Are your marijuana plants starting to look like they're straight out of a horror movie? Cannabis leaves curling down may resemble witches' hands—but what happens when you don't identify and fix the problem is truly terrifying.
Also known as clawing, due to the signature claw-like shape, cannabis leaves curling up or down signal several conditions requiring your immediate attention. Read on as we unpack the possible reasons and how to prevent and fix them.
What is leaf curling?
Curling leaves are a common problem cultivators face when growing cannabis seeds in various growth stages. It causes leaves to take a claw shape and can sometimes occur with other abnormalities like yellowing or browning.
When you spot leaves twisting and curling on your marijuana plants, determine what's causing it and treat it as soon as possible. If left untreated, your flora may experience stunted growth, necrosis, or even death.
Reasons why your cannabis leaves curl up and down
There are various reasons why cannabis leaves spiral up and down, some more serious than others. The direction they turn is crucial in determining the source of the clawing. For instance, heat stress causes cannabis leaves curling up, but a pest infestation triggers downward curves.
Some other reasons for marijuana leaves curling down include:
- Root rot
- Thick and muddy soil
- Windburn
- Unstable climate
- Over-fertilizing
Keep reading as we delve deeper into why your cannabis leaves are curling down or up.
What causes curling cannabis leaves?
Marijuana leaves curling isn’t an isolated problem but one of the symptoms of the cause. To stop the foliage from looking like ramen noodles, you need to get to the root of the issue.
Here are possible complications and the signs to look out for so you can make the correct diagnosis and straighten things out:
Overwatering or underwatering
Water is the source of life, but you can have too much of a good thing. Signs of overwatering cannabis include leaves curling down, yellowing foliage, and all-around wilting.
The primary concern with overwatering is that the dampness summons Pythium. Growers cower away from this parasitic condition that's attracted to water-soaked mediums. It causes root rot and begins killing plants through necrosis within 1–2 weeks of arrival.
Here are the signs to look out for if you suspect the weed leaves curling down are due to overwatering:
- Drooping plants soon after watering (typically within a few hours or overnight)
- Leaves are firm to the touch but curl inwards from the stem to the tip
- Marijuana leaves curling down and not up
- Weak stalk base and brown mushy bits at roots (signs of late-stage Pythium infection: act fast)
- Fat leaves
If overwatering occurs with heat stress, you notice the cannabis leaves are curling up instead of down.
Underwatering is also a common reason for marijuana leaves curling down. It has all the same symptoms as overwatering, except the leaves aren't fat or firm to the touch; they're usually frail. If you water the plants and they perk up, underwatering is the cause.
Nitrogen toxicity
Nitrogen is one of the most essential nutrients for cannabis, and one of the leading causes of marijuana leaves curling down. This macronutrient plays a role in developing new growth, photosynthesis, and reproduction. High amounts of nitrogen typically show up later, resulting in leaves curling down during flowering. A nitrogen deficiency causes yellowing leaves and necrosis, whereas an excess of Nitrogen creates the classic claw with leaves completely turned inwards.
Most growers make the mistake of topping with nutrient blends and using a high nitrogen fertilizer. It overwhelms the plants' system, causes rapid growth, and then slowly curls leaves, affecting harvest quality. Here are the signs to look out for when you think marijuana leaves curling is due to toxic nitrogen levels:
- Super pigmented green foliage
- Brown or yellow spots on leaves
- Plant stress
- Nutrient burn
- Clawed leaves
Age
All plants have life expectancies, and as marijuana flora matures, their older leaves show signs of aging before they die. Cannabis leaves curling down are perfectly normal features in elderly plants. If you see cannabis leaves curling up instead of inwards towards each other, it's not an age-related issue. Another sign that clawing isn't due to aging is that all leaves are crimping on the plant rather than just the older ones.
Cannabis plants are annuals, so they flourish and bear fruit for one season, you collect their buds, and they die. Growers can use re-vegging techniques to get a second harvest, but this is tricky even for experienced cultivators. Marijuana leaves curling down are just one of the signs of aging; other things to look out for include:
- Smaller yields
- Plants get stressed out easily
- Wilting or shrinking.
Moisture Content
Keeping your plants hydrated prevents them from becoming Crispy Fried Cannabis—aka CFC. Since they get 12–24 hours of light in different stages, they become dry and brittle without adequate moisture. Insufficient hydration and exposure to high-intensity light, especially from growing weed indoors, results in cannabis leaves curling down or up if there's heat stress. Potential causes are underwatering, low humidity levels, or excessive light.
Here are some signs marijuana leaves curling is due to low moisture content:
- Leaves feel super dry and have the texture of potato crisps
- Brown or yellow tips
Genetics
Unhealthy parent plants create sickly seedlings. If you buy marijuana seeds with poor genetics, it could be the reason.
Of course, some strains grow naturally curly leaves, but most respectable cultivars develop them to improve these genetic abnormalities. You get expert-level and beginner cannabis seeds with stabilized genetics and consistent results when you buy from our reputable store
Some of the red flags that cannabis leaves curling on your plants are due to unstable genetics include:
- Seedlings become easily infected, even with optimal conditions.
- Plants need extra care than usual and often go into stress.
- Low or unsatisfactory harvests, even with a high-yielding strain.
Incorrect temperatures
It's common knowledge that marijuana plants prefer hot temperatures, but that doesn't mean they all tolerate scorching conditions. Heat burn is easy to identify because it causes cannabis leaves curling up instead of down and brittle foliage.
Cold temperatures can be just as dangerous. Some strains handle cooler conditions like those from Northern Lights feminized seeds, so pick these cultivars if you live in a cold climate. Heat stress causes fragile, crispy leaves, and prolonged cold causes necrosis and stagnant growth. Both conditions lead to cannabis leaves curling.
Pest or bug infestation
It's scary to think your plant babies are infected with pests, but it's common. Bugs or pests live inside the marijuana plant for a while, unnoticed. You can't see them, but it’s easy to spot the damage they cause. As they eat away at the foliage, you can identify cannabis pests when there are leaves curling down. Aphids and mites are common troublemakers that drain the nutrients from each leaf. If left untreated, plants experience deficiencies and severe necrosis and eventually starve to death.
Here are signs that leaves twisting and curling are due to pests or bugs:
- Weird spiraling in different directions
- Dry foliage or sometimes wet-looking leaves that are crisp to the touch
- Yellow, mold-like growth towards the top of the plants
- Dark brown spots on leaves
Too much fertilizer
Fertilizer helps cannabis flora grow strong branches and roots, but overfertilization is detrimental to their health. The high levels of vitamins like nitrogen and phosphorus found in plant food may cause nutrient overdose and lockout. Be wary if marijuana leaves are curling down in a young plant. It's best to avoid fertilizer on seedlings and early vegging flora because they lack the robust defense system and filtration that comes with maturity.
Similar to toxic nitrogen levels, one of the critical signs of overfertilization is leaves twisting and curling. Here are some other red flags to look out for:
- Leaves with scorched, dark brown tips
- Yellow or brown hues present on the back and edges of the leaves
- A yellow halo in the middle of the leaves separates the healthy center from the burnt edges
- Entire leaves turn yellow or white (late-stage chlorosis; act fast).
Wind Burn
Have you ever had the wind mess up your hairdo? Marijuana plants go through it too. If you notice your cannabis leaves curling down, it could be because of excessive wind. Here are some signs that point to wind burn:
- Burnt leaf edges, especially where the wind hits the most
- Central foliage of the plant is green, and the outer leaves are yellow
- Sickly or stunted plants
- Spots that look like burn marks on leaves
The primary signal marijuana leaves curling is due to this condition if your plants are in a windy area. Indoors the fans may be too powerful or too close to them. Outdoors the climate could be too breezy. The solution is as simple as moving the fans or relocating the plants.
Light Burn
You might enjoy getting a tan, but your cannabis plant doesn’t. Excessive sunlight or bulbs with high wattage burn the foliage and cause symptoms like marijuana leaves curling down. Prolonged intense light exposure causes severe damage to weed plants, but you can prevent it if you spot the signs early. Here are some symptoms of light burn:
- Leaves closer to the lamps or sun (usually the ones at the top) are yellow or burnt
- Yellow leaves while the veins are still vibrant green
- Leaves are yellow but don't pluck off or fall easily like nitrogen or nutrient burn
Things you can do to reduce and stop leaf curling
The excellent news is most of the causes of marijuana leaves curling are fixable if treated early. Here are our tips to stop your leaves from spiraling out of control:
Lower nitrogen
Excessive nitrogen levels result in marijuana leaves curling down. Once the amounts are high, it's challenging to remove this nutrient. As a general rule, avoid chemical fertilizers and nutrients as they lead to oversaturation if misused. Here are some tips to reduce high nitrogen levels and prevent cannabis leaves from curling:
- Flush and renourish the soil with organic fertilizers.
- Incorporate wood chips or sawdust in the medium to lower the bioavailability of nitrogen in plants.
- Use organic nutrient sources like coffee grounds.
Fertilize correctly
If the nutrient burn or deficiencies are the reason for leaves twisting and curling in your cannabis plants, act fast. Flush the soil if your greenery shows signs of nutrient burn and use organic fertilizer when renourishing the soil. If marijuana leaves are curling down because of fertilization problems, you need to take action before it leads to nutrient lockout and affects buds.
Don't overwater or underwater
Water is essential for helping plants grow and promoting better circulation of vitamins. On average, cannabis plants need around 36 inches of water daily, depending on the strain. To prevent marijuana leaves from curling up because of overwatering and heat stress or spiraling down from underwatering, follow these tips:
- Water till you reach 25–33% of the pot’s capacity.
- Allow the first inch of soil to be moist but not soaked.
- Start watering close to the stem and work your way towards the edge of the pot.
Frequently asked questions about cannabis leaves curling
Why are the edges of my leaves curling up?
Cannabis leaves curling up is a vital sign of heat stress. Other conditions like infestations or a nitrogen overdose cause leaves to curve downwards, but scorching temperatures make leaves turn upwards. If your plants are overwatered and growing through extremely hot temperatures, their leaves feel thick and turn upwards.
Why are cannabis leaves curling up and down till browning?
If you're dealing with cannabis leaves curling up and down, and they start to brown, it could be due to a lack of moisture. It may also be because of heat stress or burn if the leaves curl upwards. You need to ensure the soil is hydrated, lower the intensity of lights, and spray leaves with cool water.
Cannabis leaves curling up and down during flowering?
When you spot marijuana leaves curling down during flowering, it's most likely a sign of nitrogen overload. Other red flags include abnormally green foliage and adverse reactions like plant stress manifesting in the latter stages. Flush the soil and reset it with organic nutrients.
Marijuana leaves curling up aren't a beauty statement: Take action
There are many reasons cannabis leaves are curling down or up, like nitrogen overload, unstable climate, and overwatering. It's a common issue, but it doesn’t affect your crops if you act early. Using the tips we provided, nurse your plants back to health in no time. Curling cannabis is avoidable if you choose a strain that works for your climate and comes from healthy parents. One of the main contributors to leaves twisting and curling is poor genetics. Ensure you buy cannabis seeds from our reputable store. Shop our wide range of products with stabilized genetics and get consistent results. Get your seeds today.
