How to Prevent Mold When Curing Cannabis and Hemp

One of the most important things to consider when storing cannabis is how to prevent mold. Mold can occur in any phase of cannabis and hemp cultivation due to how mold reproduces. It sends microscopic spores up into the air in hopes they will find a nice damp place to land and grow.

Since mold spores are airborne, be sure to take special precautions in each step of the growing process. HEPA filters and ventilation for grow rooms or storage locations is recommended to prevent mold. These filters are highly effective, but can be costly in certain applications. Luckily, they aren’t the only line of defense again mold growth in storing cannabis.

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Dry Container

Keeping the storage container clean and dry is key to preventing mold or mildew. The most common storage containers are glass or bpa free plastic.

Lids with rubber seals or air lock features that allow them to remain self contained and air tight. Containers are recommended to be clear/transparent so that the buds can be inspected without having to open the container. This can go a long way in extending the duration of how long they can remain in usable condition.

After a container is empty, it should be cleaned with soap and water. Allow the container to dry completely before using for storage again.

[PRO TIP] Glass is a common choice for storage container because it has less likelihood of scratching. This minimizes the surface area where spores can take hold, which also helps to prevent mold.

Oxygen Absorbers / rH packs

Oxygen absorbers, or rH packs (Relative Humidity Packets), help prolong the life of stored buds.

How Do Oxygen Absorbers Work?

Oxygen abosorbers control the moisture content within the container used for storage. These pack maintain moisture within one percent of the rating on the label. Most commonly 55% or 62% for organic consumable goods.

This allows for optimum storage humidity levels and lowers the likelihood of mold growth especially in humid areas.

[PRO TIP] Some growers prefer to vacuum seal their cured buds. This works for short term storage, but does not allow for proper ventilation. If the amount of moisture within the bud is still too high, mold can occur.


A cool, dry, dark place is ideal for storing cannabis long term. The cool (below 75°F) temperature, absence of moisture, and lack of UV light reduces the likelihood of bacterial or fungal growth to prevent mold.

Given that the buds are organic matter, they can not be stored indefinitely. After 6 months in the best conditions they begin to decompose. So it is recommended that they are used before the 4-6 month mark.

Frequency of Checking

Occasionally, if a foggy film or condensation is noticed within the storage containers they will need to be opened and vented. The more frequently the storage containers are opened the more likely chance mold has to form.
Opening the containers creates a change in pressure and humidity between the open air of the room and the container. Mold spores descend from the open air in the room into the container, landing on the buds, raising the likelihood for mold growth.

This is the primary reason that a clear glass or plastic container is recommended for storage purposes and easy inspection. This will allow you to observe the buds conditions without opening the container.

Warning signs

If you notice any water droplets, fog, or condensation build up on the inside of the storage jar, take immediate action. The container should be opened for proper ventilation. This is the the last chance you will have to save the buds.

Inspect the buds for white powdery mineral deposits, or white/grey web-like fuzzy growth. This is a sign of mold/mildew growth and buds should be disregarded.

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Salvaging Tips (When Possible)

If you notice any of the above warning signs then you have a few option in salvaging the buds before mold sets in.

  1. Quarantine the moist/foggy container
  2. Open container for ventilation
  3. Remove buds, set aside for further drying/clipping
  4. Clean container with soap/water or alcohol
  5. Allow container to dry completely, or use a new dry container
  6. Clip away any viable signs of white mold (if any other color dispose of bud)
  7. Increase airflow on the buds by small fan (preferably near a HEPA filter)
  8. Once the buds are dry to the touch place back in dry clean container
  9. Store in a separate cool dry dark place
  10. Monitor 3-4 times a day to watch for signs of moisture build up
  11. Clean all equipment (sheers, trays, gloves) and dispose of any contaminated material (trash bags, gloves, clippings)

Why Mold Matters

Consuming cannabis with mold can have serious health effects based on the method of consumption.

Smoking moldy buds can dramatically increase the risk of respiratory and circulatory infections, especially in people with compromised immune systems.

How to Prevent Mold When Storing Cannabis or Hemp

How to Spot Mold on Your Harvest

The most common way mold is recognized on cannabis is though hyphae.
Hyphae are long white/gray web looking strands that can appear anywhere on the bud or stem. Once mold spores land they use hyphae to spread a root system for more nutrient/moisture absorption.

Mold spores are present in each part of the grow process. Since cannabis is organic matter, it is impossible to completely insure that it will always be protected from mold or bacteria.

All cannabis will eventually begin to decompose, which is why aged cannabis is often avoided. Decomposition cannot be completely stoped, but you can make buds last longer by controlling humidity. Common methods include dehumidifiers, regulating temperature through ventilation, and keeping light exposure to a minimum.

Can’t I Just Freeze My Cannabis Buds?

Cannabis buds can be frozen for long term storage solution, but this comes with it’s own assortment of problems.

Freezing separates the trichomes from the buds themselves. This drastically lowers the quality of your product. However, Frozen buds are still great for making kief, especially for hash production.

Freezing can also increase the harshness of the taste. Freezer burn can also occur if containers are not sealed 100% securely.

Freezing is possible,but is not a recommended solution due to these factors. A more effective option would be proper crop cycling. Allowing for a constant crop of cannabis in each stage of the growing process. This allows for a consistent stream of production and allows for higher quality control when it comes times for maintaining inventory.

Good Cure = Easier Storage

A major factor in keeping your buds stored successfully is managing the curing process. Curing takes the majority of moisture out of the buds; thus promoting an environment that will keep for a longer, more sustained period of time. And even though mold will eventually occur in all buds, by following these simple steps you can insure the maximum shelf life for your crop.

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