drying cannabis in a box

How to Avoid Mouldy Weed During Drying and Curing

Ahhh, harvest time! It’s easily the most exciting time on your calendar. Unfortunately, a tiny little mould spore can ruin all your hard work if you’re not careful. In this article, we’ll show you how to avoid mould while drying, curing and storing your weed, so you can enjoy your buds safely.

Don’t let your guard down after harvest—learn how to protect your buds from mould during the final stages of the growing process.


What Makes Cannabis Buds Mouldy?

The mould that can develop on cannabis flowers, colloquially called “bud rot” by growers, is caused by Botrytis cinerea, a necrotrophic fungus that also grows on grapes, strawberries, tomatoes, and other fruits and vegetables.

Botrytis thrives in warm, humid climates and attacks the living cells of plants or fruit, while feeding on the dead matter. It develops on the stems of live cannabis plants or harvested flowers and slowly grows outwards, which makes it particularly hard to spot. Usually, by the time you spot botrytis on the surface of a bud, it will have almost completely destroyed its insides, leaving it wet, slimy, and smelly.

How to Prevent Mould after Harvest

In the grow room, the principles of preventing mould are maintaining optimal temperature and relative humidity, as well as proper air circulation. Post-harvest, you’ll want to follow the exact same principles to avoid losing your hard-earned buds to mould.


Cannabis flowers have a high water content when they are harvested. Therefore, before you light up your buds, you need to be patient and let them dry till they contain only about 10–15% of water.

Drying your buds is as simple as hanging them upside down from a piece of string or clothesline. Where you hang them is completely up to you, just make sure they are in a dry, dark place where the air circulates freely. Growers typically dry their buds in a designated room or a cupboard/closet. If you’re short on space, you can even hang your buds inside a cardboard box; just make sure to poke some holes in the box for the air to circulate.

Creating the Perfect Drying Environment

Ideally, you’ll want to dry your buds at 18–20°C and 50–60% relative humidity. Some growers like to keep the temperature at the higher end of the spectrum during the first 3 days to dry their buds a little faster, before drawing the temperature back down to slow the process. You’ll know your buds are ready to be cured once their stems snap easily. This can take up to 2 weeks, but it will vary depending on the temperatures and humidity levels you’re drying your flowers at.

If it’s hot, we recommend drying your buds in a lightly air-conditioned room. You can also use air-conditioning to drive down the humidity if you live in a particularly humid area. Finally, remember to use fans to circulate the air around your buds to dry them evenly and further prevent mould from forming.


Once your buds are nice and dry, you’ll want to cure them in airtight jars for at least 2–3 weeks (or more, if you have the patience).

As buds cure, they continue to lose moisture, but at a much slower rate. This slow release of moisture helps bring out the aromas and flavours in your flowers and also purges any impurities. Unfortunately, the build-up of moisture inside your curing jars can also create the perfect conditions for botrytis spores to grow.

Trim Like a Pro and Keep Things Clean

Before you cure your buds, you must ensure they’ve been trimmed to perfection. Old foliage like leaves and stems can trap humidity and create the ideal environment for mould. Whether you prefer trimming wet or dry, make sure your harvested flowers are free of unnecessary plant matter before you pack them into your curing jars.

Another key step to preventing mould when curing weed is cleanliness. Make sure your jars are sterile and dry before you start filling them with flowers. Also, only fill your jars to 3/4 of their capacity. Keep your jars in a cool, dry, and dark place (light degrades THC and can drive down the potency of your buds).

The Art of Burping

To further prevent mould when curing weed, we recommend you open (or “burp”) your jars 2–4 times a day to remove and replace the old, humid air. After about 1 week, you can start burping your jars less frequently (1–2 times per day), as the flowers will be dryer and release less moisture.

If you’re worried you’ll forget to burp your jars (or you’re lucky enough to have a huge harvest on your hands), you can use humidity packs to control moisture levels inside your jars. For curing cannabis, we recommend using packs that help maintain 62% humidity.

Keep a Watchful Eye

Finally, the best protection against mould is a keen eye. Make sure to regularly inspect your buds during the curing process. If you suspect some of your buds to be developing mould, separate them from the rest as quickly as possible to avoid the fungus spreading even further.


Once you’ve cured your weed for at least 2–3 weeks, it’s officially ready to be smoked. You can continue storing your flowers in your curing jars, using humidity packs to avoid them drying out too much over time and to maintain humidity inside the jars at optimal level. Remember that your buds will continue curing and their flavours should intensify as they mature, so don’t smoke your way through the stash too quickly!

Keeping Mould at Bay—Bottom Line

It’s vital that you don’t rush your way through the final stages of the growing process. While we know you’ll be anxious to sample your home-grown buds, taking the time to properly trim, dry, and cure your flowers will take them to the next level in terms of flavour, aroma, and potency, all the while keeping them safe from mould.

And if you do find buds that are affected by the dreaded fungus, make sure you remove them and closely inspect the rest, as smoking mouldy weed is dangerous for your body!

Humidity Packs Protect Against Mould

Humidity packs are small and simple tools that pull in moisture from the surrounding environment. When the moisture level starts to climb, they’ll absorb water particles that would otherwise serve as a breeding ground for mould.

Moisture Fighters Offer Two-Way Control

At Royal Queen Seeds, we engineered our own humidity packs specifically for curing cannabis buds. Our Moisture Fighters possess a two-way control mechanism that allows them to both trap and release moisture. This enables them to take in excess moisture while also preventing your flowers from becoming too dry and losing their flavour.

Humidity Control Pack

A Plant-Based Product With No Preservatives

Our Moisture Fighters are crafted with the health of the environment and your buds in mind. Each packet derives entirely from plant-based materials and contains absolutely zero preservatives. You don’t have to worry about any unwanted chemicals leaching out and contaminating your pristine organic flowers.

Humidity Indicators Keep You Informed

Moisture Fighters remove any guesswork from the curing process. Each pack features a card that houses a humidity indicator. This reusable piece of kit will let you know when you need to swap out your Moisture Fighters. Knowing exactly when to do this means you’ll keep the curing environment perfect during the entire process.

How to Use Moisture Fighters

Moisture Fighters are extremely easy to use. Keep your flowers juicy and terpene-rich using the steps below.

  1. Remove Moisture Fighters from their packaging, making sure not to open the Fighter itself.
  2. Place a Moisture Fighter and the humidity indicator alongside your buds in their curing jar.
  3. Let the Fighter do its thing. When the dot on the humidity card turns from pink to blue, swap out the Humidity Fighter for a fresh one.
  4. Reset the reusable indicator back to the pink setting to keep track of the new Fighter.

Afraid of losing your precious buds to mould? Click and read everything you need to know on preventing mould when drying and curing cannabis flowers.

How to dry and cure cannabis?

Understanding how to dry and cure cannabis is of vital importance to all growers of marijuana. Drying weed properly is essential for high-quality and enjoyable marijuana. This article will explain all you need to know about the subject of marijuana drying or curing, a topic which is often rather neglected by beginners.

Why does cannabis need to be dried?

Once the cannabis buds have been successfully harvested, there is still plenty of residual moisture and chlorophyll in the flowers. Immediately after harvest, 75% of the flower mass is nothing but water. If you were to smoke the buds right away, it would really scratch your throat and be almost inedible.

The goal in drying is to reduce the water content of the buds to drop to less than 20%. The optimal amount of water content is about 10 -15%. In order to reach this state, you need to allow about one to two weeks drying time.

Water loss reduces the total mass of the buds so you expect a lot of shrinkage. However, the amount of THC remains the same, leaving more THC on less mass so the buds are much more potent. You need to consume much less cannabis to achieve the same effect.

If the cannabis buds are not dried at all or if they are not dried for an adequate length of time, there is an acute risk of mould formation during later fermentation or cures. When storing the buds in closed containers, the excess moisture from the buds would quickly escape and become moldy.

Water isn’t the only thing that disappears after the drying process. Chlorophyll – the substance that gives plants their green colour – is also degraded. That’s why the buds in the process quickly lose their green colour. This is a good thing as chlorophyll is rather distracting during consumption and causes the typical scratching and coughing in the throat when smoking.

Moreover, more flavours are “released” in the buds, which would otherwise be masked by moisture and chlorophyll when smoked. Dried weed has interesting and complex flavours.

How long to dry cannabis after harvesting?

Drying cannabis will take some time so you have to be patient. It’s recommended to dry your cannabis for about 1-2 weeks. Of course, after all this work, you probably can not wait to finally smoke your specially grown plants. But as a grower, it is essential that you are patient. Your buds will not run away so don’t take the risk of ruining all your hard work!

And all the whole effort is definitely worth it! In addition, successfully drying your own cannabis is an awesome feeling, because you know that you have done something yourself and the anticipation is just indescribably great, so embrace the need to wait!

The best methods for drying cannabis

The most important element of drying is that it happens slowly. Why does it need to be slow? Water takes some time to migrate outward from the core of the flowers and then evaporate. If drying happens too quickly, the buds inside remain completely wet even though they are already totally crumbly outside. At the same time, there is still plenty of chlorophyll in the cells.

Before drying, trim your heads carefully. Cut and eliminate all unnecessary leaves and trim the stems so that each branch is about two centimeters longer than the stem.

The best method is to dry the heads while the buds are still on the branches. The trimmed shoots are hung upside down in a closed and dark and well-ventilated room. When it comes to thinking of places to hang them, you can let your creativity run wild. You can hang them on a thread with clothes pegs or tie a knot with string. You can use racks, clothes hangers or any other homemade construction. You could even use garden canes – the possibilities are endless!

The advantage of drying whole branches is that the thinner branches are a good indicator of the progress of the drying. Once these can no longer bend and instead “crackle”, the buds are sufficiently dried. The risk of mould is also slightly higher, as water deposits can form on the branches. Make sure you have enough space, as the branches should not touch under any circumstances. There should always be enough space between the branches to allow air to circulate – more about this later.

Alternatively, you can separate the buds directly after harvesting and trimming the branches and lay them out on a drying net. The advantage is that you do not need as much space and they are easier to handle. The buds can be laid out on several levels and be surrounded by air. The risk of mould is lower than when drying whole branches. However, there is a possibility that the outside buds may dry a bit too quickly. You should, therefore, downshift the fresh air supply (e.g. via an exhaust fan) as much as possible.

Drying techniques: drying nets and drying ropes

These are the two methods that are highly recommended. The choice of technique depends on the type of crop and the size of the plant.

Drying nets for cannabis

Net drying is preferred for large crops. You could use a square or round net, it doesn’t really matter. Compared to the spreading ropes, these upright cylindrical nets allow significant space savings in the drying room.
These nets have several layers, which allows one to order the heads by size or date of cut. It is also possible to reserve one or two stages for the plant material intended for the extraction of resin, such as leaves or heads that are not very refined. In order to facilitate the drying process, the important thing is to prevent the heads from touching each other.

Drying ropes for cannabis

Drying ropes are most often used for drying outdoor plants, which generally have much larger branches. The disadvantage of this method is that it requires much more space than the drying nets.

This technique involves cutting the branches of the plant one by one, and hanging them upside down, avoiding them touching each other. This is essential because in case of contact, the heads may dry out badly and botrytis type fungi may appear. The contact surface between the head and the air must be optimal, that is why it is useless to suspend the plants before cutting at least the large leaves, which also contain a lot of moisture.

Bad methods for drying

You may have come across tips for drying cannabis on newsprint or paper towels, but this method is extremely susceptible to mould! The contact with the paper does not facilitate the necessary air exchange. The water escapes from the buds and settles where they come into contact with the paper so does not evaporate. This type of environment is the perfect breeding ground for mould!

How to dry cannabis buds fast?

What you should not do is to artificially accelerate drying by placing the buds in a hot environment, such as a microwave, oven or similar. Too high temperatures cause an extremely uneven drying of the buds. They are extremely dry and crumbly on the outside, while they are still completely humid inside. Also, chlorophyll does not get enough time for degradation.

The aroma also suffers from drying under heat. Many terpenes (flavours inside the plant) are sensitive to heat and can be destroyed by slightly high temperatures (as low as 30ºC). Quite simply, the buds lose their taste due to the heat.

The equipment you need to dry weed

In addition to a suitable place, there are a few other pieces of kit that will help you to successfully dry your weed. You should ideally assemble the things before the harvest begins.

Tip: When you dry in the grow box, you should have the items ready to hand.

  • Thermo/hygrometers
  • Cord/clothesline or drying net
  • Circulating air fan
  • Shears

Things to consider

In order to keep an eye on the temperature and (relative) humidity, you should invest in a digital thermo-hygrometer. It should ideally be a model that displays Min/Max values so you can see the extent of the RH fluctuations. If your drying room is very humid, you can still install a dehumidifier with a tank. This should reduce the drying time and the risk of mould.

Air circulation
In order to avoid the formation of moisture pockets, the air in the drying room must be circulated by a small fan. Place it in a corner of the room, orienting it so that it does not blow directly on the heads: the air must be stirred without shaking the plants.

Another fundamental factor is temperature. The aromas and flavours of cannabis are largely due to molecules called terpenes. These compounds are volatile and are lost under the action of heat. For your crop to retain its aroma, never put it to dry more than 25º C.

To see if the air is circulating properly in the drying room, simply check the temperature and relative humidity using an electronic thermo-hygrometer, and adjust the fan and humidifier to adjust at the desired levels.

In addition, your crop must be immersed in the dark to avoid the denaturing of the molecules responsible for the qualities of your grass. In the presence of light, THC degrades into other less psychoactive forms such as CBN in particular. When the final product contains traces of this cannabinoid, it is usually a symptom of poor drying/ripening.

If you follow all our drying tips, your cannabis heads should be ready for ripening in 1-2 weeks (normally when the plant stems begin to crack when you bend them).

Curing cannabis in glass jars

For curing, we recommend storing the heads in glass jars or tight-vac containers. Their hermetic sealing system prevents any air exchange with the outside. This helps to homogenize the moisture level of the plant material and promotes a gradual transformation of cannabinoids.

When placed in jars, the grass should be protected from sudden changes in temperature and direct sunlight. The product will gain in quality over weeks and months until reaching its maximum quality level around one year of ripening.

Where should cannabis be dried?

To properly dry cannabis flowers, you need a suitable room with the right temperature and relative humidity (RH). The room should be rather cool and relatively dry.

Temperature and RH are two opponents. When the temperature rises, the humidity decreases. And vice versa. The more the temperature fluctuates, the more the humidity will fluctuate. If the RH exceeds 70%, there is a very high risk of mould!

The room should not be too big, we recommend an area of less than 5 m². The smaller space or the box, the easier it is to keep temperature and humidity at the appropriate level.

Optimally, the room should be sealed so that no smells can escape to the outside.

Optimal conditions:

  • A space as small as possible (less than 5 m²)
  • 15°C – 20°C temperature (and as few fluctuations as possible!)
  • 30-50% humidity
  • Absolute darkness
  • Possible air exchange

A grow box fulfills all these conditions, the fresh air can be regulated with the exhaust fan with timer. Grow boxes made of wood or chipboard are more suitable than grow tents made of fabric, as they isolate the temperature more effectively.

Drying weed in a cardboard box

As long as you only dry a small amount or aren’t worried about the smell, a cardboard box is quite suitable for drying. The biggest problem with the carton is the smell. Depending on how much you are drying, the buds will quickly spread a penetrating marijuana smell throughout the room. An ozonizer helps against the smell. This can neutralize the cannabis stink in the room, but then only up to a certain amount.

After a week or two, your weed should be perfectly cured or refined and ready to smoke. You can determine when it is ready by taking a head and bending the rod in the center with your fingers. If it breaks easily, then it is completely dry.


Make sure you store your cannabis in an opaque and airtight container. Well-stocked and stocked heads of a variety of quality, like our Big Amnesia autoflowering, can retain their power and flavour for years to come.

There you go! We hope that you will love the results and we wish you the best for your future crops.

Drying weed is utmost important for the quality of your weed! Wondering how to dry weed and how to cure it? Check it out! ]]>