Updated on December 18, 2017.
Medical content reviewed by Dr. Joseph Rosado, MD, M.B.A, Chief Medical Officer
If you’ve ever inhaled marijuana smoke, the odds are pretty good that you’ve also inhaled a few mold spores. While we encounter these spores in many of our surroundings, they’re usually not that dangerous for people who have healthy immune systems.
However, if your weed has a great deal of mold, or if you’re a medical marijuana user, you might be more susceptible to a wide range of health issues such as coughing, flu-like symptoms, breathing problems and more. Moldy weed could be extremely dangerous if your immune system has been compromised.
Here’s some information on how to avoid mold-infested weed and how to prevent mold from affecting your plants.
What Causes Moldy Weed?
The predominant cause of moldy weed is moisture. Many people make the mistake of packaging their plant in containers without first making sure there’s no moisture in the buds. This is a recipe for mold, because it thrives in a moist environment. The vast majority of growers who supply dispensaries are honest and will take whatever precautions are necessary to reduce the chances of mold. However, there are a few unscrupulous ones out there who will actually add a bit of moisture to their buds in order to increase their weight so they can make more money.
If you cultivate your own plants, you may have read that burying your buds in the backyard in order to promote the growth of a particular type of mold will make them more potent. This is a bad idea for several reasons, the most important being it would be almost impossible to ensure that exact type of mold would grow on the plant.
In addition, burying marijuana buds will just about ensure that the THC (the psychoactive ingredient in cannabis) in the plant will be destroyed.
How to Spot Mold on Marijuana
Marijuana plants come in a variety of colors, so it would be very easy for the untrained eye not to be able to tell the difference between normal buds and those that have become infested with mold. In fact, trichomes can sometimes look like mold.
The best way to spot mold is to put the plant under a black light. If there are spores present, they will emit a distinctive green color. But you can also tell mold is present if you see any unusual dark green or black spots, or you notice white- or gray-colored strings coming off the plant. Mold spores will also affect the smell of the plant and create a musty odor.
There are a few types of mold that will typically affect weed. Here’s some brief information on each:
Aspergillus — This is one of the most common types of mold spores, and one you will encounter in just about any type of environment. The aspergillus strain is blamed for a wide range of problems, such as causing lung disease in both animals and humans and causing food to spoil. It’s even to blame for foul-smelling shoes.
Botrytis — The Botrytis strain also goes by the name of “bud rot.” While it’s more likely to contaminate grapes, it can do a number on a cannabis plant as well. In some extreme cases, it can kill an entire cannabis plant.
Penicillium — There are actually versions of this strain that are quite beneficial. They are used to make cheese as well as the powerful — and often life-saving — antibiotic Penicillin. Other strains, however, are extremely destructive. Not only can they ruin plants, but they can also cause a great deal of harm to humans as well as animals.
Preventing Moldy Weed
In order to survive on a marijuana plant or in just about any other environment, mold needs a humidity level of no less than 15 percent. So, if you’re storing your weed, make sure it’s completely dry before securing it and make sure you do so in a dry place. If you’re growing weed, put your buds in a dark area with plenty of ventilation once you harvest them.
Some people like to keep their pot in jars so it stays as fresh as possible. If you’re one of them, make sure you open those jars at least once a day to get a good amount of fresh air. Should you encounter buds that have become too dried out and you want to try and rehydrate them, you’ll need to be careful. The two most common methods are water and orange peels, but both present a risk for mold accumulation. Water obviously increases moisture, while orange peels are extremely fertile breeding environments for mold.
You should always try to avoid smoking weed that has become infested with mold, of course. But there are certain times where your cannabis may have a slight amount of mold and you might feel you have no choice.
If you’re running low and that’s all you have — and it has only been slightly contaminated — there’s a precaution you can take to stay as safe as possible. Put the weed on a cookie sheet and bake it at 300° F for about 15 minutes, which will kill some of the more common strains of mold.
It’s extremely important to note that if you suffer from any sort of respiratory issue, or if you have a compromised immune system, the risk of smoking moldy weed is simply too great. You cannot take the risk, because it could result in a major health issue. Some people might tell you that if you use a bong or water pipe you’ll be filtering out the mold, but that’s not the case. This approach would filter out maybe 15 percent of spores at best.
You also shouldn’t use any edible product containing moldy weed, because that could be even more dangerous.
While you don’t have to live in fear of moldy weed, you should have a healthy respect for it. This is especially the case if you’re a medical marijuana user. Don’t be paranoid, but do be careful and stay away from any cannabis you don’t trust.