Why Are My Cannabis Leaves Wilting?

You want your cannabis plant's leaves to be vigorous and thriving, but what if the leaves are wilting?

Wilting is defined as the loss of sturdiness or rigidity of leaves. It's a common problem many growers face. 

Sometimes, it is due to lack of experience or human error, and other times, it's just bad luck. And it is caused due to various issues. Learn what these issues are and how to treat your plant in this article.

1. Heat Stress

Perhaps the most common cause of wilting leaves in cannabis is heat stress. Cannabis typically grows best in warm temperatures, but sometimes, it can be a little too much.

Too much heat can cause several problems in your plant that can severely affect its health, and in severe cases, it can even kill your plant. It can also affect the buds' quality and yield.

Causes of Heat Stress

Cannabis is a resilient plant, but sometimes, the temperatures are too high in your grow room for the plant to handle — this is the most common cause of heat stress. However, some other factors can lead to heat stress, too, like:

• Low humidity that makes it harder for your plant to stay cool.
• Excess nutrients or minerals can cause nutrient burn, disrupting the plant's temperature regulation abilities.
• Intense light that's either too close to the canopy or too bright for the plant.
• Poor ventilation leads to stagnant air and heats the room over just a few hours.
• Air conditioner failure.

But plants are smart, and they show signs of discomfort early. Moreover, these symptoms largely depend on the plant's growth stage since the plant's temperature requirements change as it grows.

Symptoms of Heat Stress

Here are some of the most common symptoms of heat stress that you must look out for, apart from wilting leaves:

• Leaves curling upwards around the edges.
• The seedling may experience stunted growth, pale or withered leaves, or death in the seedling stage.
• In the vegetative stage, the leaves may wilt, curl or dry, have brown spots, or have burnt leaf tips.
• The leaves appear bleached, curled, or yellow in the flowering stage. The plant may develop foxtail buds or produce white pistils prematurely.

If you identify these symptoms on your plant, it is probably suffering from heat stress.

Protecting Your Plant Against Heat Stress

You must protect your plant against heat stress to cure the problem and avoid it in the future. These remedies depend on whether you are growing your plant indoors or outdoors. Below are some ways to protect your plant from heat stress based on the growth environment.

Indoor Cannabis Plants

If you are growing your plant indoors, you need to remedy the growth environment to suit your cannabis plant. 

The first step is to check the efficiency of the equipment, especially the air conditioner and humidifier, to ensure ideal temperatures within the grow room. 

Next, you must install the right exhaust fans or air conditioner if you live in a warm region. An exhaust ensures the air within the grow room stays fresh and at a low temperature. 

Ideally, your grow tent or room's temperature must be around 25°C. 

Also, if you are using HID lights, you need to be extra careful. HID light panels produce a lot of heat that can increase the grow room's warmth. So, check your HID lights distance to the canopy.

If the top tier of the plant shows symptoms of heat stress, it is likely due to your lights. In this case, you can upgrade your lights to LED ones or increase the distance between your HIDs and the canopy. 

Outdoor Cannabis Plants

If your plant is experiencing heat stress outdoors, it's slightly more challenging as controlling the heat outdoors is harder. Yet, there are a few things you can still do, such as the following:

• Move the pots to a shaded area during the warm hours of the day.
• Use large containers or ceramic pots with higher moisture retention abilities than regular pots, which helps keep the plant cool.
• Use kelp extract — a nutrient-rich seaweed supplement — that regulates the temperature and humidity at the root zone, preventing your plant from drying out.
• Water your plant during the dawn when the sun is not so warm.
• If you cannot move the plants, build a simple shade for the plant using sticks and cloth sheets during the hot hours of the day.
• Choose heat-resistant strains like Sour Diesel, Blue Mystic, or Amnesia Haze.

Your plant experiencing heat stress is not the end of the world, but you must act quickly to help your plant recover. 

2. Hemp Russet Mites

Hemp russet mites, belonging to the eriophyid family, are tiny pests that are difficult to spot. And they reproduce quickly. 

These pests have a 0.2 mm elongated body with a pale shell and four legs, and they transform into a fully-grown adult within a month. Plus, the female ones can lay up to 50 eggs once they mature. 

Hemp russet mites are also quite contagious, especially when they are young, because they get caught in the wind and can be carried away onto other plants.

They typically feast on young cannabis leaves, buds, merismatic tissues, and petioles of your plant, beginning at the bottom and moving upwards towards the buds. And it would help if you eradicated them immediately because they can cause nutrient deficiency and other serious health problems in your plant.

Symptoms of Hemp Russet Mites

If only spotting hemp russet mites was easy! But it is not. Fortunately, symptoms of their infestation are pretty easy to detect. Here are the most common symptoms:

• Wilted or curled up leaves
• Leaves turning yellow or bronze
• Necrotic spots showing on the leaves
• Brittle petioles that eventually fall off
• Stunted or rough leaf growth with stooping plant
• Pistils turning dark
• Stunted bud growth or even death

Getting Rid of Russet Mites

You can get rid of russet mites quite quickly, but it can take some days. Use the following methods to eradicate hemp russet mites from your plants.

Use Essentria IC3 or Neem Oil

Perhaps the best way of getting rid of hemp russet mites is by using Essentria IC3 or neem oil. These pesticides can quickly kill these mites without harming your plant, and you can buy them at your local horticultural stores for a reasonable price.

Simply mix the pesticide in water and spray on your plant as directed by the manufacturer.

While these pesticides are natural, they can still be harsh on your plant. So, never spray them when the lights are on — this can cause the leaves to burn up — and never spray them on the buds as they can compromise their flavor and aroma.

Use Micronized Sulfur

If neem oil or Essentria IC3 do not work, you can use micronized sulfur, too. 

Simply dilute the sulfur in the water, as per the manufacturer's recommendations, and spray the mix on your plant at least thrice every week.

Since this compound is harsher, do not use it with other oil-based products. Oil can encapsulate the sulfur, leading to sulfur burns. Before using any other product, rinse your plants thoroughly with water. Next, wait for 3-4 days for the sulfur to be eradicated from the plant.

Predatory Pests

If the infestation is not severe, you can even use predatory pests that hunt down the mites and kill them. Pests like Amblyseius cucumeris (Cucumeris), A. swirskii (Swirskii mites), and Amblyseius andersoni can feed on these pests 24/7!

Preventing Hemp Russet Mites

Simply eradicating these mites is not enough. You need to ensure they never come back. Follow these tips to prevent them from entering your grow room again:

• Try to grow cannabis plants from seeds rather than getting clones from dealers, as these mites can't survive on seeds.
• Before introducing new plants to other plants, always quarantine them and check for any signs of mites.
• Avoid over-fertilization of your plants as it can invite these pests to your plant.

3. Nitrogen Deficiency 

Nitrogen is one of the three essential macronutrients your plant needs to survive and grow, especially during the vegetative stage. No doubt, it is one of the NPK compounds that help your plant thrive and bloom.

Plus, nitrogen is essential for photosynthesis and producing amino acids (building blocks of proteins). Even the plant's DNA relies on nitrogen. 

Causes of Nitrogen Deficiency

Given the importance of nitrogen for your plant's health, a lack of it can be disastrous. Nitrogen deficiency is caused due to the following reasons:

• Low nitrogen amount in the nutrient solution or grow medium.
• Incorrect pH levels in the medium may affect nitrogen uptake.
• Damaged root systems, where the roots may fail to absorb adequate nitrogen.
• Excess zinc, potassium, chloride, or manganese in the growing medium inhibits nitrogen absorption.

Symptoms of Nitrogen Deficiency

Fortunately, nitrogen deficiency is easy to spot in cannabis. 

The first symptom of nitrogen deficiency is that the leaf tips start losing their color, turning yellow or pale, and the leaves wilt. Eventually, the leaves turn brown, wrinkle, and fall off.

However, since nitrogen is a mobile nutrient — it moves from the bottom to the top of the plant — you get enough time to act and reverse the damage. In short, the leaves at the bottom show deficiencies at first, and it slowly travels to the top parts. 

Solving Nitrogen Deficiency

There are multiple ways to solve nitrogen deficiency, depending on the cause. First, understand the symptoms mentioned above, figure out what is causing the problem, and act accordingly. Use the following methods.

Use Nitrogen-rich Growth Fertilizers

The most probable cause of nitrogen deficiency in cannabis is improper NPK levels in the fertilizers. So, you can use fertilizers with high nitrogen levels to stabilize the NPK levels in the growing medium or nutrient solution, and these can be purchased at your local horticultural store.

Your best bet is using water-based fertilizers — they are easy to use, effective, and reach the root directly, ensuring faster recovery.

The best nitrogen-rich fertilizers for cannabis plants are worm castings and blood meal.

Worm casting, essentially earthworm poop, is an organic fertilizer rich in various soil minerals, especially nitrogen.

On the other hand, blood meal, or animal blood, is another organic fertilizer that contains a lot of nitrogen. However, be careful when using blood meal since they have very high nitrogen levels, which can cause a nitrogen lockout or turn your medium too acidic.

You can even use cottonseed meal or bat guano if you cannot find blood meal or worm castings nearby.

Correct the pH Levels

In the growing medium or nutrient solution, incorrect pH levels can lead to root problems, inhibiting nitrogen uptake. 

So, check and correct the pH balance of the medium and nutrient solution. If you're growing in soil, the ideal pH must be 6 to 7. For hydroponic methods, the pH must be between 5.5 to 6.5. 

An excellent way to check the pH is by measuring the pH of the nutrient solution and the runoff water — doing so would give you an accurate reading of the growing medium's pH.

Also, note that various cannabis strains naturally show signs of nitrogen deficiency once they enter the flowering stage. This is because the plant stops absorbing too much nitrogen to focus on bud development.

If that is the case, do not give your plant more nitrogen as it can delay the harvest. Instead, use bloom-specific fertilizers that come with low nitrogen levels.

4. Incorrect Watering Cycles

Watering is crucial for your plant, but watering your plant isn't as simple as it sounds. Too little or too much water can cause various health problems for the plant. So, let's take a look at both watering issues in detail.

Overwatering 

Overwatering is a common mistake in novice growers, but it can cause the roots to drown since plants use the roots for breathing air. 

The common symptoms of overwatering include the following:

• Drooping or wilted leaves. 
• Curled or thick leaves due to too much water content.
• Stunted plant growth due to lack of adequate air.
• Yellowing of leaves, which is a nutrient problem, is a common side effect of overwatering.

If you spot these symptoms, avoid watering the plant too frequently and wait for the soil to dry before watering again.

Underwatering

On the other hand, underwatering can also cause your plant's leaves to wilt. When the plant's water demands are not met, the root zone dries out, which causes poor water and nutrient uptake, affecting the plant's growth and yield.

Another common cause of underwatering is the incorrect pot size. For instance, a small plant (with a small root ball) growing in a large pot would be unable to consume all the water from the grow medium.

The most common symptoms of underwatering are:

• Weakened plant structure since water is crucial for the plant's physiology. 
• Wilting leaves.
• Papery or fragile leaves. 
• Crispy soil or dry grow medium.

If you notice these signs on your plant, increase the watering frequency until your plant recovers and try your best to maintain regular feeding schedules later on. 

Tips for Correctly Watering Your Plant

Fixing the problems associated with incorrect watering is easy. Just follow these tips:

• Water the soil when it is dry to give the roots enough time to breathe. 
• Check the soil's dryness by inserting your index finger into it — if it's dry, water the medium.
• Ensure adequate drainage from the medium since lack of it can lead to the root zone drowning.
• If you have compacted soil or notice overwatering symptoms, it may be due to poor air retention in the growing medium. Use aerating substances like perlite or vermiculite in the medium to fix this.
• Monitor the growing medium and water solution's pH levels. 
• Ensure you are growing your cannabis plant in the right-sized pot.
• Never water your plants when the lights are off to optimize oxygen balance in the root zone, maintain humidity levels, and prevent nutrient burn.

Ideal Watering Schedules for Each Growth Stage

Like any other macronutrient, your plant consumes water in different amounts during each of its growth stages. Take a look at how to water your plant during each of its growth stages.

Seedling stage

Seedlings grow best in a moist environment, not a soaked or dry one. So, use a propagator to water seedlings and maintain a relative humidity of around 70% during this stage.

Vegetative stage

During the vegetative stage, the plant gets thirstier as it has to grow the most during this period. So, water your plants 1 to 3 times a week.

Remember, this is only a rough guide. Your plant may require more or less water during this phase. Listen to your plant and schedule watering accordingly.

Flowering stage

Water is crucial during the flowering stage since bud development depends on it. So, listen to your plant and feed it adequate water during this period.

Also, use flowering-specific boosters and fertilizers to optimize water uptake, encourage vigorous growth of the buds, and avoid overwatering your plant at all costs during this stage.

5. Root Rot

Root rot or slimy roots is another problem that shows itself in the form of wilted leaves. This issue occurs when the root zone is not optimal for the roots to thrive, which stresses out or shocks the roots.

When the roots are stressed, various organisms like fungi, bacteria, and algae attack the roots, turning the surface into brown slime. This slime further stresses the roots, inhibiting the intake of nutrients, water, and oxygen.

If this issue is not fixed immediately, it can eventually kill your plant.

Causes of Root Rot

Root rot is typically caused due to the following factors:

• Excessive heat increases the chances of bacteria and fungi infestation in the root zone.
• Excessive cold can stress out the roots.
• Light leaks in the root zone, nutrient reservoir, or hoses encourage fungi and bacteria growth. 
• A dense or compact medium that causes a lack of air pockets within. 
• Incorrect hydroponic setup.

Symptoms of Root Rot

While root rot may not be visible — since it's under the medium — you can still identify it with various other signs, such as the following:

• Burnt or curled leaf edges 
• Brown or yellow blotches on the leaves
• Wilting or drooping leaves
• Signs of nutrient deficiency 
• Stunted plant growth
• Decreased water consumption
• Mushy stems and branches
• Nasty odor in the soil 
• Slimy roots

Fixing Root Rot

Root rot is difficult to fix, but you can still save your plant if you act quickly. Follow the below tips to salvage your cannabis plant.

Verify the Growth Environment

First, you must check the environmental factors like humidity, temperature, watering frequency, etc.

Ideally, the root zone, water reservoir, and adjoined hoses must be light-tight.

The humidity should be:

• 65% to 70% during the seedling stage
• 40% to 70% during the vegetative stage
• 35% to 40% during the flowering stage

The temperature should be:

• 20 to 28 degrees Celsius during the seedling and vegetative stage
• Around 23 degrees Celsius during the early flowering stage
• And 18 to 24 degrees Celsius during the late flowering stage

Also, refer to the recommended NPK levels for your cannabis strain and correct them if needed.

Treat the Plant

Next, remove the plant from the grow medium and rinse the roots under running water to wash off the slime.

Then, use disinfected scissors to cut any damaged parts of the roots.

You can also dip the roots in 3% hydrogen peroxide for a few seconds and let them dry for a few hours.

Flush Your System

You then have to flush the entire system by flushing the nutrient solution and running 10% bleach with water through the system for a couple of hours.

Replant the Plant

Next, add the nutrient solution to the reservoir and add beneficial bacteria like Hydroguard, Voodoo Juice, and Rooters to the medium to protect the roots.

You can also add air stones to the growing medium to improve air retention.

Once everything is ready, replant your cannabis into the grow medium.

Preventing Root Rot

It is always better to prevent root rot than to solve root rot. Follow these tips to avoid it:

• Start with a healthy substrate even before planting your cannabis.
• Use high-quality soil with adequate aeration so it does not get compact over time.
• Ensure a correct watering frequency to avoid water saturation in the growing medium.
• Maintain a clean, ventilated grow environment to prevent mold and fungus infestation.
• You can even add root boosters to the grow medium to encourage better root health.

Summary: Why Are My Cannabis Leaves Wilting?

Wilting leaves are common in cannabis plants. They can occur due to various issues, like the ones mentioned above. Use this article as your guide to narrow down to the actual problem and work on fixing it. Then, work on preventing the same issue in the future.

If you act quickly, you can save your plant. 

But whatever happens, do not lose hope. You can solve most problems with cannabis plants with some dedication, time, and effort. Fix your plant and stay tuned to know more about protecting your plant from other problems in the future.