How to Deal With Cannabis Root Rot

Discover how to deal with cannabis root rot by identifying causes, implementing effective treatments, and preventing future occurrences in your plants.

How to Deal With Cannabis Root Rot

Identifying, treating and preventing cannabis root rot is an essential part of keeping your plants healthy; this blog post will explore how to address this common problem. Affecting both novice and experienced growers alike, understanding the causes of cannabis root rot can help you maintain a thriving garden.

We will delve into the various factors that contribute to the development of root rot in your cannabis plants and provide actionable solutions for treating affected plants. Additionally, we'll discuss preventive measures such as checking soil pH levels, reducing water frequency, and introducing beneficial bacteria or fungicides to keep your plant's roots healthy.

Armed with this knowledge on how to deal with cannabis root rot effectively; you'll be well-equipped to ensure your plants' success throughout their growth cycle.

Table of Contents:

Identifying Cannabis Root Rot

As a cannabis grower, it's important to be aware of any potential issues that could threaten the health of your plants; root rot being one such problem requiring prompt attention. One such problem is root rot, which can cause significant damage if not addressed promptly. In this part, we'll look into how to detect indications of root rot in cannabis plants so you can act before it's too late.

Symptoms of Root Rot

Root rot affects the roots of your cannabis plant, preventing them from absorbing nutrients and water properly. This leads to several visible symptoms on the plant itself:

  • Wilting leaves: The leaves may start drooping or curling due to lack of water absorption.
  • Yellowing foliage: A deficiency in nutrients will cause the leaves to turn yellow or exhibit other discoloration patterns.
  • Rotten odor: As the roots decay, they emit a foul smell that becomes more noticeable as time goes on.
  • Brown and slimy roots: Healthy roots should be white and firm; however, when affected by root rot, they become brownish-black with a slimy texture.

Detecting Root Rot Early On

To catch root rot early enough for effective treatment measures, regularly inspect your cannabis plants' overall health. Pay close attention to any changes in leaf coloration or wilting patterns that might indicate an issue with nutrient uptake, especially if there are unpleasant odors emanating from around its base. By staying vigilant and monitoring your plants closely, you can identify root rot early on and take the necessary steps to treat it.

Factors That Contribute to Root Rot

Understanding the factors that contribute to root rot in cannabis plants is crucial for prevention and treatment. Some common causes include:

  • Poor drainage: Excess water around the roots creates a breeding ground for pathogens.
  • Overwatering: Providing too much water can lead to soggy soil conditions, promoting fungal growth.
  • Inadequate oxygenation of roots: Roots need oxygen to thrive; if they don't receive enough, they become more susceptible to disease.

In summary, being able to identify cannabis root rot is essential for maintaining healthy plants. Keep an eye out for symptoms such as wilting leaves, yellowing foliage, rotten odors, or brown slimy roots so you can address any issues promptly. Regularly inspect your plant's overall health and be aware of contributing factors like poor drainage or overwatering that could increase their risk of developing this damaging condition.

Causes of Cannabis Root Rot

Cannabis root rot is a common problem faced by growers, and it can be caused by various pathogens. Understanding the causes of root rot will help you prevent and treat this issue effectively. In this section, we'll discuss some of the main culprits behind cannabis root rot.

Fungi: Pythium and Fusarium

Pythium and Fusarium are two types of fungi that commonly cause root rot in cannabis plants. These fungi thrive in wet conditions with poor drainage, making overwatered plants particularly susceptible to infection.

  • Pythium: This fungus attacks the roots' outer layer, causing them to become slimy and discolored. As it progresses, Pythium can destroy entire sections of roots or even kill your plant if left untreated.
  • Fusarium: Fusarium targets the vascular system within your plant's roots, leading to wilting leaves as water uptake becomes restricted due to damaged tissue.

Bacteria: Pseudomonas spp., Erwinia spp., Ralstonia solanacearum

In addition to fungi like Pythium and Fusarium, certain bacteria can also lead to cannabis root rot issues:

  • Pseudomonas spp.: This group includes several species known for causing soft rots on a variety of crops, including cannabis. The roots can become soggy and take on an altered hue as a result of these bacteria.
  • Erwinia spp.: These bacteria are also responsible for soft rots in various plants. Like Pseudomonas, they can cause root decay by breaking down plant tissue and releasing enzymes that destroy cell walls.
  • Ralstonia solanacearum: This bacterium causes bacterial wilt disease in many plants, including cannabis. It invades the vascular system of roots, leading to wilting leaves as water uptake becomes restricted due to damaged tissue.

Poor Growing Conditions

Besides pathogens like fungi and bacteria, poor growing conditions can contribute significantly to root rot development in your cannabis plants:

  • Overwatering: Excessive watering creates a moist environment where harmful microorganisms thrive. This increases the chances of your plant developing root rot.
  • Inadequate Drainage: Poor drainage leads to standing water around your plant's roots which provides an ideal breeding ground for fungi and bacteria that cause root rot.
  • Lack of Oxygen: Waterlogged soil deprives your plant's roots of oxygen needed for healthy growth; this weakens their defenses against infection from pathogens such as Pythium or Fusarium.

Root rot can be a serious issue for cannabis growers, so it's important to identify the causes and take preventative measures. Treating root rot is often more difficult than preventing it, but with proper knowledge of symptoms and treatments, successful recovery from this disease is possible.

Treating Cannabis Root Rot

When you suspect that your cannabis plants are suffering from root rot, it's crucial to act quickly and decisively. The longer the issue persists, the more damage it can cause to your plants. Here are some effective methods for treating root rot in cannabis plants:

1. Remove Affected Roots

The first step in treating root rot is to carefully remove any affected roots from the plant. This will help prevent the spread of pathogens and give healthy roots a chance to recover. Use clean, sharp scissors or pruning shears to trim away discolored, mushy, or foul-smelling roots.

2. Clean Your Growing Medium

If you're growing cannabis in soil or another medium like coco coir, be sure to thoroughly clean and sterilize it before replanting your trimmed plant(s). You can do this by using hydrogen peroxide (H2O2) solution, which helps kill off harmful pathogens while also providing extra oxygen for healthier root growth.

3. Improve Drainage and Aeration

  • Aerate your soil: Loosen compacted soil around your cannabis plants by gently tilling with a fork or rake; this will improve drainage and allow air circulation around the roots.
  • Add perlite: Mixing perlite into your growing medium would increase its ability to drain excess water and prevent waterlogging.
  • Use fabric pots: Switching to fabric pots or air pots can improve drainage and aeration, reducing the risk of root rot in your cannabis plants.

4. Adjust Your Watering Schedule

Overwatering is one of the primary causes of root rot, so adjusting your watering schedule is crucial for treating and preventing this issue. Before irrigating again, allow the uppermost layer of soil to become arid; this will stimulate deeper root development while also averting an accumulation of moisture around the roots.

5. Introduce Beneficial Microbes

Add beneficial microbes like mycorrhizal fungi, which form symbiotic relationships with plant roots, aiding nutrient uptake and protecting against pathogens that cause root rot. You can find these helpful microorganisms in products such as Mykos or Great White at your local hydroponic store or online retailers.

Treating cannabis root rot may take some time and effort, but it's essential for ensuring healthy plants with optimal yields. By taking these steps, you can start to revive your afflicted cannabis plants and avoid any further episodes of this common issue.

Preventing Cannabis Root Rot

Preventing root rot in cannabis plants is essential to maintain a healthy and thriving garden. By following these tips, you can minimize the risk of encountering this issue:

  1. Maintain proper drainage: Ensure that your growing medium has adequate drainage to prevent waterlogging. Using well-draining soil mixes or adding perlite can help improve drainage. Additionally, make sure your pots have sufficient holes at the bottom for excess water to escape.
  2. Avoid overwatering: Overwatering is one of the main causes of root rot in cannabis plants. To avoid this problem, allow the top inch or two of soil to dry out before watering again. You can also utilize a hygrometer to ascertain whether it's the opportune moment for another watering session.
  3. Maintain optimal temperature and humidity levels: High temperatures and humidity create an ideal environment for pathogens causing root rot. Maintain temperatures between 68-77°F (20-25°C) and relative humidity at 40-60% during vegetative growth, reducing it slightly for flowering stages.
  4. Sterilize equipment regularly: Cleanliness is crucial when dealing with any plant disease; therefore, ensure all gardening tools are sterilized after each use. 
  5. Add beneficial microbes: Incorporating beneficial bacteria like Bacillus subtilis into your growing medium will protect against harmful pathogens by colonizing roots and creating a barrier against infection.
  6. Use proper air circulation: Adequate airflow is essential for preventing root rot. Make sure your grow room has sufficient ventilation and use oscillating fans to maintain consistent air movement. 

By implementing these preventative measures, you can significantly reduce the risk of cannabis root rot and ensure a successful harvest.

Checking Soil pH Level

One of the key factors in diagnosing and treating root rot in cannabis plants is checking the soil pH level. The optimal pH range for cannabis plants to absorb nutrients and stay healthy is between 6.0 and 7.0. When the soil's pH is outside of its preferred range, it can create a habitat conducive to harmful organisms that lead to root rot.

How to Check Soil pH Level

  1. Purchase a reliable pH meter: To accurately measure your soil's pH level, invest in a high-quality pH meter or test kit. These are available at most gardening stores or online retailers.
  2. Gather a sample of your soil: Using a clean trowel or spoon, collect some soil from around your cannabis plant's roots without disturbing them too much.
  3. Analyze the sample: Follow the instructions provided with your chosen testing method (either using a digital meter or chemical test) to determine the current acidity/alkalinity levels of your growing medium.
  4. Note down results: Record these measurements so you can track any changes over time and make adjustments as needed.

Maintaining Optimal Soil pH Levels

If you find that your cannabis plant's growing medium has an imbalanced pH level outside of its preferred range (6.0-7.0), take steps to correct it immediately by following these guidelines:

  • To increase alkalinity: Add dolomite lime or wood ash gradually until desired pH levels are reached.
  • To decrease alkalinity: Incorporate sulfur, aluminum sulfate, or citric acid into the soil to lower its pH value.

Remember that adjusting your soil's pH level should be done gradually and in small increments. Overcorrecting can cause additional stress on your cannabis plants and exacerbate root rot issues. Be sure to retest the soil after each adjustment to ensure you're moving closer to the optimal range without overshooting it.

In addition to maintaining proper pH levels, consider using a well-draining growing medium like coco coir or perlite mixed with potting soil. This will help prevent overwatering and promote healthy root growth while reducing the risk of developing root rot in your cannabis plants.

Reducing Water Frequency

One of the most effective ways to prevent and treat root rot in cannabis plants is by reducing water frequency. Overwatering your plants can create a breeding ground for pathogens that cause root rot, as they thrive in damp, oxygen-deprived environments. By ensuring that you're not overwatering your cannabis plants, you can help maintain healthy roots and avoid the development of this damaging condition.

Signs of Overwatered Cannabis Plants

  • Yellow leaves: When cannabis plants receive too much water, their leaves may turn yellow due to a lack of oxygen reaching the roots.
  • Drooping or wilting: Despite being well-watered, overwatered plants will often droop or wilt because their roots are struggling to absorb nutrients properly.
  • Mold or mildew growth: Excess moisture creates an ideal environment for mold and mildew growth on plant surfaces and within the soil itself.

If drooping or wilting, as well as mold and mildew growth are observed in cannabis plants, it is time to adjust the watering schedule. To determine when it's appropriate to water your plants again after noticing these symptoms, stick a finger about two inches into the soil; if it feels dry at that depth, then it's safe to proceed with watering.

Tips for Reducing Water Frequency

  1. Create a consistent watering schedule: Establishing a regular routine helps ensure that you don't accidentally over- or underwater your cannabis plants. Keep track of how often you're watering them so adjustments can be made as needed based on plant health indicators like leaf coloration and overall vigor.
  2. Use well-draining soil: Soil that drains properly prevents water from pooling around the roots, which can lead to root rot. A mixture of coco coir and perlite is an excellent choice for promoting good drainage in your cannabis plants.
  3. Monitor humidity levels: High humidity can contribute to overwatering issues by preventing moisture from evaporating as quickly as it should. Maintain relative humidity between 40-60% during vegetative growth and around 45% during flowering stages to minimize the risk of root rot development. Invest in a reliable hygrometer to keep track of these levels accurately.

Incorporating these practices into your cannabis cultivation routine will help you maintain healthy, strong roots while minimizing the likelihood of encountering root rot problems down the line.

Using Beneficial Bacteria and Fungicides

If you've identified root rot in your cannabis plants, it's time to take action by introducing beneficial bacteria and fungicides. These treatments can help restore the health of your plant's roots while preventing further damage from pathogens.

Beneficial Bacteria

Beneficial bacteria, such as Bacillus subtilis, are microorganisms that naturally occur in soil and promote healthy root growth. They work by competing with harmful fungi and bacteria for resources, ultimately inhibiting their growth. By adding these helpful microbes to your growing medium or hydroponic system, you can improve nutrient uptake and overall plant health.

  • Mycorrhizal inoculants: Mycorrhizae are symbiotic relationships between certain types of fungi and plant roots. The fungi increase nutrient absorption capabilities while receiving sugars produced by the plant through photosynthesis. You can purchase mycorrhizal inoculants at gardening stores or online to introduce these beneficial organisms into your grow setup.
  • Bacterial supplements: There are various bacterial supplements available on the market specifically designed for treating root rot in cannabis plants. Look for products containing strains like Bacillus subtilis or Pseudomonas fluorescens when shopping around.


In addition to beneficial bacteria, using a fungicide treatment may be necessary if the infection is severe enough. When selecting a fungicide product, opt for those labeled as safe for use on cannabis plants and follow the manufacturer's instructions carefully. Some popular fungicides include:

  • Hydrogen peroxide (H2O2): A common household item, hydrogen peroxide can be used as a mild fungicide to treat root rot in hydroponic systems. Mix a solution of one part hydrogen peroxide with three parts water and apply it directly to the roots for treating root rot.
  • Copper-based fungicides: Copper is known for its antifungal properties, making copper-based products an effective option for treating fungal infections like root rot. However, use caution when applying these products as excessive amounts can harm your plants.

Treating root rot effectively requires persistence and patience. By introducing beneficial bacteria and using appropriate fungicides, you'll give your cannabis plants the best chance at recovery while preventing future outbreaks.

Frequently Asked Questions How to Deal With Cannabis Root Rot

Can cannabis plants recover from root rot?

Yes, cannabis plants can recover from root rot if treated promptly and effectively. Early detection is crucial for successful treatment. Implementing proper watering practices, maintaining optimal pH levels, and using beneficial bacteria or fungicides can help restore the plant's health.

Does hydrogen peroxide help with cannabis root rot?

Hydrogen peroxide can be effective in treating cannabis root rot by adding oxygen to the water and killing harmful pathogens. A solution of 1 part 3% hydrogen peroxide to 4 parts water should be used when watering affected plants. However, it's essential to address underlying issues like overwatering or poor drainage as well.

What does root rot look like on cannabis?

Root rot on cannabis appears as brownish-black, slimy roots that are soft to touch instead of healthy white roots with a firm texture. The leaves may show signs of yellowing or wilting due to reduced nutrient uptake caused by damaged roots.

What causes cannabis root rot?

Cannabis root rot is primarily caused by overwatering and poor drainage leading to stagnant water around the roots which encourages fungal growth such as Pythium spp., Fusarium spp., and Rhizoctonia solani. Other factors include low oxygen levels in soil, high temperatures, excessive nutrients concentration, contaminated growing media or tools.


In this article, we have discussed how to identify root rot in cannabis plants, its causes, treatment options such as reducing water frequency and using beneficial bacteria and fungicides. Additionally, we have covered some preventative measures like checking soil pH levels. The key is not too water too often, and act quick as soon as you spot signs of cannabis root rot.