What You Should Know About Mold Issues on Marijuana

Posted in Plant Knowledge | By Spark Report |


It was recently reveled that police investigating Michael Jackson’s death had mistaken moldy marijuana for “tar heroin” following the pop stars death. While the moldy weed played no part in the investigation or Jackson’s death, it does bring up an often overlooked problem that faces almost every marijuana user, grower or distributor: Mold.

Anyone who has smoked marijuana more than a couple times has most likely inhaled mold spores from marijuana. That may sound alarming, however its important to remember that you are likely to inhale the same or similar mold spores while taking a walk in the park. The most common type of mold, Aspergillus, occurs naturally in almost everything in nature.

Most mold spores will have little effect on people with normal immune systems. If the mold is bad enough to cause problems, effects are usually respiratory breathing problems and flu like symptoms such as coughing, diarrhea and vomiting but can be more severe in people with other health conditions and/or a poor immune systems.

Causes of mold on marijuana

Mold issues in marijuana are almost always due to moisture lock. If marijuana is packaged or cured in air-tight containers while there is still a lot of moisture in the buds, it creates a perfect environment for mold to thrive in. While most growers and distributors take extra precautions in preventing mold, some will actually add moisture to properly dried marijuana in order to artificially increases the weight to increase profits.

In researching this article, I found some people will even bury their stash in hopes of encouraging a certain type of mold that is said to increase the potency of marijuana. This trend is highly discouraged due to the fact that it’s almost impossible to isolate that specific mold strain from other mold strains that will degrade and destroy the THC (active ingredient) in marijuana.

Identifying mold on marijuana

You can identify mold by looking closely for black spots, dark green spots, white/grayish stringy matter or other unusual coloring. The mold will also noticeably effect the smell of the marijuana, turning it a more musty and unpleasant smell. Mold spores sometimes resemble the crystal looking trichomes that naturally occur on marijuana which can cause some novice users to mistake signs of mold for characteristics of higher grade marijuana. The best way to identify mold on marijuana is to view it under a black light. Mold spores will appear a distinctive green hue when put under a black light.

Preventing / Treating mold on marijuana

Mold needs at least 15% moisture to survive, so the best way to prevent mold is to keep all harvested marijuana in the ideal 10%-15% moisture content level.  Growers should always allow enough time for freshly cut plants to dry in a dark ventilated area. Marijuana being cured in jars should be opened every 12 to 24 hours to allow proper air flow. Always be careful when attempting to re-hydrate over-dried buds by adding orange peels or water because it’s very easy to add too much moisture and fruit peels are an easy breeding ground for mold.

It’s always advisable to not smoke marijuana with mold, however those that are willing to take the risk are advised to bake their marijuana in a oven on 300 degrees for 15 minutes to eliminate some common forms of mold. While on the subject of baking marijuana, it is important to note that most mold is far more dangerous when ingested than inhaled, which means you should be extra careful of mold when putting marijuana into edible treats. Filtering smoke through a water pipe or bong does not prevent you from inhaling mold, although some sources say it can help reduce about 15% of the mold.

Although the exact moisture content is impossible to tell, by learning what to look for, consumers can prevent purchasing moldy marijuana and determine whether questionable buds should be smoked or thrown out. As marijuana becomes a more accepted form of medicine for seriously ill patients, mold education becomes even more important for care givers and government regulators to insure patients are protected due to them being more susceptible to the effects of mold than average recreational users.

photo by: Bistrosavage

Your Thoughts:

Discussion: 30 Responses

  1. Perry says:

    very good info! i would say all of this is 100% correct to my knowledge as a grower! stay safe and keep toking!

  2. bob says:

    300 degrees C or F????

  3. Dizzay says:


  4. VaporClaus says:

    “C or F”?
    No science student– or even a sci-fi fan– could make such a mistake:
    300 degrees Celsius would be 572 degrees Fahrenheit, and thanks to Ray Bradbury, we all know that the ignition point of paper is “Fahreneit 451″!
    So even if you DID have a pottery kiln which you sometimes used to heat up your TV dinners– the instant you exposed your pot to those temps, it would burst into flames!
    Of course, that WOULD eliminate your mold problem…

    I have discovered a better remedy than heat–
    That’s right: one of those cans you clean your keyboard with!
    And it will not only kill the mold– it will destroy the spores which are causing the odor!!!
    Best of all: when done properly, IT IS HARMLESS!

    From Wikipedia:
    Despite the name “canned air,” the cans actually contain gases that are much easier to compress into liquids, such as difluoroethane, trifluoroethane, or tetrafluoroethane. Hydrocarbons, like butane, were often used in the past, but their flammability forced manufacturers to use fluorocarbons….since gas dusters are one of the many inhalants that can be easily abused, many manufacturers have added a bittering agent to deter people from inhaling the product.

    The gas comes out of the can at about 20 DEGREES BELOW ZERO (that’s Fahrenheit, Bob)– and that blast of cold, dry air crystallizes the mold spores on contact. Plus, the fluorocarbons kill any remaining mold hiding deeper between the buds.

    Here’s how I did it when I discovered mold on an LB I left sealed up too long:
    I cut the moldy pot off the surface (saving it into a separate container), then busted up the rest of the chunks and placed them inside a large plastic coffee can. I then took my keyboard duster, inverted it and stuck the straw into a crack of the lid of the coffee can and gave a couple of one-second bursts. Open the lid, rotate the can slightly, and repeat; shake can to increase exposure, and repeat entire process.
    I then spread the entire mass into a porous container and let it air out overnight.

    LB saved…FOR ABOUT $5!!!

  5. Lil Bill says:

    HaHa let’s go vape our moldy weed before we smoke
    god so many people on here write dumb ass shit.

  6. ted says:

    How the hell are police going to mistake Black Tar Heroin for any kind of marijuana policemen we are talking about that’s just a cover up

  7. Peggi Munson says:

    My Son gorws ligally of course, although he brought his plants inside because of the rain and now after 2days he has what appears to be mold on the leaves and possibly on the buds. This must be thrown out? I dont know if u answer or not but would luv to know…

  8. Allegedly HIGH says:

    Where in the hell does it say Celsius?

  9. Jasom says:

    Do not listen to this fucking idiot above me, gas dusters contain a sticky substance used to make aerosol cans called CFC’s or flourocarbons. These can be deadly if inhaled and no doubt, should you spray weed with them, there will certainly be residue left behind. Bake at 300 for 5 min according to researchers.

  10. IncreaseThePeace says:

    Jasom provides a perfect example of the use of vitriol & aggression to disguise a pronounced lack of learning– which IMHO is the core source of America’s decline in the world. (Like teaching that “evolution is a theory– just like Creationism– except the FORMER is approved by GEEKS, and the LATTER is approved BY GOD!!”)
    When did we start letting morons pretend to participate in SCIENTIFIC DISCUSSIONS, just because they shout & throw a few “fucks” around?
    Jasom’s very argument displays his stupidity:
    Keyboard Dusters spray “STICKY STUFF”????
    It’s every bit as ludicrous as “Volcanos produce most CO2 in the atmosphere– NOT HUMANS” (BTW: Humans produce around 187 TIMES as much as volcanos— but as Jasom will surely tell you: “It makes sense– if you don’t THINK about it…)
    To ALL: what Vapor Claus states is one SCIENTIFIC RESULT; furthermore, he has described the process sufficiently to allow it to be reproduced– ANOTHER STEP IN THE SCIENTIFIC PROCESS; I can find nothing in the literature to refute him, so barring the conduct of his experiment myself, I must accept his results, pending further peer review.
    UNLIKE Jasom– who cannot grasp that his vulgar demeanor self-eliminates him from adult conversations ( post hoc, ergo propter hoc)

  11. VaporClaus says:

    Can you tell me why my reply to Jasom was deleted, while his insult to me remains public? If due to different email address, just tell me which one you have, and I will send you a message from it immediately…

  12. Mr.Mike63 says:

    Now getting down to the wire I discover yet another problem for the year. It was horrible that 4 out of five of my really beautiful plants turned out to be males and the last one was a worry all summer as the leaves turned a bright yellow and fell off. Now my last plant has some beautiful buds, I am finding this nasty mold on my plant. What to do? Most of the leaves are off leaving just thebuds (some up to 12″ long) looks kind of funny but smells like sweet melon and totally covered with trichomes. The rain of this year did not help and probably is the blame of the mold. we’re running 6 days in a row this storm.
    Can this mold just be cut out while still a whole plant, should I bring her down and cut out the mold and throw that away? The trichromes are not mature as of yet but I really don’t want to lose the little bit I babied all summer….any ideas? anyone?

  13. VaporClaus says:

    [2nd attempt to post this]
    Jasom seems to be exemplary of a class of persons whom I fear are all too quickly becoming the norm amongst wanna-be bloggers:
    Out of respect for the “researchers” to whom Jasom refers, I had previously elected to overlook one major flaw in their advice (to whom Jasom pledges allegiance)– to whit, this little gem from the official website for Volcano Vaporizers:
    “The active ingredient [THC] vaporizes when heated to between 338 F and 372 F”
    In other words, according to the world’s FOREMOST EXPERTS on the subject, following this advice and BAKING your pot at temperatures approaching that for so long would, in effect, BOIL AWAY THE ONLY INGREDIENT YOU WANTED IT FOR, IN THE FIRST PLACE.
    I have no reason to believe that theirs was anything other than an innocent error, based on giving priority to two lesser points: 1.) they assumed that pot is consumed by burning it, and that any process that stopped short of actual ignition would suffice, and 2.) they had to suggest a temp which would, in fact, kill the mold itself (although it might do nothing about the spores causing the odor).
    Their innocent error contrasts wildly with JASOM’S post—which was revelatory of BOTH his personal ignorance AND his lack of social skills. The former was demonstrated when he wrote:
    “gas dusters contain a sticky substance…called CFCs”
    Apparently Jasom’s in-depth research failed to discover that, beginning in 1987, CFCs have been phased out due to their depletive effect on the planet’s ozone layer– their manufacture & use ended in the industrialized world by 2000, and the entire third world by 2010.
    So, unless Jasom is getting antique containers of refrigerant from some black market source, his commentary is as useless, as my sainted grandpappy would say, “as tits on a boar hog”…
    And his lack of social skill was demonstrated by his fatuous use of vulgarity & insult—which simply self-identifies him as a cretin & a dolt– seemingly of the “Tea Party” variety…
    Not even a nice try, Jasom; just an embarrassing one…

  14. Smokie says:

    Well baking weed at 300 f cant be good considering the thc starts to vaporize at 215 degrees. Anyone that has made oil knows you cant heat weed to 300 F.

  15. chefdsal says:

    i know mold removers for homes and such use dry ice to kill mold. i just did a dry ice sift with a bubble bag and made kief or dry sift whatever youd like to call it. id have to say mold dead and all i have remaining is the kief. good for smoke or eat.

  16. AngelSperm says:

    THC boiling point is 157 °C
    you sure as fuck dont want to spray your buds with something you buy in a local hardware store.
    i dont know what you are being dumb about i just take out the mold and put a fan on it, you dont want to smoke the mold anyway, keep a close eye on the bud and if the shit comes back you’re going to have to throw it out anyway.
    BTW my plants where outside 24/7 in holland 2011, and this was the shittiest summer in 100 years, i have mold but not in the buds (some buds do have mold but thats the crappy plant) i just cut off the mold and hope it doesnt come back, i did see some dude on youtube spray his plants with special milk, but i wouldnt wanna smoke dairy at any point in my life AT ALL under whatever cercomestances but thats personal i guess

  17. twan says:

    omg are you serious? why the fuck would people inhale whole cans of that stuff daily and live if it was so “deadly” the canned air idea is actually not that bad of an idea. all fluorocarbons are gases and therefore would evaporate off of anything it came in contact with. That’s why it disappears when you spray it on your hand, and that’s why its IN A CAN. COMPRESSED. Because like many other substances, it cannot be held in one place in open air. IDIOT

  18. Kris says:

    If you have white mold on your plants you can do a peroxide bath on it when u harvest it. About a half a bottle ( a cup or so) of peroxide to 5 gallons of water.soak your plant for 5 mins or so. You should see the mold skin up the water surface. Scoop it off with a sponge before you remove the plant. Remove the plant through clean water surface.Shake out the water and then hang plant in front of a fan for an hour or until dry. Then you can cure as usual. There are videos out there on YouTube if u search.

  19. kp says:

    so can u clean moldy weed?

  20. Joey B says:

    Very informative and well articulated. I was pleased to find this article near the top of the 1st page of my Google search about “weed mold”, particularly because of how much info it contained. Please keep up the great work and keep these all important lines of communication open!

  21. Joey B says:

    I also want to say, in light of reading the “volley” between “Jasom” and “VaporClaus”, that this informative article was made LIGHT YEARS better by the wildly entertaining and humorous back and forth between each of you. I agree with the points, observations, and suggestions made by numerous participants after the article and while I realize that they cant ALL be accurate, (Since they contradict one another) I can easily glean that they are only intending to be helpful. I found Vapor Claus’ idea to be very insightful as well as interesting, and I agree with him and others that Jasom’s comment was uncalled-for, over-the-top, and all sorts of other hyphenated-adjective type of things. I was going to join in the bashing of Jasom for his irreverent posting until I realized that he and vapor claus are ACTUALLY THE SAME PERSON!!! So beware everyone, the “Mastermind” behind the 2 personae is very cunning in their use of the socratic method of dialogued argument in order to prove two contradictory assertions. There is only 1 incredibly insidious reason that someone would go through all that effort JUST to bamboozle the entire lot of anonymous Google searchers who stumbled upon just such a quip-a-cation: CUZ THEY GOT HIGH!!!!!!

  22. hella heated moldy bud says:

    ok soo lets say hypathetically of course i opend up my bag to sum weed that looks like old man winter came and took a big frosty shit on and im sartin to get the kinda mad where (u wanna knuckel punch a baby n the throat)…. ok soo bakeing is out cuz that ddnt sound right to me ne how the dry ice remidy sounds as if it would kill the mold and freeze the moisture keeing the weed nice … as for the air duster as much as i want to say its a wack concept i read the edvidence and seem to think it makes sence… soo on too the peroxide and water will that work on a cuple partialy broke up zips????…. witch method shuld i use???? what about dry ice and air duster in combination? any sugestions r appreciated sorry for my horrible spelling

  23. calmer says:

    To VaporClause – How rude you are to Bob! This blog is intended as a discussion, not an attack. You say the his use of a common curse is Vulger? Well, it’s a adjective that fits, whereas your grandpappa’s saying, “like a tits hog” offensive, vulgar, and unnecessary to the mold discussion. Talk about misinformed? Don’t cut the mold off!!!!, as clause suggests – the spores are also contracted this way, it’s airborne – (insert swear word, please. I would but want to make sure this is posted and not removed for inappropriate words, but I would otherwise make use of each one, in any language to convey what a *^%$% clause’s seems to be ). Clause, You cite research from wikipedia? Another example of your lack of finding solid information. I’m battling cancer and doctors have not only encouraged me to smoke, but explained how to handle the mold. Yes, bake it, but absolutely do not cut it!!!! Cutting the mold releases the spores!!! Dont let it go into the air – you can infect anyone this way with a compromise immune system – even from just the flu. And to insult anyone’s question regarding F and C temperature conversions not only makes you sound like a know it all, but no sense shows that it’s common for people to not know this off hand. His question was asked, showing he felt like this is a forum to feel comfortable asking. You certainly wiped out that opportunity for many of us. So, I am the going down to your level by saying, “you are a (swear word) to attack a another for their research”, right or wrong it may be. Your’s is wrong, AND MAYBE MINE IS TOO, but your an (swear) of the grandest sense for your response.Likely I spelled words wrong in my message, go for it. Or was it grammatical errors you would like to use to insult my intelligence? Bet I’d beat you at chess, any mathematics, and the number of friends I have! I have taught high school math, and statistics in college, yet my exact conversion numbers often escape me. Oh, did I mention I went to Harvard? But I consider emotional inteligence the greatest predictor of one’s ability to contribute to the world. You are not as smart as you believe, otherwise YOU would present with better social skills – same goes for you Jason. The two of you can go “shove it”. Least I know I am not using my best social skills here either, but clearly you need work on yours, as well as your limited control of your anger. An To all others, continue your research and make your own final decisions on how to manage the mold. Clause, my grandpappa also had an expression. He said, “if you can’t say something nice, figure out a way to do so!” rather than “don’t say anything at all”. I am not talking that advice, I guess, because I have no inclination to convert my words towards you. And fair is fair – Go ahead and attack me as well, if you please. Your credibility is lost anyway. Bob, I wish you well and let’s all ignore Clause’s disrespectful response disguised a help. Clause, your a ……, and should change your ways, or keep out of a discussion. I will honor my own advice and not post more negativity. But again, I ask people to research what I have learned about cutting the mold and it’s potential health risks. It may be inaccurate, but I suggest we all just trying to help keep the search going and the insults gone. I would call you a bully, not because it’s a popular subject, but because you post was aggressive and repeated. Plus I was one – as a child – so takes one to know one. Respectful I thank you all for the chance to air my opinions – Clause I think so little of you, but also believe people can change. I grew up and learned how not to bully others. Get offline, grow up and change!

  24. Tarad says:

    How does mold on marijuana edibles behave in relation to this?

  25. jay says:

    Or get a cheap UV light to kill the mold and spores

  26. Rand Al'thor says:


    Ever heard of Freon? Its a mix of fluorocarbon gases found in refrigerators, the same kind of chemicals found in ‘canned-air’.
    A couple of months ago my freezer exploded and a huge white cloud of freon came from it and dispersed in my tiny apartment.
    I called poison control to be safe and they said that you would need to directly inhale a highly concentrated cloud of freon for it to do any damage. Those gasses when inhaled by the body are completely removed only seconds later. They are virtually harmless unless you’re inhaling the gas straight from the can.

    It seems VaporClaus has found an effective way to ‘clean’ moldy weed

  27. Kemokrypto says:

    I am a licensed professional grower in BC, Canada in the top 20 percentile of my class. I say this so you can take my statements as those of someone who has tried and tested all sorts of situations and parameters when it comes to mold, yeast, bile resistant bacteria like e-Coli etc. etc. tested by a local laboratory. First off… If you can avoid it: DO NOT CONSUME MOLDY ANYTHING!
    However,” in my opinion” if perhaps there were a patient who was growing his/her own medicine legally & this person was trapped between no medication for a debilitating illness and consuming something that was contaminated but treated properly… You could look into these procedures:
    1) take all product and freeze with liquid Co2/No2 using a safe mechanism like a whip cream dispenser; dealing with such a task must be performed with heavy duty rubber gloves, face shield and a metal vessel not sealed like a drink shaker. Many trix homes will fall off but the majority of the product should remain intact…
    2) perform above with dry ice (no sealed containers or it will explode as the ice subliminates
    3) put all material in a large stainless pot with a grill at the bottom to suspend above 60 ml of distilled water. Place container under heat lamp or preferably in grow during light period for 6 hours, product will tarnish on outside (turn orangish brown) but retain color and aroma inside, mold will be steam destroyed granted the infra red energy from the bulbs gets the temperature up to 100 degrees Celsius. 158 degrees is only necessary for gray and or black mold and only needs 15-30 min… It will severely degrade the medicinal components of the medicine only leaving behind mostly THCA which is psychoactive but not very medicinal; I would turn it all into oil (Phoenix Tears) via adding Esther or 99.99 isopropyl to material in a NON SEALED BUT COVERED GLASS CONTAINER for 24 hours – 1 month and then slow cooking away the alcohol outdoors in a slow cooker, rice cooker or other non ignition heating device capable of low heat cooking (Esther and isopropyl are extremely flammable and explosive when heated) the result in some hours is a black thick tar that can be use topically, vaporized or eaten if someone decided it was safe to do so.

    3)compost it and do a better job of curing next time; if your in a hurry but want the best possible cure; Cut off hang able branches 18″ or longer, use a clothes drying rack in your transition room or somewhere that has shared air and temperatures of your grow but NO DIRECT LIGHT to hang your “sticks”, hang them on this rack for three days or until the outside feels dry but the stems still bend.
    Cut off the stems and transfer into glass sealed jars and leave for 24 hours in the dark.
    Open and inspect; if hard but moist your golden and only need to open once in a while
    ; if soft and a lil soggy, take out, place in brown bag rolled closed at the top with a fan
    blowing on it overnight or for 4-9 hours (inspecting during process if during the day)
    Once material is stable, keep in glass out of direct daylight and your good for months!

    Hope this helps somebodies!
    got it growing on!

  28. Robin says:

    I just put my bud in the oven as directed and within 10 minutes my oven was smokin and not in a good way…..The shit burnt…….I used an electric oven preheated to 300. Did I make a mistake by preheating it or did you really make a type O and cost me an ounce and half?

  29. Julia says:

    Great Article! I work in a mold laboratory in Colorado, where, Medical Marijuana is quite prevalent. As new regulations hit the industry, I hope people will pay close attention to this issue. Mold can cause serious health issues when inhaled! Keep up the good work.

  30. YouYou says:

    Just did 10 min, 300 C. I cant see any mold, I’m getting pretty stoned off 3 hits. My stuff’s pretty dry though …figured that would happen… Grateful, thanks for the advise!


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