White mold grows on a cannabis bud, by OlegMalyshev via iStock

Moldy weed – A phrase nobody likes to hear. Our guide on how to prevent cannabis mold will help keep your bud fresh and fungus-free.

What To Do About Moldy Weed

High There

By High There

December 16, 2021

Mold. Just the word itself rolls off the tongue unpleasantly, but nobody wants to hear it in combination with their cannabis stash. Some people might insist on smoking moldy weed anyway, but as we’ll talk about below that can lead to health issues and an unpleasant experience (to say the least).

Keeping your cannabis products stored properly is an important part of the battle, but not everything. Keep reading for more on the signs of moldy weed, how to stop it, and the health problems it can lead to. With our tips and tricks, you’ll be able to keep your stash fresher for longer – Let’s jump in.

A collection of cannabis buds, by Social Butterfly MMG via Pixabay
Pictured: Fungus-free cannabis.

What Is Moldy Weed?

“Moldy weed” is cannabis that has been contaminated by mold or mildew. This normally happens in storage if the airtight containers are loose and the ambient humidity levels are too high; it can also happen in overly moist environments like a fridge or a freezer.

Moldy weed looks like a grey or white bud rot and smells like musty hay; smoking it can lead to health issues like coughing and breathing.

How Can You Recognize When Your Weed Has Gone Moldy?

It’s always a good idea to carefully check your weed before you smoke it; this is even more important if your weed has been stored away for a month or two, even if you have stored it correctly there’s a chance that the organic material has developed mold spores.

Let’s be blunt: If you identify mold on your weed, it’s best not to smoke it at all. Instead, cut your losses and throw out the whole batch. It can be tempting to cut off the bits of mold and use parts that appear to be untouched; the trouble is that mold spores spray in all directions, meaning chances are the batch is unusable.


Take out your weed and examine it; you can use your naked eye to look at the cannabis trichomes closely, or use a magnifying glass to get truly up-close. With healthy weed, the trichomes – tiny hairs that grow out from the epidermis of the plant – should glitter and sparkle; if the surface is grey and powdery instead, you likely have some mold.

Unless you are a discerning botanist, it can be easy to misconstrue this grayish white coating as part of cannabis plants, even a sign of quality: on the contrary (and as we’ll explain below) mold can be harmful.

Again, don’t be tempted to cut off the dark spots and bits of mold and smoke the weed anyway; there’s a high chance it won’t taste or smell the way you expect. In the best case, you’ll still feel it’s effects but won’t have a pleasant tasting or smelling experience. In the worst case, it could cause a serious allergic reaction, potentially landing you in hospital.


After you’ve carried out a visual examination of the weed, it’s time to give it a sniff. If you think the grey or white surface of the cannabis plant is a sign of quality, the smell test should persuade you otherwise – weed that’s been affected by mold has a very unpleasant aroma, a distinct odor from the usual skunky/sharp tones of cannabis.

Instead of the sweet aroma of fresh, healthy weed, what you have instead is a musty hay smell or the pungency of urea – definitely not something you’d want to smoke! Having said that, some cannabis users will persevere with their product even if they get a hint of off-ness from the weed.

With the visual and smell tests combined, this should be enough to help you determine if your batch of weed is contaminated and in need of disposal. 

Smoking contaminated weed will only lead to a poor experience at best and ill-health at worst. Proper storage can and will go a long way to extending the expiration date of almost any cannabis product, and helping avoid fungal infection.

A moldy cannabis plant, by Michael Nosek via iStock
Though this cannabis plant may look healthily crystal-covered on first glance….
A moldy cannabis plant, by Michael Nosek via iStock
… a quick look up-close reveals the tale-tale thin, web-like strands of a fungal infection.

Potential Health Hazards of Smoking Moldy Weed


When mold gets into your throat and lungs, it can be unpleasant and cause you to cough unexpectedly. While coughing as a result of smoking moldy weed is not be dangerous – unless you are allergic to the mold, of course – it is generally considered unwelcome.

If you have an allergic reaction, contact a medical professional; otherwise, the best response is to drink some water and – again – dispose of the entire batch of moldy weed.

Nausea and Vomiting

As you know, weed can make you lightheaded and euphoric thanks to THC content in the bud; however, these effects can be tainted by the presence of fungus spores in the weed, potentially leaving yourself feeling nauseous and queasy after smoking.

Again, these effects are not serious health hazards unless you have an allergic reaction to bud rot, in that case you will need to contact a health professional.

Lung Irritation

Inhaling foreign particles will always cause some degree of lung irritation, even if you’re only vaporizing weed and not, say, smoking tobacco. That said, weed affected by fungus spores can cause more irritation than usual and lead to serious lung or fungal infections – Inhaling mold is definitely a way to end up with serious medical complications.

More Serious Symptoms If You’re Allergic to Mold

The symptoms outlined above are non-serious health consequences of smoking moldy weed, but when someone has an allergy to said mold, the situation becomes more hazardous.

An allergic reaction to fungus spores can cause itchy eyes, sneezing, coughing, and restricted breathing in more serious cases. Be aware of how you respond to any cannabis product, and don’t be afraid to contact professionals.

What Causes Moldy Cannabis?

Mold is a fungus that develops in moist and humid locations; it’s a multicellular fungus that sprays reproductive spores that expand its sphere of influence. Unfortunately, cannabis is not immune to the influence of fungus; unless it is stored correctly and used in a time frame, it might go bad due to mold.

Mold thrives in moist environments that contain organic matter putting your cannabis in the high-risk category. If there is too much humidity in the room and the weed is exposed, it creates the conditions for moldy cannabis, which is why you need to seal it in a nut-jug and keep it in the dark.

A weed bud in the hand, by Cambridge Jenkins IV via unsplash
An example of a cannabis bud without mold – Note how the natural crystals of the plant can give the appearance of mold, often necessitating a smell test.

How to Prevent Your Weed from Developing Mold

To prevent your weed from developing fungus, buy quality product from a known and trusted source and store it correctly. This seems simple enough, but there are a few important things to know about weed storage first.

For weed to smoke properly, it needs to have moisture to stop it from drying out. Too much moisture, however, and you’ll end up with moldy weed. Much like preserving the freshness of high-end cigars, moisture and overall humidity should be controlled as primary ways to prevent mold.

Though we go into greater detail in our article “

“, the short version is:

To prevent your weed from developing harmful, mycotoxin-bearing fungus spores, place it in a tightly-sealed container and store it in a dark, dry place such as a cupboard or a drawer. Storing your weed like this helps to seal in the herb’s natural moisture, while also preventing humidity from seeping in from the outside.


Can I Scrape the Mold off My Weed?

If you had some weed stored away that you were looking forward to smoking, it can be a massive disappointment to discover that it has some mold on it.

As we’ve mentioned before, it can be tempting in situations like this to simply cut off the moldy portion of the weed and just carry on enjoying smoking moldy marijuana as you otherwise normally would.

Although possible, this strategy is not recommended; when mold appears on one part of the weed, its spores spread quickly to other parts, invisibly contaminating the whole. The weed might appear to be relatively unaffected, but you’ll still get an unpleasant musty smell when burned (and we assure you, that won’t get any better as it’s being inhaled).

How Long Does It Take for Cannabis to Go Moldy?

In general, weed can last for a minimum for up to six months when stored correctly. Correct storage of weed means keeping it in an airtight container in a dark, dry location; never store your weed in the refrigerator or anywhere that might promote mold growth. Solid, air-tight containers, in a dark, cool, non-humid area will always be your best bet.

It isn’t easy to provide a definitive answer to the question of how long it takes moldy marijuana to develop; it largely depends on the quality of the weed and the storage conditions. Weed that’s stored in humid places with little or no airflow tends to grow mold much faster.

What Should I Do If I Smoked Moldy Weed?

Moldy weed can be harmful if you have an underlying condition or are allergic to certain forms of mold; for this reason, it’s important to check your weed before smoking it. Even if there is little change in its appearance, always check to see if your weed is mold free by giving it a quick smell test – Inhaling mold will smell similarly to a musty basement or wet towel.

If you smoke moldy weed, it won’t taste or smell the way it should. Instead of sweet-smelling, it will smell like rotten hay. Most people won’t have any serious side effects from smoking moldy weed, with nausea, sinus pain and coughing typically being the worst.

However, side effects such as shortness of breath, chest pain, headaches, and dizziness could be signs of a serious lung infection or allergic attack, necessitating a visit to your local health care professional. Overall, we would say that it’s better not to take the risk, and avoid smoking moldy weed altogether. 

High There

About The Author

High There