what does moldy weed look like

How to identify and avoid buying moldy weed

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  1. What is mold?
  2. What happens if you smoke moldy weed?
  3. How to check for moldy weed
  4. How to keep your cannabis mold-free

Mold is never a welcome sight. Not in bread or cheese, and certainly not in your cannabis. Moldy weed is not only disgusting, it’s dangerous. Consuming mold-infested weed can have some serious adverse effects. But how do you know if your bud’s been infected?

Nearly every legal state has some sort of microbial lab testing requirement for regulated cannabis sales. These tests check for mold and mildew in batches of marijuana. However, even legal markets have seen their share of moldy cannabis over the years.

Read on to learn how to identify and avoid buying moldy weed and how to store weed so it doesn’t get moldy.

What is mold?

Mold is a catchall term for fungus that reproduces via lightweight, airborne spores. Humans inhale or ingest minuscule amounts of mold every day. It is typically harmless in small quantities since a healthy immune system can successfully prevent any damage.

Mold found on marijuana buds, or flower, is the same kind that grows on other plants. Botrytis (responsible for bud rot ), Mucor, Cladosporium, Rhizopus, and Penicillium (the mold responsible for penicillin) are the most common. Mold thrives in humid or moist environments that lack proper air ventilation.

Mold found on marijuana buds, or flower, is the same kind that grows on other plants. Photo by: Gina Coleman/Weedmaps

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In cannabis mold most often develops when the bud isn’t dried correctly, though it can form in earlier stages of cultivation, such as in a too-humid grow room. Improperly dried weed stored in an airtight container for curing creates an ideal breeding ground for mold.

Mold spores are tricky to eliminate. They can survive the intense heat of a lighter when smoking a hit and they don’t burn off in the oven when weed is decarbed. Some molds produce mycotoxins too, which can be carcinogenic.

What happens if you smoke moldy weed?

When you smoke moldy weed, you inhale the fungus directly into your lungs. Those with compromised immune systems are at risk of developing a lung infection. Smoking moldy weed is also dangerous for those with allergies to mold-based antibiotics such as penicillin.

A study published in “ Clinical Microbiology and Infection” 2017 found molds such as Aspergillus, Mucor, and other potentially harmful fungi in cannabis samples procured from northern California dispensaries. By smoking moldy weed medical marijuana patients risk fungal infections and other problems.

The bottom line is moldy weed cannot be made fit for use once contaminated. Always throw away moldy weed, even if your risk for infection is low.

How to check for moldy weed

Thankfully, there are several ways to determine if your flower is mold-free.

Use the naked eye method

Eyeballing your weed is by far the easiest way to check for mold.

Healthy cannabis should be covered in spindly, glittering trichomes. Trichomes are sparkly glands with tiny hairs that appear almost crystalline in structure, separated by distinct trichome nodules with space in between them.

These are significant signs to keep in mind as you visually examine your bud.

Some mold looks like cobwebs in the bud, leaving behind a cotton candy-like webbing that’s gray or white in appearance. This could also be caused by spider mites, but you don’t want to smoke bug-infested weed either.

Another type of mold looks suspiciously like kief but is far from the real thing. Powdery mildew is a form of fungus that leaves a gray or white powder-like appearance. It is usually dull and muted in color, and looks like dust compared to the sparkle of trichomes or kief.

Other mold signs are dark spots, gray or yellow fuzz, or a slimy residue. If you find mildew in your marijuana, quickly dispose of it and check the facility or container where it was stored to make sure it hasn’t spread to other buds.

Use your nose

The countless terpene combinations in cannabis present a wide array of aromas, from dank to exotic fruit to skunk. Moldy weed, however, has a very distinct and unpleasant aroma. Moldy marijuana smells like human sweat, urine, or musty hay, all of which are typically repulsive to the human nose. A quick whiff should tell you whether your weed’s been infected with mildew.

Moldy weed has a very distinct and unpleasant aroma. Photo by: Gina Coleman/Weedmaps

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Sniffing isn’t foolproof, however. Some people are more sensitive to cannabis’ aromatic nuances than others, and some users who are allergic to mold may have a reaction if they sniff too closely. And some molds don’t produce a smell, especially infestations that have only just taken root.

Use tools to check for mold

Consumers can also detect mold in their weed using low-powered microscopes, many of which are cheaply available online. Under a lens, mold produces filaments that look nothing like bubbly trichomes. If it doesn’t look like weed, it might be mold.

Black lights also can help reveal mold spores in your bud. Most mold glows an eerie green when illuminated by a black light, making it easier to identify.

Review brand websites and media for recalls

The best way to protect yourself from smoking moldy bud is to purchase lab-tested cannabis from a licensed dispensary. However, the legal marijuana market is expanding more rapidly than testing facilities and regulations can keep up with. And where legal restrictions still exist, illicitly produced marijuana products can still contain residual pesticides, fungicides, and microbial substances.

Keep an eye on local media, brand websites, and state and city websites for recalls of particular batches of products to help you discover unfit bud.

How to keep your cannabis mold-free

Storage is of the utmost importance when it comes to keeping your bud free from mold. Marijuana exposed to improper temperature, light, humidity, and air risks mold development, but there are things you can do to extend your weed’s shelf life and health.

Storage is of the utmost importance when it comes to keeping your bud free from mold. Photo by: Gina Coleman/Weedmaps

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First, make sure your weed is properly dried and cured. Most professional cultivators should do this right, but when growing your own bud, it’s essential to allow the flowers to dry correctly . The process can take up to seven days and should be done with care in proper environmental conditions. Correctly dried weed will cure successfully, maintaining the perfect balance between dry enough to smoke and moist enough to preserve the terpenes and trichomes. .

Store your bud in a cool, dry place but not in the freezer or refrigerator. It’s too cold, and the exposure to moisture is potentially mold-inducing. The ideal storage temperature for your flower is just below 77 degrees Fahrenheit.

Keep buds in airtight containers made of dark-colored glass. Mason jars and the like limit air and humidity exposure that could encourage mold development. Many dispensaries sell containers precisely for this purpose.

Finally, cannabis requires precise humidity levels to maintain its dry-but-not-too-dry, smokeable goodness . The humidity in your storage jars should stay between 59% and 63% to keep things perfect. You can buy disposable humidity packs, such as Boveda packs, to add to your jars.

How to identify and avoid buying moldy weed Copy article link to clipboard. Link copied to clipboard. Contents What is mold? What happens if you smoke moldy weed? How to

The Dangers of Moldy Weed: Is Your Stash Compromised?

Molds are a vast subcategory of fungus, distinctly different from yeasts. Molds reproduce by producing asexual spores, and these microscoping spores enter our bodies all the time.

Miniscule amounts of most types of mold spores are safe for humans, as the immune system fights them off. Mold generally thrives in moist and unventilated conditions, and dry climates are much less affected in comparison to humid environments.

On weed, mold typically develops when moisture is too high during the drying process, but it can also be formed during other stages of cultivation. The so-called “moisture lock” happens when we store weed which hasn’t properly dried in an airtight container, and by doing so creating a perfect breeding ground for mold to develop.

Some types of mold possess naturally-occurring toxins (mycotoxins), and these molds are most detrimental for human health.

What happens if you smoke moldy weed

In regards to weed, molds feed on the cannabis plant, and a moldy weed plant is considered diseased. Mold spores cannot be incinerated by smoking or vaping, and mold poses the biggest threat for people with a compromised immune system.

Frequent symptoms include coughing, sore throat, runny nose, sneezing, headaches, heaviness of breath, diarrhea, vomiting, heart palpitations, and in more serious cases, fever and pneumonia.

People who are allergic to penicillin and other mold-derived antibiotics can also experience an allergic reaction.

Mold is the number one health hazard for cannabis users, and in the worst-case scenario a user can develop a lung infection, requiring immediate hospitalization.

If left untreated, an infection caused by mold can result in fungus balls growing in the lungs (aspergillomas), which is a condition that requires an urgent surgical procedure.

What does moldy weed look like

The best way to figure out if your weed is infected by mold is through visual inspection.

Depending on the exact type of mold, it can have many different appearances.

Some types of mold look appear like white, grey or black web-like stuff, closely resembling a spider’s web.

Web-like Mold

Powdery mildew resembles confectionary sugar or sawdust, and people tend to mistake this kind of mold for dusted kief, or even that the weed was laced.

Powdery Mildew

Other types of mold create a sludge-like or slime-like matter on weed, which can be brownish, yellowish, or white/grey.

Sludge/Slime Mold

Mold that looks like dark spots (black or dark green) can also infect both buds and leaves.

Some people also have issues differentiating trichomes from mold. Trichomes are tiny transparent mushroom-like outgrowths on the surface of weed, where both cannabinoids and terpenes are located.

The best way to differentiate trichomes from mold is that trichomes appear very crystalline in structure, while mold has a web-like or cotton candy-like structure.

Weed’s trichome nodules are also very singular (with distinct spaces between them), while mold is completely interconnected.

If mold has recently developed, it can be very difficult to spot it with a naked eye.

Digital microscopes are a great way to circumvent the shortcomings of your eye, and you can find very affordable options (30$

Another way to detect mold is by using a blacklight (UV-A). Mold has a recognizable green hue when it’s illuminated by a black light.

What does moldy weed smell like

Another method for determining if your weed is moldy is through the sense of smell.

Depending on the type, the smell of mold can be like urine, sweat, hay, cat-like, musty or stuffy.

For maximal certainty, it’s best to combine both visual and odor detection techniques together.

Tips for amateur growers

When growing weed, there are numerous things you should always do, and several you want to avoid. First of all, don’t use fruit peels as fertilizer, as they can introduce mold spores.

For additional security, try growing strains that are high in anti-fungal terpenes such as limonene, eucalyptol and trans-nerolidol. The presence of these terpenes makes cannabis plants increasingly resistant to mold.

If you’re growing in a closed environment, use fans to keep the level of fresh air optimal.

For outdoor growers, there are four aspects to consider:

  • Grow plants suited for your climate
  • Grow your weed in a moderately windy area
  • If your plants are covered in morning dew, give each of them a proper shake
  • Use an overhead tarp in case of rain

You should regularly save cuttings in case mold infects your crop.

Also, make sure that you’ve carefully trimmed your buds before you start the drying process, as they retain less moisture. Desiccants are also a fine option when you’re packing your cannabis.

If mold happens, make sure to dispose of the infected plants immediately, in order to prevent further contamination. You should apply anti-mold agents to sanitize your grow room.


It’s important to understand that mold poses a very serious health risk, and reputable cannabis growers take it extremely seriously.

There were several big recalls because of mold in 2019, most notably in Michigan (48 pounds), Ontario (55 pounds), and Colorado (an undisclosed quantity).

If you’re legally acquiring cannabis, make sure to check the local media for recent recalls, even though it may seem somewhat dorky.

If you’re a frequent user always try to remain vigilant, because moldy weed is nothing to joke around with.

Moldy weed can be toxic if consumed. Use this guide to diagnose your buds and stay completely risk-free.