The last thing growers want to see is their cannabis leaves curling up or canoeing down. While this problem can be the result of various factors, the fact cannabis plants themselves are over 90% water is usually telling.
There are several other potential answers to the question; “Why are my cannabis leaves curling?” Read on to know how to make an accurate prognosis and quickly cure your plant’s affliction.
Cannabis leaves curling up: 5 main causes
Either over-watering or under-watering your crop is the most likely reason for curling weed leaves. Don’t immediately jump to conclusions though, because some old weed leaves curl naturally. If the entire plant is affected, you need to take immediate action.
The most common reason for twisting cannabis leaves is overwatering. Watering your cannabis crop is vital for survival, but overdoing it can drown the roots and snuff out your homegrown dreams.
Twisted cannabis leaves soon become droopy. It will only get worse if growers don’t address the root of the cause.
Roots need oxygen, and if they’re waterlogged, they could suffocate. The water delivers nutrients to healthy plants through the roots. This process is impossible in very wet soil, so plants start to wilt with weed leaves curling up.
Continued overwatering can lead to Pythium, aka root rot, a parasitic condition that may turn your roots into a messy, ineffective sludge. Once it takes hold, it’s almost impossible to shift.
If the substrate remains sodden, cannabis leaves drooping will be the least of your problems. Various microscopic pathogens like algae and fungi can kill your plants. Ensure drainage isn’t to blame for your curling cannabis leaves.
The same applies to the flowering phase when too much phosphorus or potassium causes cannabis leaf twisting.
Most regular growers will already have experience with nutrient burn. This is when cannabis leaves show burnt brown tips similar to heat stress effects.
Weed leaves curl and claw, or even cannabis leaves canoeing is possible. If left unchecked, chlorosis (abnormal coloration of leaves) is likely.
Cannabis is a weed and grows easily in many climates, but temperatures above 86⁰F are incompatible for most strains. Matching extreme heat with low relative humidity is a recipe for trouble, and they’ll let you know with curling weed leaves.
Unable to photosynthesize when it’s hotter than 86⁰F, leaves might curl, canoe, and droop. Cannabis leaves can also yellow, fall off, or turn crispy and brown. New growth will often be deformed due to high temperatures. Heat stress can occur both in and outside.
The opposite end of the viable growth spectrum for cannabis is around 50⁰F. Short stints at lower temperatures are not the problem, but extended periods are. The first sign that your crop isn’t enjoying its cool environment is the cannabis plant leaves curling.
If temperatures don’t rise, you risk permanently stunting the growth of your plant, and they may not even enter the flowering phase. If they do, yields will be low with loose or leafy, partially-formed buds.
Many growers use cooler temperatures late in bloom to elicit gorgeous purple or blue colorations. These are only overnight (or dark phase) dips, though. Prolonged exposure to low temps will first make marijuana leaves curl up and eventually kill the plants.
Breeders are continually creating new cannabis cultivars. They marry particular traits in the hope of producing the next super-strain. Genetic mutations in cannabis plants are a part of that evolution, and some tend to grow curling cannabis leaves.
Some varieties are prone to negative effects from the addition of nutes. Some sativas and autoflowers may present symptoms of leaf curl purely due to their genetic makeup.
Weed leaves curling down: What does it mean?
Your marijuana leaves curling could be a result of overwatering or underwatering. The symptoms are similar, so experience helps in differentiating. Getting this right is all-important to the future health of your harvest.
If your foliage is wilting or withering with cannabis leaves curling down, you’re probably underwatering your crop. Check to see if the tips are curling and losing their green hue. You may also note the lower leaves on the stem start to yellow, die, and fall off.
By contrast, when cannabis leaves start drooping down, looking tired and heavy, you may be overwatering them. The whole leaf curls and droops not long after watering, but they retain their shape.
If overwatering continues, growth slows right down, and the leaves may also start to yellow. It happens because the roots aren’t taking up nutrients, either.
Leaves canoeing up? 5 ways to fix it
We outline five ways to halt leaves curling up on weed plants. It’s important to take stock and be proactive at this time, as waiting will only exacerbate the issue.
If you think you may have overwatered your plants, let the roots dry out for a few days first. The soil should be completely dry to about two inches, improving transpiration and oxygen intake. Check by pressing two fingers into the soil before you add more H2O.
While watering should be consistent, it doesn’t need to be every day. If you’re unsure, underwatering is better than overdoing it, so leave it an extra day. Some growers combat the potential for weed leaves curling up by using drip irrigation or sprinklers with timers.
Growers need to rinse the roots with water to clear out excess nutrients to fix the problem of pot leaves curling up from overfertilization. Then it’s back to the drawing board. Start again from scratch and ensure you feed your plants at the lower end of concentration.
Make sure you follow the manufacturer’s recommendations and directions. If the problem persists, change your fertilizer.
Heat stress fix
The remedy for heat-stressed plants depends on where you are growing them. The plants are probably too close to the lights if you’re growing indoors.
As your plants grow taller, you’ll need to maintain a certain distance between the top of the crop and the warm lights. Otherwise, they’ll get stressed and you will get curled cannabis leaves as a result.
Outdoors, it’s not so easy to regulate your environment. Heatwaves are impossible to prepare for, but you could erect a screen to trim the temperatures. This might reduce the effects of direct sunlight to acceptable levels, potentially healing your curling leaves on weed plants.
Unless you leave your crop to fend for itself, watering by hand or a sprinkler system can ease the effects of drought.
Too cold fix
Growing indoors or out makes a huge difference to your options if you have cannabis leaves curling up. Indoor growers can use heaters or insulation, but increasing the number of lights would also help.
Outdoor growers have fewer alternatives. If your locale is prone to lower temperatures, consider building a greenhouse or another structure that can insulate your plants. Depending on the flowering status, you may need to harvest your crop earlier.
Once the plants are growing, there’s not much you can do. Clip off curly leaves and hope new growth improves. Avoid using that particular strain in the future if things do not improve.
Choose your cannabis strains carefully. If you provide your marijuana plants with the best environment possible, you’ll limit the potential for leaves curling up weed.
3 strains that will help you avoid weed leaves curling up
Some cannabis strains are very forgiving and recover rapidly from errors that could lead to curled cannabis leaves. Certain varieties perform well under extreme conditions and below are three of the best:
Northern Lights feminized is an iconic cultivar boasting epic yields, Cannabis Cup-winning genetics, and super-swift flowering of just 6–8 weeks.
An indica-dominant blend of two landraces (Afghan indica and Thai sativa), these genes are extremely stable, and leaves canoeing up are virtually unheard of.
Medium to high THC values (14–17%) provide euphoria, but relaxation is why most users gravitate towards this classy choice.
The harvest can yield over 17 oz./m² indoors and an incredible 31 oz./plant in the open. Lemon and other sweet citrus flavors dominate the palate, with hints of skunk.
Blue Dream feminized is a popular sativa-dominant hybrid combining legendary sativa Haze and breeder DJ Short’s incredible Blueberry. These plants grow easily indoors and outside with award-winning genetics, fewer curling cannabis leaves, and a delightful flavor profile.
Crops produce hefty yields (up to 21 oz./plant outdoors) that match high THC levels (16–20%). Indoor growers must change the lighting schedule to 12 on, 12 off to induce flowering. Reap a generous 21 oz./m² after only 8–10 weeks of bloom.
Feminized seeds are easier to grow as you won’t have to sex and remove males. Tried and tested genes mean the plants ward off pests, and the chances of your cannabis leaves curling are limited.
An African landrace strain, Durban Poison feminized is one of the few pure sativas available. It’s especially easy to grow outdoors in ideal conditions, and pure genetics means you’ve less chance of pot leaves curling up.
Indoor growers can harvest up to 16 oz./m², while outdoor yields peak at 21 oz./plant. Sweet pine and earthy tones highlight the flavor profile, while the effects combat fatigue.
The pure and stimulating sativa combined with 13–16% THC values provides uplifting and mind-altering effects. Users claim it helps with stress and depression, and this is no leaf curl cannabis either.
The ups and downs of cannabis leaf curl
Cannabis seedling leaves curling down stresses the grower out as much as the plant, and it’s vital to make the correct diagnosis.
Overwatering is the likeliest culprit, but underwatering can provide similar symptoms. Overdoing the nutrients is a regular offense, while deficiencies can also see cannabis leaves curling up.
If your local environment is very hot or cold, consider cultivars from similar climates. You could look into Mexican or Cambodian strains if it’s exceptionally hot.
Autoflower strains handle cool temperatures thanks to their Eastern European ruderalis influence. Order from a reliable supplier as unstable genetics can result in marijuana leaves curling.
Now you have the information to prevent cannabis leaves canoeing, and you know how to create a successful homegrown crop. All you need is cannabis seeds that complement your local climate.
Homegrown Cannabis Co. has over 500 epic strains to match every conceivable environment. We’re sure to have you covered and deliver nationwide within days, so order yours today.
About the Author: Kyle Kushman
Kyle Kushman is a legend in the cannabis community. He is the modern-day polymath of pot: cultivator, breeder, activist, writer, and educator. After winning no less than 13 Cannabis Cups, there’s nothing this guy doesn’t know about indoor growing – he’s been there, done it, and is still doing it to this day!