A Beginners Guide To Mold

The Vault Cannabis Seed Store

Mould can be a death sentence for a crop, it spreads fast and can be tricky to spot. Once it’s spotted we need to know how to treat it. Different types of mould need to be treated differently. There are also a lot of steps that growers can take to stop mould from forming in the first place. Mould is unpredictable, fast and can happen at any time. We must equip ourselves with as much knowledge as possible so that we don’t lose any of our precious buds.

Spotting Mould

Being able to notice mould as quickly as possible is essential if we want to save our babies. There are a few different types of mould that show in different ways so keeping a close eye on the leaves and buds is essential.


This particular mould is usually known as bud rot and is quite common and is not unique to cannabis plants. It can be hard to spot early on because it starts life in the centre of the bud and moves its way out. If we notice that the leaves are dry or that the buds don’t appear to be growing this can be a sign of botrytis. Take a peek inside the bud and if any spots are grey or brown a fungus has likely started growing. This mould can also form during the drying and curing stages if there is excess moisture hanging around.

Root Rot

This mould is very similar to bud rot but affects the roots. This sort of thing is most common in hydroponic growing if the roots are drowned but can also happen if pests get into the growing soil. Again it can be tricky to spot, especially in soil growing, because it is first noticeable in the roots. If the roots become mushy and start to turn brown it is likely they are rotting. Check the roots if the plant shows signs of pretty much anything else. It can pretend to be overwatering, a nutrient deficiency, the leaves may dry out and curl or wilt. Essentially if the plant shows these signs and doesn’t react to treatment it is important to have a look at the roots.

Powdery Mildew

This mould is likely the easiest to spot as it forms on the leaves first. Though it is technically in plain sight it can be extremely difficult to tell it apart from the trichomes forming on the leaves. Unfortunately, this sneaky mould can be deadly as it stops the plant from being able to photosynthesise. Just as it sounds this mould looks like a white powder that slowly spreads all over the plant. If the mould succeeds in spreading the leaves will start to die, then it should be pretty clear that there is a mildew issue. This mould is fast-acting and spreads like wildfire so it is one to look out for.



Unfortunately, the usual best way to deal with this kind of infection is to throw out the infected buds to stop the infection spreading to other plants. If we want to try and save the buds we need to reduce the humidity and try to slow the spread of the mould. If the mould grows more slowly we can spray it with a mould spray. This is not guaranteed to work and if the buds get too far on and start to deteriorate they will need to be removed or they can put the other buds in danger.

Root Rot

In most cases, it is almost impossible to successfully treat root rot. The plant will likely die or be severely stunted so in most cases it’s best to just get rid of the plant. However, if a grower was desperate to treat the plant they could submerge the roots in a mix of bleach or baking soda in water. A small amount of either of these substances could help to clean the roots and kill off an infection.

Powdery Mildew

This is one of the mould types that can be treated successfully, as long as we spot it nice and early. Remove the affected plants from the growing space to ensure they don’t infect their sisters. Remove the leaves that appear to have been infected and then spray the rest of the plant with a fungicide. This will hopefully kill off the mildew, though it will alter the taste of the buds which isn’t ideal. Always check the other plants for signs of infection and try to reduce the humidity in the grow space.

Avoiding Mould

There are some steps we can take to try and ensure that our plants are safe from mould altogether. The best way to treat mould is usually to stop it from forming. Mould loves humidity and excess moisture as well as cramped plants and heat. There are a few things that we should keep an eye on to keep our growing space safe.

  • Monitor the humidity and temperature. Humidity should never get above 60% and the temperature should stay at around 20 – 25 degrees celsius.
  • Ensure there is plenty of airflows, especially in a greenhouse. Greenhouses and indoor growing spaces can create stagnant ambient moisture that is perfect for mould. By inserting fans and ventilation we can keep the air moving and stop mould from setting in.
  • Prune the plants to make sure the plants have plenty of space between branches. Not only will this allow the air to flow through the plants but if there is a hint of mould it will stop it spreading as quickly to the rest of the plant. Dense bud structures will trap moisture and allow mould to breed.
  • When growing outdoors make sure not to outwater the plants. Too much water will attract pests and bugs which will often in turn cause mould.

Mould is a nightmare for growers, but if we are careful we can stop it before it has a chance to start.

Remember: It is illegal to germinate cannabis seeds in many countries including the UK. It is our duty to inform you of this fact and to urge you to obey all of your local laws to the letter. The Vault only ever sells or sends out seeds for souvenir, collection or novelty purposes.

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*Photo from Unsplash

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