Bud Rot/Mould
4 min

How To Spot And Prevent Bud Rot When Growing Cannabis

4 min
Growing Seedshop

No one wants to have to deal with bud rot, but knowing the signs, and how to handle it can help save the vast majority of a plant.

Bud rot is one of many obstacles that threaten a cannabis grower's crop. Bud rot is particularly devastating because it targets the very reason for the grow in the first place: the sweet and resinous psychoactive flowers. Bud rot is particularly harsh when it strikes in the end portion of the flowering phase, sabotaging months of hard work and dedication. Bud rot prevention is a powerful tool within the toolkit of all growers. In this article, we will cover how to detect and prevent this plight from happening.



Basically, bud rot is a toxic fungal infection that kills or taints the flowers of your cannabis plants. Once germinated, it is highly contagious, quickly moving from bud site to bud site. Fortunately, bud rot can only set in if the conditions are just right, so it can be quite easy to prevent.

Bud rot tends to affect large and densely packed buds, but can be seen across even the loosest of bud sites, especially when growing conditions are wet. You will notice that everything at the bud site, including pistils, sugar leaves, and calyxes, start becoming dark and discoloured. They will also start drying up and shrivelling—even though the rest of the plant remains intact.

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If caught early enough, you may notice white fluff on the surface of the bud site. This is the early stage of mould that will eventually develop into full-blown bud rot. It is the first stage of the infection, meaning there is still a chance to intervene, rescue some of the plant, and take action to prevent others from being infected. This can be very hard to catch though as the fluffy mould doesn’t hang about for long. More than likely, you will see random spots of bud begin to dry out and discolour.

In an advanced stage of bud rot, you may see little black specks on the bud. This is the fungus reproducing. The specks are new spores that are ready to be carried on the breeze to new cannabis plants. Do not breathe it in or allow it anywhere near other plants. When dealing with bud rot, it’s best to wear a filtration mask that can deal with microbial spores. If you spot these signs on indoor plants, it's best to isolate the specific specimen during the rescue process. If you spot it on one or two outdoor plants whilst others remain free of it, it's best to immediately quarantine and/or destroy the infected ones.

One way to get up close and personal with bud rot in the super early stages is to invest in a pocket microscope. These handy devices can be used to zoom in on individual bud sites and regularly inspect them for the early signs of bud rot. This allows growers to take action much sooner, greatly reducing the damage done. Not only are pocket microscopes great for prevention purposes, but they allow growers to really get to know the fine details of plant anatomy.



If bud rot has taken hold, then the best, and really only, thing you can do is cut away all signs of infection as well as anatomical structures proximal to the infected region. Throw this away and ensure it can never come into contact with any other plant. You then need to move your cannabis to a warm, dry place with a slight breeze. From here, you can either harvest your plant as it stands or take a gamble and allow it to ripen.

As tempting as it might be to remove the mould from your buds and dry them for smoking, this is a really bad idea. It's best to take the loss and learn from the mistake. By smoking bud with mould on it, you are essentially inviting spores into your lungs—something that you want to avoid at all costs. Chances are, some of your crop will be free from the disease, so enjoy what you have left when it comes to harvest time and focus on optimal anti-mould environmental conditions in future grows.

Some cannabis growers believe that water curing can save mouldy weed. With this method, buds are placed in a jar with water, allowing unwanted residual substances to fall away, while preserving potency and flavour. Although the success stories of treating mouldy buds with water curing are anecdotal, it may be worth a try! Click the link underneath to find out how it works.

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As mentioned, bud rot is very easy to prevent in healthy cannabis plants as it needs a certain set of conditions to germinate and thrive. It doesn’t matter how many spores your plants come into contact with if the conditions are not right for it to grow and attack. The conditions for germination are as you may expect from a mould. There needs to be:

  • Wet/humid conditions (so watch out after a lot of rain when growing outdoors)
  • Stagnant air/no breeze

  • A cool temperature (anything below 20°C)

So, the best way to prevent bud rot is to make sure these conditions never persist for long, and certainly never at the same time.

When growing outdoors, it can be hard to control such conditions, and the best thing to do is make sure your growing site has a decent breeze and stays warm before you ever put seed to soil. Some outdoor growers will also shake their cannabis plants after the rain to eliminate any excess water droplets. Another option is to construct a tarp over outdoor plants to have more control over the amount of water they receive, keeping them out of the reach of rain. If you decide to do this, make sure that the tarp is supported in the middle. This will allow water to run off the side instead of pooling and potentially collapsing.

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Indoors, bud rot should be very easy to prevent as all of these conditions are easier to control. Just make sure temperatures never drop below 20°C and that you have good ventilation to prevent air stagnation and overly humid conditions.

As a closing note, never use fungicides, neem oil, or other additives to try and fix rotting bud. These are not effective against bud rot and will make the bud you can save taste funny. Some growers try to take preventative measures with specific antifungal sprays during vegetative growth, but this can only go so far. The best prevention is controlling the environment to ensure the above criteria never take hold. Never spray bud with anything!

If your rot has become so bad that there is no hope, cut your losses and destroy the plant. It is better to get rid of it and minimise the risk of spreading it elsewhere.


Written by: Zamnesia
Zamnesia has spent years honing its products, ranges, and knowledge of all things psychedelic. Driven by the spirit of Zammi, Zamnesia strives to bring you accurate, factual, and informative content.

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