Identifying Cannabis Molds in Your Garden

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It is a fact that moldy weed is one of the most dangerous yet common nuisances in a cannabis garden. When left unchecked, the presence of molds can be extremely dangerous to your plants. And while they are already dangerous in themselves, the adverse properties of moldy weed can cause a more serious and detrimental health conditions to your weed crop. 

But despite it being a frequent visitor in your marijuana buds, moldy weed isn’t exactly the easiest thing to identify. In fact, without the sufficient knowledge about it, you may very well miss it completely! So, what exactly does moldy weed look like? And what should growers do in order to cure and prevent molds from developing?


What are the Earliest Signs of Moldy Weed?

It is important for you to be able to distinguish molds from, let’s say, the sticky trichomes in a cannabis bud. What may appear as a thin layer of dust may actually already be molds eating away on your cannabis leaves! An even more dangerous concern for growers is that the early symptoms of moldy weed are quite similar to other common diseases!

Here are some of the early signs that may indicate your plants contracting some moldy weed:

  • Subtle gray coatings in the leaves and buds of your plants
  • Powdery substance layering the leaves
  • Sometimes, you will notice spiderweb-like clouds sticking to your buds
  • Patches of yellow and/or dark brown around the stems and leaves
  • Discoloration of the plant
  • Roots and branches feeling mushy and fragile
  • Earthy and musky scent

As you can see, you will definitely have a lot of telltale signs to base your warning signs off of. However, these are symptoms that may indicate other conditions such as nutrient deficiency, watering problems, or pest infestations. This is why you will have to be a lot more detailed when it comes to mold identification.

Different Kinds of Molds in Marijuana

It may seem very unfortunate but there are actually different kinds of moldy weed that could infect your gardens. While each of these will look quite different and will impact your cannabis crops in different ways, they are all equally as damaging. 

Here are the most common molds that can turn your delectable and luscious buds into moldy weed:

Bud Rot (Botrytis Cinerea)

Bud rot is a type of mold that is generally considered as being exclusive to cannabis plants. As the name suggests, it is characterized by damaging the marijuana buds and rotting from the inside out. 

It is especially damaging because once bud  rot fully matures, there really is no curing it. As a result, growers will have no choice but to discard the whole plant carrying the moldy weed.


The first appearance of bud rot starts off as a white and cloudy substance. Over time, this develops into a much more dark and almost black sludge. It will feel very mushy and damp, as this is the stage that renders your buds completely useless.

How does it affect the buds?

Bud rot will usually start manifesting itself at the base of your cannabis plants. As it starts developing at the roots, it slowly makes its way into the plant’s stems until it begins entering your beautiful and precious flowers. 

Because of the dense foliage of leaves that will typically come with marijuana plants, it might be hard to detect the first signs of bud rot! They may very well keep themselves tucked into the bases of the cannabis plants where growers won’t think to look.

Once the bud rot starts to mature, it will literally start rotting from the core of your buds. Breaking them open, you will see a black mess inside your buds which will ultimately make them unfit for consumption.

Don’t Let it Spread

Despite bud rot being found in the buds, it still has the tendency to spread all over your cannabis gardens. If you are not careful, the pores and bacteria of botrytis will find ways to enter your plants via cracks and damages. 

The only way to treat your cannabis plants which are infected with bud rot is by cutting them off and discarding any infected part of the gardens. Your buds will be pretty much useless once they are contaminated with bud rot so it is better to stop the spread by quickly removing any part that it already destroys.

Powdery Mildew

On the other end, we have powdery mildew. This is another form of molds that is generally a lot easier to spot and treat than bud rot. However, it is nowhere near as forgiving because powdery mildew can also significantly deter the growth and development of healthy buds in the cannabis gardens. 

Powdery mildew has the tendency to multiply quickly and spread itself among the other surrounding plants if left unchecked. It thrives in humid environments where there is no oxygen and airflow to keep the plants active. A stagnant growing environment allows the powdery mildew to set itself upon the leaves without anything to push it away.


Powdery mildew will, in fact, look like a layer of powder or a coating of sugar that usually spreads itself across the leaves and buds. During its early stages, powdery mildew might come across some as trichomes that set themselves upon the sugar leaves of the cannabis plant.

However, as they start spreading in wide volumes, they will look more and more like a dry, chalky substance that gets thicker and thicker.

How does it affect the cannabis plants?

Powdery mildew will prefer sheltering themselves upon broad and wide leaves. This means that mature and fully developed cannabis plants are much more susceptible to the development of powdery mildew. 

Because this type of mold produces a layer of its  substance on top of the leaves, the cannabis plants will have a harder time absorbing spectrums of light. This, in turn, will lead to the cannabis plants not being able to photosynthesize properly. 

Without the ability to properly absorb light, the cannabis plants will not have the ample amounts of energy to continue the development of healthy and potent weed buds. Additionally, the quick spread of powdery mildew will also prove to be a hassle to get rid of! 

Killing Molds

If you do have them in your gardens, simply take some water and carefully rinse off any powdery mildew form the leaves. Make sure to place a bucket or towel underneath that catches all the molds. Leaving them to fall on the ground will simply cause them to make their way back to the leaves. 

Neem oil is also a great alternative that kills the molds once it is sprayed onto the leaves. Make sure to purchase or make an organic solution that does not damage your plants.

Main Factors That Affect Mold Development

Perhaps one of the good things to learn about molds is that it will take a very uncontrolled and untidy environment in order for them to grow and thrive in. Keeping the conditions and climates of your gardens in check won’t give moldy weed the opportunity to contaminate your gardens! 

But what exactly should you keep in mind when regulating your gardens? What conditions will help you keep moldy weed away?

  • Temperatures – Almost every disease and illness in a cannabis plant will depend on the temperatures and mold development is no exception. Molds will typically flourish in warm and stagnant environments with temperatures of 80 degrees Fahrenheit. On the other hand, a colder environment will also cause dampness and moisture that invites molds. A temperature of around 65 degrees Fahrenheit may cause this. As such, it is important to strike the perfect balance between hotness and coldness in temperature! Try keeping your area at a good 72 to 75 degrees for the best results. 
  • Air flow – A constant flow and circulation of air helps keep the cannabis plants fresh and healthy. Without it, the area would prove to be too humid which can cause the growth and development of bud rot. As such, it is crucial to keep the steady air flow in your gardens as this could also prevent powdery mildew from settling in your leaves.
  • Lighting – A dark and dim place often invites molds to stimulate their systems and send their pores into the cannabis gardens. Because weed gardens will inherently need long hours of darkness, make sure you stick to a strict and precise lighting schedule! The alternate environments will also help slow down any moldy weed in your crops. 
  • Watering – Perhaps the biggest factor in having moldy weed is the dampness and moisture in the growing area! This comes mainly from the watering of plants where the growing medium tends to hold excess amounts of water. In fact, all types of mold will require a certain degree of moisture and dampness in order to thrive. Keeping the water levels of your plants regulated will give it a much lesser chance of moldy weed.


When does mold usually develop?

The thing about molds is that they do not choose any time to manifest themselves. As long as they are given the right conditions to grow in, moldy weed can definitely find a way into your cannabis plant’s buds, stems, leaves, and roots. As your plants start their vegetative stage, all their energies are placed into the development of stems, branches, and of course, leaves. And you know what likes sheltering themselves on leaves? Powdery mildew.

Because powdery mildew prevents the absorption of light, this is extremely detrimental to the vegging phase. Your plants will need around 18 to 24 hours of light for this stage in their lives. The presence of molds will definitely hinder them from achieving this.

Cannabis and Stages

When we get to the flowering stages, the buds of the cannabis plant start forming. This gives bud rot an opportunity to establish themselves at the base of your gardens and make their way into the buds’ core. 

If you think that things stop there, then you are wrong! Molds and mildew still pose a threat during the drying, curing, and even storing stages of weed! Anywhere that may have moist, dark, and humid places will carry the risk of having bud rot and bacteria form around your weed stash.  

How to Cure and Prevent Moldy Weed

Whether you choose to set up an indoor or outdoor garden, the fact still remains: moldy weed can happen! Here, we will enumerate some simple steps on how to properly prevent cannabis in both an indoor and outdoor grow.

Following these guidelines might not make your gardens 100% immune but it will definitely reduce the risk of moldy weed in your cannabis crops!

Prevent Moldy Weed Indoors

Using an indoor cannabis setup gives you the benefit of being able to control the climate of your grow room. As such, you can fully use this to your advantage and make sure that your weed crops grow under specific conditions! 

Make sure you have a thermostat that helps you keep track of the temperatures in your grow area. Keeping a dehumidifier or scattering some humidity packs in your gardens will also help keep a humidity level of ideally 30% to 50%. Also, make sure that there is a constant flow of air across the area. This is made possible through fans and air vents that allow a continuously moving circulation!

Pruning, Topping and Trimming

Of course, you should always keep your cannabis growing area neat and tidy. This applies not only to the growing area around it but also to the plants themselves! Clear away any fallen leaves, dried branches, or stray debris that could attract the build-up of molds and bacteria. Regular pruning, topping, and trimming will also keep the plants a lot more poised and well-groomed. Doing so will also lessen the congested spaces and allow growers to keep better track of their weed plants.

Make sure to place an ample amount of space in between your plants. Remember, molds tend to jump from one plant to another! You can also observe the base of your plants a lot easier.

Prevent Moldy Weed Outdoors

For obvious reasons, growing your cannabis plants outdoors will come with a lot more risk of moldy weed contaminating your precious cannabis babies. You will have a more limited opportunity to control the climates as well as having your plants more exposed to the outside elements. These elements will, of course, act as carriers of molds and bacteria. However, it is still possible to significantly trim down the possibility of molds in your outdoor setup! Here’s how:

Because they will be situated outdoors, it is important to keep your cannabis plants healthy and properly fed. This strengthens their immune systems and helps them prevent any molds from getting into their buds and stems. One key part of doing so is choosing an outdoor mold-resistant strain. Once you have those, half your work is done!

Light and Air

Do not place all your weed seeds tightly packed against one another. When they start to mature, the compact structures of the plants make it all the more easy for the moldy weed to spread across the gardens. Additionally, this also prevents the uneven distribution of light, nutrients, and water in the growing medium. Regular pruning and topping ensures the constant exposure of the leaves to light and air. 

And since you will be using an outdoor growing setup, it would be quite impossible to stop any rainfall or droughts from affecting your plants. One effective way of preventing too much moisture in your gardens is by placing heat packs above the overly wet soils. This seeps up the excess moisture which is an ideal shelter for weed.

Cleanliness is Key

Just like in an indoor setup, cleanliness is key to prevent moldy weed. Taking off any leaves and other stray trash in your growing area keeps the area clear of any unnecessary carriers and agents of molds and mildew.

Molds are undoubtedly in the upper echelon of a marijuana garden’s top contaminants. Despite them being hard to treat and remove once they take a hold of your plants, you can effectively prevent them by providing the right growing conditions and observing cleanliness!

Moldy weed and mildew are easy to spot as long as you know what and where to actually look! This article may serve as a guide for identifying moldy weed and what actions to take in order to prevent their development!

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