How to Prevent Cannabis Fungi

Cannabis Fungi: If you have grown your own cannabis in the past or are currently growing. You will be well aware of the hard work and precious time that is necessary to be successful.

Many environmental factors are required for germination, the vegetative stage and during flowering. There will be many potential problems you will face. As a cannabis grower, fungal rot can be one of the worst. The reason fungal rot is extremely important to try to prevent is that it has the potential to wipe out entire crops. It’s important to be able to identify this problem early and know how to stop the fungal rot as quickly as possible.

Fungal Rot

It’s a terrible thing, to realize a few days before harvest time that something is wrong with your crop. Months and months of hard work can all go to waste if you find yourself facing a fungi problem. Aspects such as humidity and temperature are important variables to consider. However, other factors such as cleaning your grow space and pruning are top priorities too.

Unfortunately, fungi aren’t limited to just the flowering stage. It can present itself during the early stages and can also be a problem during the drying process. One thing is certain, if you want to prevent fungi you must always be vigilant during your grow.

Fungal rot generally attacks the buds but can affect the roots, stems and leaves too. The buds will develop a sort of greyish/white dust. Infested leaves will dry out while stems become brownish, more fragile and ulcerated. The buds will also become paler and when touched they will feel loose and will eventually be covered with a cotton-like growth.

How to Prevent Cannabis FungiMost Common Fungus

The main factors that will influence fungi growth are temperature and humidity. The higher these two are, the higher the risk of developing fungi growth. In order to prevent your plants from falling prey to a fungus such as botrytis, monitor these factors closely. Many preventative measures need to be put into place from the get-go. If this is done correctly, it will help your grow be much less stressful. You will have the peace of mind that fungus rot won’t sneak up on you.

Cannabis plants grown in wet environments are just as at risk of getting fungal rot as those are high and humid temperatures. Even when you have completely eliminated the botrytis colony from your grow, the spores can remain on the plant for years. Then if conditions favor the fungus, it will start growing once again.

Making sure your growing space is completely sterile and clean is also a very important factor to prevent fungus. If you want your plants to remain healthy through the entire grow you must make sure that the area is always spotless. Make sure you sterilize all the grow equipment and tools and remove any decomposing plant matter. A fungus can spread on your hands so avoid touching the plants or buds.


As our cannabis plants begin to flower, they will slowly mature and get large dense buds. During the later stages of flowering, the buds will be more at risk of developing fungal rot. This is because the buds are unable to ventilate as well as before and this lack of fresh air can cause fungus. If this happens you will either be forced to cut before the flowers are fully developed or harvest later and have bud full of fungus.

Ok, we know that very bushy plants with large colas are appealing to the eye but these are also more at risk of developing mold and botrytis. Growers are advised to top their plants and introduce LST (low-stress training). By topping the plant you will get a reduction in flower size.

By doing this, you will get buds that are smaller in size but there will be more of them and they will be healthy. This is a better option over larger buds with high humidity content and so are more prone to mold and fungi.  Low-stress training (LST) is a good growing technique to use to train the plant to grow in a chosen shape. This will help you avoid bushy plant structures that are more susceptible to botrytis.


Both indoor and outdoor growing you will take the same precautions regarding water during the flowering stage. Temperature and humidity must not be forgotten but during the last phase of flowering, you must pay close attention to the amount of water you give your plants. This is a key aspect to focus on in order to avoid bud rot. Wait until the ground is completely dry outdoors before watering or the pot is lightweight enough indoors. This is to make sure you don’t overwater your plants during this last stage.

It’s important to take all the precautions to avoid fungus as early in the growth as possible. Although there are many methods you can use to fight fungal infections, you will be in trouble in the run-up to harvest. This is because you won’t be able to use any chemical product to kill the fungi. These products have a very small safety margin and can damage your health if they are used close to harvest time.

Drying Phase…

Don’t underestimate the importance of the drying process because you managed to get this far without developing mold or fungi. You need to be aware that fungi can attack even during this last stage of growing. You must be extremely careful at all times for possible fungi developing.

We know that a sterile environment, water, temperature, and humidity are key factors that influence mold and fungi growth. But mold and fungi can also develop during drying. You can just imagine how heartbreaking it will be to go through all the hard work of growing only to find mold covering your bud.

The reason we dry our bud is to remove the majority of the remaining humidity and moisture inside the flowers. The most common method grower’s use today is to hang your cut cannabis trees upside down from a washing line. Make sure to leave enough space between each tree so they don’t touch each other.

It’s important to accurately control the temperature and humidity levels in your garden. The ideal range will be the temperature set to 20 degrees C and the humidity level on 50% where possible. Keeping your plants as close to these will ensure t you hat botrytis never have a chance at destroying your crop.

…Is Important

If you have deep pockets then we suggest investing in humidity control equipment. This is a must-have in every grow room. A humidifier and dehumidifier is a great option and which one will depend on the climate conditions of the drying room. Your dry room must always be a dark space. This is because light breaks down THC so a dark room will help preserve quality.

If you are able to keep all the environmental factors and variables within the required range, you will be more successful at keeping mold away. The temperature and humidity are the most important to monitor but water must also be watched closely during the final stages. Remember to take all the necessary precautions early on in the grow to be as successful as possible. Your plants will definitely reward you for your effort by producing the best possible bud.


~ Seedly Team


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