Moldy Weed: How To Detect It & Why It’s Dangerous

Mold can settle — sometimes with alarming speed — almost everywhere you look, as well as in even more places where you don’t. To date, scientists have identified over 100,000 different species of mold and mildew. They grow on your walls, on food left out to long, and outside. Some mold species are harmless, while others are even beneficial. Many, of course, pose a threat to human health. 

With mold being such a ubiquitous phenomenon, it’s only logical that good old cannabis isn’t exempt from its proliferation. Seasoned “canna-oisseurs” might know exactly what to look for, but the fact is that many newer cannabis enthusiasts do not. 

That matters, because — as you’ll discover in this guide — smoking or otherwise enjoying mold-infested cannabis can have some side effects. Some are mild and a mere nuisance, while others are quite dangerous. 

The bottom line? You don’t want to dabble in moldy weed. Here’s how you can make sure that your stash is safe, as well as what can happen if you don’t pay close attention and inadvertently inhale or eat moldy cannabis. 

inspecting cannabis

How to Gauge the Quality of Your Cannabis

If you’re after top-quality weed, you need to know what you’re looking for — and that’s true not just when you’re ordering cannabis from a legal dispensary, but also when you’re giving the stash you’ve forgotten about for a while a good once-over before enjoying it. 

To make sure your weed is in good condition, subject it to some informal quality control tests:

  • Even novice weed enthusiasts can easily subject their cannabis to the “color test”. Good weed comes in an abundance of green shades. More exotic strains will also contain purple, orange, gold, or even blue hues, but brown isn’t something you want to see. 
  • You will also want to look for beautiful, healthy, trichomes — small, shiny appendages that look somewhat like crystals. Trichomes may, to the uninitiated, resemble mold. They’re clear and glossy, however, much more toward the silver end of the color spectrum than the gray.
  • Give your weed a good whiff. It should smell like weed. If the smell has faded or your cannabis smells of something other than cannabis, you have a problem. 
  • Next up, you will want to examine the texture of your herbs. Crumbling dry weed is old and stale. Moist and humid weed is more likely to harbor mold, because those are the conditions under which mold thrives. You’re aiming for fresh and sticky.
  • Your final test — while you’re smoking your weed — would be to evaluate the experience. Does your weed taste bad, and are there hints of chemicals or a metallic taste? That’s not good. Do you cough excessively, and does your chest feel irritated, when compared to better weed? That’s another sign that something is amiss.

As the cannabis market is growing ever more competitive, the good news is that the overall quality of the product you can source from legal dispensaries is rising. You still have to have a keen eye, however, and especially if you haven’t kept your stash in a nifty and safe storage solution like a CVault, you will also have to evaluate your marijuana again before smoking or otherwise enjoying it.

how to detect moldy weed

How Cannabis Gets Moldy

Research has identified the fact that marijuana can be exposed to mold during the cultivation process. Interestingly, the mold species most likely to infest cannabis differ depending on the growth process — indoor weed is more likely to be exposed to Penicillium species, many of which are harmless and even helpful but some of which are dangerous to human health, while weed grown outdoors is more likely to  harbor Cladosporium molds, which are notorious for causing allergy symptoms like nasal blockages in people.

Many growers are reluctant to use pesticides, many of which can also fight mold spores, out of concern for the quality of their product and consumer safety. This does mean that your cannabis may be infested with mold spores from the moment you buy it — even if no clear signs were visible at the time. 

Should you store your weed improperly, in an environment where it is routinely exposed to relative humidity levels above 50 percent, new mold growth is also highly possible. You know the drill — just like storing apples in your grandmother’s humid basement would cause them to sprout moldy “hairs”, failing to look after your weed will expose it to possible mold growth. 

Mold, generally, thrives in literally any environment where it has access to water. Look into airtight storage solutions to protect your stash, because mold will take hold anywhere where there’s humidity and poor ventilation.

Common Types of Cannabis Mold and Rot

If you’ve ever seen moldy bread or a damp basement wall covered in black mold, you might think you’d easily be able to identify the presence of mold. With so many different mold species out there, however, it’s only logical that really don’t all look alike. 

Are you a novice cannabis enjoyer? It’s even possible that you won’t notice mold growth on your weed buds at all, and that you’ll instead think that’s what weed is meant to look like. Due to the risks associated with consuming moldy cannabis, it’s important to be able to tell what moldy cannabis — also often referred to as cannabis rot or bud rot — physically looks like. 

The fact that cannabis plants are vulnerable to diverse types of mold, with wildly varying physical appearances, makes identifying moldy weed more challenging. Knowledge is the only way to counter this obstacle, so here’s a look at the different types of cannabis mold and rot and their “symptoms”. 

Keep in mind that research regarding strains grown indoors alone has identified at least nine common types of cannabis mold. As an avid consumer, you will never be able to find out what specific mold species has (or have, because multiple can be present) has taken over your precious herb, but you can absolutely ascertain that cannabis mold or rot is present. 

example of mildew


The difference between mold and mildew is not that well established, and the Environmental Protection Agency (EPA) notes that people “generically” tend to refer to any mold with a “flat growth habit” as mildew. 

When you see this kind of fungal growth on your weed, of any strain, it will leave a light white powder-like coating on the buds and leaves. Your bud will have a white or gray layer that looks suspicious and may raise up into the air when you fumble with your stash. 

gray mold example

Gray Mold

Gray mold often indicates the presence of Botrytis species. This is the exact type of cannabis mold that’s most often called bud rot, and it’s insidious. Starting deep within the colas, gray mold may not be apparent at all when you first buy the cannabis. 

Appearing at the core of cannabis buds, the grower may not have been aware that gray mold was present at all. It spreads only gradually, over time — and before it spreads toward the outer parts of the plant, your herb may appear to be perfectly healthy. 

In the early stages of the proliferation of gray mold on your cannabis, gray mold will take on the appearance of a white, fuzzy, substance, which folks who are new to enjoying weed may easily take to be normal. Later in its developmental stages, gray mold on cannabis can turn weed a deeper gray, and even black. Left unchecked, your stash can eventually become “slimy”. 

white fuzzy mold example

White and Fuzzy Mold

This type of mold is more immediately recognizable as such — it resembles the kind of mold you might get on bread or an old apple that’s been left out in slightly warmer and more humid conditions. It has a white or light gray color, and a fuzzy or hairy appearance. 

Want to know more? Do wordy descriptions of moldy cannabis not quite cut it for you, and do you need visual information? Google is your friend — moldy cannabis, in all its menacing incarnations, can now be found freely on the world wide web, helping you enjoy your weed safely every time.

How to Detect Mold in Your Stash

Scared yet? Good — we want you to be able to enjoy premium-quality weed safely. Building mold-detection steps into your regular routine is a good idea if you have the same goal. 

We have already covered what mold can look like after it has infested cannabis. Moldy cannabis may be powdery and subtle, white, fuzzy, and characteristically mold-like in appearance, or dark gray and slimy. Do not take the quality of your weed for granted, but give it a good visual inspection. 

Your eyes are far from your only helpful sense when you’re trying to detect mold in your stash, however. Give it a smell. Do you detect a suspicious musty odor? In other words, does your weed smell like mold? You know what they say — where there’s smoke, there’s fire. Even if you don’t see any mold on your weed, it may be hiding deep within your bud.

Freshstor CVault review

How to Keep Your Cannabis Safe From Mold

We have already established that mold can take hold during any stage of the growth process. Dedicated and ethical commercial growers everywhere are always discussing ways to combat mold without the use of pesticides.

Some people specifically opt for more mold-resistant cannabis strains, and that’s something you can potentially benefit from as a consumer, as well. Sativa and hybrid strains are known to be more resistant to mold due to their terpene content.

You also have to do your part, however, to prevent your cannabis from turning moldy, and that includes:

  • Developing dedicated storage solutions for your stash. Airtight containers, for which aluminum and dark glass are a primary choice, are now on the market specifically to safeguard your cannabis from the environment outside — and to keep your stash fresh. Use them!
  • Do be mindful of the humidity levels you expose your cannabis to, but do not store your weed in your fridge because you’ve heard that marijuana likes to be kept in the dark. Your fridge provides a fairly humid environment, where your stash may also come into contact with other produce that already contains mold spores. Dedicated humidors like those from Cannaseur for example.
  • Source your cannabis from a reputable legal vendor. This decreases the risk that your weed will be moldy from the get-go.
  • Finally, always inspect your weed before using it. Mold happens. Yes, even astronauts found themselves combating mold when trying to grow crops in space. No matter how careful you are, mold may find a way. Therefore, use your eyes, your nose, and your sense of touch as you inspect your weed. Flower magnification devices like Smokus Focus jars are great for this, and just plain fun!

What if you do find mold in your weed? Some people suggest heating it to remove the mold, but although that may kill the spores, there is no evidence to suggest that makes the smoking experience any healthier. “Ditch it” is, unfortunately, the correct and safest approach.

health risks of moldy weed

What Are the Health Risks Associated with Consuming Moldy Weed?

The risks associated with mold exposure are far from unique to cannabis alone, so at this point we’d invite you to Google “health consequences of mold exposure”, or something similar. The general gist — the “too long; didn’t read” version — goes something like this. 

Most people experience something that amounts to mild irritation when they are exposed to mold. That irritation will stop soon after you leave a moldy environment. Over time, however, you become sensitized to mold, and risk developing a mold allergy. Then, when you come into contact with mold again, you will suffer much more severe and unpleasant reactions. 

When it comes to mold in your stash, on the other hand, you are not merely inhaling environmental mold spores. You are actively inviting them into your lungs, if you’re smoking weed. 

Especially if you are already allergic to mild, you can expect to be “rewarded” with lung irritation in the form of coughing and wheezing, sinus pain, and nasal congestion. As your body senses you’re putting something into it that you’re not meant to, you may also feel sick. 

In most cases, these reactions will merely be temporary — but do you really want to risk it?

HerbCEO Final Thoughts

Herb CEO Summary

At the end of the day the best frame of mind is to consume your herb at a fast pace. “No problem!” many of you may exclaim and we’d tend to agree. Cannabis is usually at its most potent and always most flavorful when it is fresh.

Mold is no joke, whether it is in your home, workplace, or stash jar. Mold is also a precarious thing, you can’t see the spores so getting rid of it once it’s developed can be a real chore, requiring sterilization of your equipment and storage containers.

Dry, cool places are best and always keep your precious nugs sealed in an airtight container and you shouldn’t have anything to worry about. If you DO find mold, especially on a recent purchase, bring it back to the dispensary you bought it from, the budtender might have missed it and you should be able to get a refund of some kind.


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