15 Cannabis Leaf Problems And How to Fix Them

If you have just begun growing cannabis in your home, you will face a few problems. But, unfortunately, that's part of the parcel with growing cannabis. These problems can be anything, from nutrient imbalance, improper watering schedule, or simply having your grow light a little too close to the plant.

It's part of the learning process, but what do you do if you face such issues? 

You look at the leaves — they reflect your plant's health more than you think. And in this article, we show you some of the most common leaf problems you may face while growing cannabis, what they mean, and how you can fix them.

Crispy Leaves with Burnt Edges

In the endeavor to give your plant the best nutrients, many new growers go overboard and feed it too many nutrients. However, rather than making the plant stronger, as expected, it causes a nutrient burn — a sign of stress that the nutrient solution is too strong. 

Typically, the nutrient burn will make the edges of your leaves brown, give it a crispy texture, and stunt your plant's growth significantly. And this always starts at the leaf tips and moves inwards.

If the leaves look crispy with burnt edges, you need to start acting quickly by holding off on feeding it nutrients. Wait for a couple of weeks, flush the medium with pH-balanced water, and resume once the leaves start healing. 

Flushing the medium will deplete the excess nutrients, giving your plant a fresh start.

However, don't use the same ratios this time. Instead, turn down your nutrient solution, see how your plant reacts, and tune it accordingly.

Drooping Leaves with Stunted Plant Growth

Watering your cannabis plant can be a bit confusing. Often, growers err on the side of caution by giving less water. However, not giving your plant enough water can cause various problems for the plant.

Underwatering shows up as drooping leaves and stunted plant growth in most cases.

If you notice this sign with your plant, don't worry. This issue is quite easy to fix. Immediately water your plant, and within half an hour, your plant will perk up again.

And in the next watering, feed more water to the medium until you see some of the water running off from the bottom of the medium. The runoff from the drains must be around 20%. However, if you're a beginner, proceed with caution. You don't want to water too much or you'll end up overwatering. To be on the safer side, water just a bit, watch how the plant reacts in the next 24 hours, and then water more if it's still droopy. If the plant has perked up, you don't need to water more. 

Yellow, Curled Up, and Burnt Leaves

An overdose of nutrients for the plants is terrible, and so is too much light. So, if you have placed your light panels too close to the plant or are using high-powered lights, it can cause your plant to experience light burns.

The common symptoms of a light burn in cannabis include yellowing, curling, and burnt leaves. And these symptoms start exhibiting at the top of the plant since it's closer to the lights.

If you notice these signs on your plant, you must immediately raise your light panels at least 6 to 12 inches from your plant's top and wait for it to recover. 

We also recommend taking a look at your light's owner's manual. Most light manufacturers include the recommended distance for the plant's each growing stage. Follow it religiously, but if you still notice light burns, your light system may be too intense for the plant. Consider downgrading.

Yellow Leaves with Burnt Edges

If your plant's leaves turn yellow with burnt edges, it's a sign that you are not feeding it pH-balanced nutrients and water. The pH of the nutrients, water, and grow medium is exceptionally crucial for your plant as it affects how well the roots can absorb the nutrients. 

And if the pH is off, the roots may not be able to absorb the nutrients properly, causing a nutrient lockout of the plant, essentially a shock for the plant. This shock can exhibit itself in various symptoms, from nutrition deficiency, wilting, falling leaves, and a lot more. 

If you notice this, we recommend flushing the grow medium with pH-balanced water. Then, refeed the medium with a pH-balanced nutrient solution.

The ideal pH must be around 5.5 to 6.5.

To ensure the pH balance, always compare the pH balances of the water you feed and the runoff water. The runoff water is the most accurate way to check the growing medium's pH balance. Then, tune the pH accordingly. 

You can even buy pH-balancing solutions from your nearest gardening store. These solutions are easy to use — follow the instructions and mix the right amount into your nutrition solution to balance the pH.

Yellow Leaves on the Lower Tiers

Image credit - Wicked_Stix

Your plant needs three essential macronutrients, also known as NPK, and out of these, the most important one is nitrogen. 

Nitrogen is essentially the building block for your plant as the tissues are mostly nitrogen. If you accidentally give it inadequate nitrogen, the plant will stop growing entirely with nothing to harvest at the end. 

But before it reaches that stage, nitrogen deficiency shows other symptoms. One of them is the yellowing of leaves on the lower tiers of the plant, quickly making its way up.

If you notice this sign on your plant's leaves, you must act quickly. 

First, flush the growing medium with pH-balanced water to remove residual nutrients. Then, reach out to your nearest horticultural store and get yourself some water-soluble nitrogen fertilizer. Mix it in water and feed it to your plant immediately. The plant will absorb it quickly and recover soon.

That's not all. You also need to rebalance the NPK ratios in your nutrient solution and check the pH balance of the same.

The ideal NPK ratios for cannabis are:

• 3:1:1 of nitrogen, phosphorus, and potassium during the vegetative stage
• 1:3:2 for the mid-bloom stage
• 0:3:3 during the late flowering stage

Follow these ratios and tune them to your plant's strain. 

Rusty Leaf Tips on the Main Stem

Image Credit - Sensiseeds

Potassium is another macronutrient that's necessary for your plant. It helps transport water from the roots to the rest of the plant.

If there is a potassium deficiency in the nutrient solution, it can trigger several problems. One of the most visible of these problems occurs on the leaves in rusty spots along the edges of the primary stem leaves.

But if you don't fix it on time, it can lead to smaller buds, and your plant will become more prone to diseases. 

To fix this, use some good potassium-rich fertilizers like potassium bicarbonate, potassium sulfate, liquified kelp, and potassium silicate. And recheck the NPK levels in your nutrient solution, as mentioned earlier.

Leaves Turning Blue-Green with Brown Blotches

Image credit - xbabybitchx

Your plant may also experience phosphorus deficiency. And phosphorus is the third component of the NPK macronutrients, which helps grow sturdy roots, stems, and big buds. 

One of the signs of phosphorus deficiency is the lower and older leaves turning blue-green with brown blotches. The leaves may also feel stiff or dry to touch. 

To fix this issue, begin with flushing the grow medium with clean water. Then, add some phosphorus-rich fertilizers to the growing medium. Some of the best nutrients rich in phosphorus include bone or blood meals, worm casting, crab shells, soft rock phosphate, and fish meal.

Brown Spots on the Upper Leaves and Lower Leaves Curling and Twisting

Image Credit - Uncleremus

The cannabis plant relies on calcium to grow strong cell walls and stems that support other organs and protect itself against environmental stresses like hot weather. 

However, if you fail to give enough calcium to your plant, it can quickly start showing signs of stress that, if not fixed, can weaken your plant and reduce your yield. 

If you notice any copperish, brown, or yellow spots on the upper leaves along with the lower leaves curling and twisting, it is a sign of calcium deficiency. 

To fix this issue, begin with checking the pH levels of the growing medium. If the pH levels are imbalanced, flush the medium immediately and correct the medium because improper pH can stop the roots from absorbing calcium properly.

Next, add a calcium-rich fertilizer to the medium with calcium, magnesium, and iron. We recommend adding magnesium and iron because calcium deficiency usually occurs with magnesium and iron deficiencies. Your best bet is cal-mag supplements to add in your nutrient solution or the growing medium.

Yellow Leaves with Green Veins

One uncommon but scary leaf problem growers face is the leaves turning yellow outside the veins. This symptom is a sign of iron deficiency. Within a few days, these leaves start showing signs of burning and eventually fall off. 

You must fix this issue quickly, too, because it can stunt your plant's growth and affect bud development, leading to lower yield during harvest.

To fix iron deficiency, let the growing medium dry out. Then, flush it with pH-balanced water. Next, you need to adjust the grow medium's pH to 6 to 6.5 because iron gets best absorbed in this range.

Once you have flushed and rebalanced the grow medium, you can start adding iron supplements to the feeding cycle as recommended by the supplement manufacturer. Within a few days, your plant will start recovering.

Taco Leaves (Leaves Folding Up Longways)

Image credit - OGProbs

Tacos are love, but not when they start appearing on your cannabis leaves. If your plant's fan leaves are folding up longways, it's due to heat stress. 

Heat stress is generally caused due to high temperatures or too intense grow lights. You must fix this issue as soon as possible to prevent stunted growth.

Ensure your climate control is working correctly and is set at the right temperature. The ideal temperature for the cannabis plant is around 75°F to 82°F (23°C to 27°C — anything over this may cause heat stress to your plant.

Next, ensure the ventilation system and the fans are working correctly. Stagnant air can raise the overall temperature of your grow room, which can also cause heat stress.

Don't forget to check your grow lights too. Even if your lights are set at the right distance from the plant, they may still heat up a lot, causing heat stress. 

If that's the case, we recommend upgrading your lights to LED lights that don't heat up too much or installing air-cooling to your light panels. Using bigger lights is good for the yield, but too much of it can backfire, causing smaller yields.

Powdery Mildew on the Leaves

Cannabis leaves must be lush green, but if you notice any powdery stuff on them, it is most probably mildew, a common fungus that grows in high-humidity regions.

Unsurprisingly, mildew grows on your leaves if your grow room's humidity is too high or has low airflow. And it would help if you fixed this immediately. Otherwise, it may spread quickly and eat up your plant.

The best way to remove mildew from your cannabis leaves is to spray mold-eliminating spray on them. Remember never to spray the buds as these sprays can affect the flavor and smell of the buds.

Next, check your grow room's humidity levels. Ideally, the humidity of your grow room should be:

• 70% to 80% RH for the seedling stage
• 50% to 80% RH for the vegetative stage
• 40% to 50% RH for the flowering stage

You must also upgrade your ventilation and fan system in your grow room. Use a variety of fans, including oscillating fans, to distribute the air properly within the grow room to increase airflow.

Brown, Moldy Buds and Leaves

Like mildew infestation, mold can also grow on your cannabis plant. If you notice your leaves and buds turning brown and moldy from the inside, it's a sign of mold infestation. If ignored, mold can take over your plant and ruin your precious buds.

Typically, mold is caused due to overwatering, high humidity, or low airflow. 

To fix mold on your cannabis plant, first mist the plant with mold-eliminating spray. Then, check your grow room's humidity and airflow, as mentioned in the previous section. 

Once everything is set correctly, you may still see mold on the buds. Unfortunately, there is nothing you can do about them. Cut the infected buds and dispose of them — they are useless anyway. 

Mold may sometimes go on the surface but return in a few days. So, keep a close eye on your cannabis plant and regularly check for any signs of mold.

Tiny, Light-Colored Spots Under the Leaves

One of the biggest nuisances while growing cannabis is pest infestation. They are perhaps the most damaging to your plant and challenging to get rid of. And the worst of all are spider mites.

These tiny pests are notorious for ruining cannabis cultures around the world. They are small, practically invisible to the naked eye, and typically reside on the underside of the leaves. And they multiply rapidly as they can lay hundreds of eggs each day. 

Spider mites crawl around the leaves, nibbling on the soft tissue and sucking all the nutrients from the plant. This can cause several problems, including nutrient deficiency, for the plant. 

And on the leaves, spider mites cause light-colored speckles, as dots close together. So if you notice these dots on your leaves, it's a sign of spider mites. You can use a trichome scope to verify their presence on your leaves. (Hint: they look like spiders.)

You must eliminate them immediately; they are notorious for multiplying in a few days and become impossible to destroy if you wait too long.

The best way to get rid of spider bugs is spraying organic pesticides on the leaves; never spray the buds, though, as it can affect their taste and flavor. 

We don't recommend using chemical-based potent pesticides, as they can leave a nasty smell on your plants and alter the buds' flavor and smell.

If you don't want to use pesticides, you can even leave some ladybugs on the plant. These cute creatures love feasting on mites quickly, and you can buy them at your nearest gardening store for as low as $10. 

However, it is already too late if you notice spiderwebs on your cannabis plant. So, always comb through your plant every few days to look for spider mite infestation regardless of whether you see the signs or not.

Lethargic, Wilting, Yellowish Leaves

Another common pest that can affect your cannabis plant is aphids. These pests live on the fan leaves' underside; they are green in color and have long legs like a grasshopper. And they are quite tiny, almost invisible to the naked eye. 

They spend their life crawling around on the underside, sucking the water and nutrients from the fan leaves. This causes the leaves to wilt and turn yellowish. Aphids may not seem as dangerous as spider mites, but they can kill the plants just as fast. 

If you suspect an aphid infestation on your plant, use a trichome scope to check for aphids under the fan leaves. If you find these little pests crawling around, it's time to eliminate them. 

You must fix the issue promptly. Because if you don't, these pests can do a lot of damage to your plant and reduce your overall yield. The good news is that it's not very difficult to get rid of aphids. You can start by hosing the infected sites with lots of water. Just make sure you get as many aphids dislodged as possible. You can also try neem oil mixed with soap water for great results. Try your best to stick to organic products and avoid chemical-based pesticides.

You can bring some ladybugs into your grow room if you don't like using pesticides out of fear of affecting the buds. 

Ladybugs love eating aphids, so add a few of them and let them take care of the rest. 

Once you have eliminated them, don't rest yet. Keep a close eye on the plant to check for any signs of aphids under the leaves. 

Downward Curled and Rigid Leaves

Image credit - Mister_X

If your cannabis plant's leaves curl downwards and feel rigid, that's because they are full of water, a sign of overwatering. 

Another symptom of overwatering is stunted growth, and if you don't fix it soon, the plant can develop root rot. 

So, the first thing you must do is not water the plant for a couple of days. Let the soil dry completely. Then, lower your watering frequency and learn how much water your plant needs.

As a general rule of thumb, you must only water the plant when the soil is dry. You can check the soil by pressing your finger into it — it should be dry until one inch deep. 

And when you are watering, always let some water drain out of the bottom. The runoff water from under the growing medium should be around 20%. If it doesn't drain, you need to check the drainage holes for clogs.

Summary: 15 Cannabis Leaf Problems And How to Fix Them

Cannabis is a sturdy plant and can withstand harsh environments, deficiencies, and invaders. However, you shouldn't always risk it. Risking the chance of problems is risking your precious buds. You must fix any issues with your plant promptly. 

Fortunately, these problems are often reflected in your plant's leaves. So, you can tell a lot about the plant's health just by looking at it. For example, the leaves can tell you whether your plant is facing a particular nutrient deficiency, dealing with pests or mold, or experiencing stress due to environmental factors.

So, regularly look at the leaves and learn to identify abnormalities. If you spot any, use this article to compare the symptoms and determine what's causing that. And then fix the problem before it is too late.

And remember, each cannabis plant is different. The genetics of each strain differ a lot, and their reaction to the environmental conditions also differ. So, understand your plant's genetics well so you can quickly fix what's broken soon.

We recommend asking questions here on Growdiaries and talking to other growers growing the same strain of cannabis to know the exact fixes for your plant's problems. This is much better (and safer) than trial and error methods.