over
Caused by too much wind. You’ll notice that the leaves further from the fan don’t have symptoms.
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 is usually thick and muddy. Plants in poor soil will droop (often with unhappy curly leaves) no matter your watering practices.
Overwatering makes leaves fat with water, and they tend to curl down and droop
Overwatering (especially when combined with heat) can also cause leaves to curl up
This plant was grown in muddy soil, and the curling, unhealthy leaves kept getting worse and worse over time!
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.
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!
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 plant suffered from heat combined with overwatering for several days. This damaged the roots and gave it this odd leaf curling.
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.
Root rot can cause curling leaves and brown patches as well as sometimes other nutrient deficiencies
If a plant stays in the same container for too long, the roots will eventually start wrapping around the edges of the pot. This is known as being “rootbound” and causes symptoms similar to other root problems.
A rootbound plant has been in the same container for too long. Roots wrap around the edges and “choke” the plant.
Rootbound plants often droop, appear yellow, get nutrient deficiencies, and stay small. Even if you’re caring for them perfectly!
When this happens, the main solution is to transplant the plant into a bigger container. Another solution is to grow in fabric pots or air pots. These types of pots let air in from the sides, killing the circling roots (“air-pruning” them) and prevents the plant from getting rootbound for months.
To help a rootbound plant, transplant to a bigger container with fresh potting mix
Or start with air pots or fabric pots in order to prevent plants from getting rootbound at all
If plants are experiencing a lot of heat, it can make leaves droop and/or curl. Some strains can handle a lot of heat, while other strains tend to droop when it gets warm.
Heat can cause leaves to curl up
Read more about heat and growing weed:
- Cannabis Heat Stress Guide
- Air Circulation and Exhaust Tutorial
- 5 Ways to Deal with Heat While Growing Cannabis
- 3 Proven Supplements that Help with Heat Stress
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
Often a bug infestation caused general plant unhappiness, but these are some of the most likely to cause curling or clawing leaves.
Usually, you can’t see broad 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.
Hemp Russet Mites
Hemp russet mites can also cause drooping and other strange symptoms, but the bugs are so small many growers don’t realize what they’re dealing with.
Hemp russet mites cause drooping and yellow mold-like growth on the tops of plants
A closeup of the hemp russet mites
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.