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cannabis seedling leaves curling up

What Causes Curly Cannabis Leaves And How To Cure Them

There are numerous reasons why you might find curly cannabis leaves in your grow-op. This guide will explain why this phenomenon occurs, and what you can do to prevent it from ruining your final product.

Contents:

Cannabis plants can’t vocalise a call for help—but they can send signals to tell you all is not well. If you see leaves either clawing or curling, there is trouble with the trees. Don’t ignore their pleas. This blog will help you identify the causes and cures for curly cannabis leaves.

CAUSE: OVERWATERING

Overwatering will literally drown your plant’s roots. Excess water will not only rinse most of the beneficial microbes from the medium, a sodden substrate can also become colonised by algae and nasty fungi. Persistent overwatering invariably invites the parasitic Pythium, better known as root rot. Cannabis plants with droopy, claw-like leaves could be trying to tell you they are waterlogged.

“Water mould” microorganisms are just like vampires; you have to invite them in before they can do any harm. Keep them out of the garden by making sure they are not welcome. Maintaining an effective wet-dry cycle is all it takes. If you can pick up your pots, do it. Then you can tell by their weight when it’s time to water.

If you can’t lift the containers, then consider a moisture meter and make sure to carefully monitor post-watering plant behaviour. Try reducing the volume of water. Alternatively, take longer intervals between waterings. Unfortunately, Pythium is virtually incurable and will turn your plant’s roots into brown sludge. If you see droopy, curly cannabis leaves, especially with young plants, look to the roots for answers.

CAUSE: OVERFERTILISATION

A heavy-handed approach to nutrients is ill-advised. Excessive doses of nitrogen-rich vegetative growth base nutes can cause clawing in leaves. Sometimes, they will even canoe. Similarly, overdoing it with the phosphorus and potassium during flowering will cause curly cannabis leaves and scorch the tips. Chlorosis is a common symptom in both cases.

Dial in feeding. Easier said than done right? Wrong! Almost every brand of well-known cannabis fertiliser offers a feeding chart free to download from their respective websites. Granted, not all cannabis varieties will respond in the same way to fertilisers.

It’s better to start low and go slow. You can incrementally increase doses without seeing leaves curling or clawing. But if you dive right in at maximum strength, you can expect plenty of curly cannabis leaves that will probably die and eventually drop-off.
It should go without saying, but we’ll say it again for good measure; make sure the nutrient solution is the right pH. That’s about 6.0pH for soil and a more precise 5.8pH for coco/hydroponics.

CAUSE: TEMPERATURES ARE TOO HOT

Heat stress can occur indoors or outdoors. If you see curling and nasty-looking brown fringing, your cannabis leaves are sending you a distress signal. Cannabis plants can photosynthesise efficiently at moderate temperatures up to 28°C. Anything above 30°C and your plants are in the danger zone. Combine this with low RH and you’ve got real problems. New leaves will grow gnarly and old leaves will curl yellow and maybe even burn to a rusty, brown crisp.

Indoor growers must constantly maintain the optimal environmental conditions. This starts with optimal light distance. The only way to keep the plant canopy in the sweet spot is to measure and adjust until mature plants peak in height during mid-late bloom, depending on the strain. Moreover, indoor growers can utilise air-con and fans to keep the grow-op cool.

Outdoor growers confronted with heat waves and drought conditions have less control than the indoor grower. Constructing a simple screen shade will keep plants slightly cooler and may prevent leaves from fraying and curling further. You can’t really revive scorched leaves and will have to remove older foliage beyond saving. Also, planting in white pots instead of black pots will keep the root zone cooler.

CAUSE: TEMPERATURES ARE TOO COLD

Cold temperatures can cause curly cannabis leaves too. Eventually, all kinds of leaf discolouration will develop. Sure, cooler nighttime temps late in bloom can add a dash of purple charm to buds, but prolonged exposure to temperatures below 10°C will kill your plants. Flowers will be loose and leafy if plants even make it to harvest. Coupled with high RH, buds will be moist and become vulnerable to Botrytis, AKA bud rot.

Indoors, if temps are too low, you can always add more grow lights and turn a negative into a positive. Outdoor growers might consider an early harvest, or if possible, moving plants indoors at night. Cannabis is a hardy plant species, but outside of the optimal 20–28°C temperature range, leaves will curl or claw.

A FINAL WORD ON CURLY CANNABIS LEAVES: GENETICS

Genetics are the cause of all kinds of cannabis leaf deformities and mutations. Some strains occasionally have a tendency towards curly leaves or other odd traits. Most growers will thin out these plants. All the shrewd cultivator can do is write it off as bad luck.

Sativa strains and many autoflowering varieties are sensitive to high doses of fertilisers. This is a trait that can cause problems for beginner growers. The solution is to research your reefer. Always find out as much as you can about the genetics of a strain before you decide to grow it. Curly cannabis leaves can be completely avoided if you know how to keep your plants healthy.

Cannabis leaves curling or clawing are signs your plants are suffering. Something is going wrong in the garden. This blog will help you save the stash.

Seedling Leaves Curling Up

Shanus
Active Member

I know this has been covered millions of times, but i didnt find any pertaining to seedlings only about 10 days old. Here’s the short setup

1 part perlite
3 part peat moss
1 part vermiculite

Soil ph steady at 6.7 Watered with tap water buffered to 6.0 w/sulfuric acid (perhaps this is issue, first grow using s/a as ph lowering?)

1000w mh bulb was at 8″ above plants, now at 24″ above plants. Cooled hood, no heat issues. Good air circulation, not direct at plants.

Humidity always 40-50% day temp 78deg, night 72deg

My last grow was with a 400w hps and I didnt have this issue. Anyone seen this before? All seedling are feminine white widow and Himilayan gold. Since they show this curl regardless of genetics, I’m gna rule that out. All seedlings treated the same since birth.

Thanks in advance for any ideas. I’m hoping this thread may help me and many others

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bizzarebud
Well-Known Member
BEEFY
New Member
pinkjackyle
Well-Known Member
Shanus
Active Member

Thanks for the replies so soon. Im new to the 1000w club, but so happy ive got too much light. for anything. Im using this potting mix until i repot into 3gal w/1 part perlite and 1 part verm. Im still so confused about the earth juice i got, Im not sure how to ph it.

I had read NOT to give nutes in the first 2 weeks, but mayhaps they are already gna need some? Im doubting this is a nutrient issue..yet. They are soo young. If the light kicked their ass, are they gna bounce back now that I’ve moved it up? Man I hope so, I was hoping for a 3×3 (9) plants, and am so running out of seeds. Im staring in on ’em every 4hrs or so, so I’ll keep close tabs on it. For now, the light has been raised to 24″ for the last 36hrs, let’s hope that bounces em back. Any chance this is from over watering? Thanks again

BEEFY
New Member

Thanks for the replies so soon. Im new to the 1000w club, but so happy ive got too much light. for anything. Im using this potting mix until i repot into 3gal w/1 part perlite and 1 part verm. Im still so confused about the earth juice i got, Im not sure how to ph it.

I had read NOT to give nutes in the first 2 weeks, but mayhaps they are already gna need some? Im doubting this is a nutrient issue..yet. They are soo young. If the light kicked their ass, are they gna bounce back now that I’ve moved it up? Man I hope so, I was hoping for a 3×3 (9) plants, and am so running out of seeds. Im staring in on ’em every 4hrs or so, so I’ll keep close tabs on it. For now, the light has been raised to 24″ for the last 36hrs, let’s hope that bounces em back. Any chance this is from over watering? Thanks again

Shanus
Active Member

Well, Ive since watered my babies with 1/2 strength earth juice grow and a touch of bloom. I repotted them in perlite/verm mix and they took the transpant well it seems. Tiniest drooping, but success i think. I know the roots aren’t logged in water, and the lights have been at 32-36″ above plants for about a week now, yet all the leaves are still curling? WTF! My temps and humid are always spot on, and even the new leaf growth shows signs of curl from the get go.

Im now out of seeds for the space I’ve alotted, so off to spend another 75$ to try 10 more beans. How aggravating, all the best plans in the world and BOOM, time to regroup. Anyone have any ideas? Thanks

I know this has been covered millions of times, but i didnt find any pertaining to seedlings only about 10 days old. Here's the short setup 1 part perlite… ]]>