How to Clean Your Grow Room After Powdery Mildew

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That thing that is sticking on your plant, as though you sprinkled powdered sugar or flour over it, is a fungal infection called mildew.

It is common in plants, especially in cannabis, cultivated indoors. Growers don’t like to see it on plants because it does more damage than good, and that is why they constantly seek information on how to clean their grow room after mildew infestation.

Powdery Mildew in Plants

Powdery mildew is always too visible and ugly for anyone to like. They are dangerous fungus infections that compete with your plants for photosynthesis.

And because your plants aren’t getting the needed exposure to useful light, for optimal photosynthesis, they become weak and unhealthy. No farmer wants to invest so much on cultivation just to have unhealthy and weak plants.

Advanced mildew will cause discoloration in the pigmentation of your plant. Hence, a once healthy green plant may become yellow.

Although mildew cannot kill your plants, it can make them very unhealthy and weak. Conversely, products made from unhealthy plants may lead to serious health issues for humans when consumed.

Hence, mildew is directly harmful to plants as well as humans who rely on them for consumption.

How to Prevent Powdery Mildew?

The environment is one of the key hosts of powdery mildew. This is because fungus thrives well in a very humid space.

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Hence, as a grower, you need to ensure the consistency of the temperature and humidity in your grow room. Under-ventilated and damp areas are breeding spaces for mildew, so it is important to keep the humidity in your grow room between 45% to 55% during the blooming growth stage and between 20% to 40% during the flowering stage.

If your grow room is nonetheless humid, then getting a dehumidifier to help reduce the percentage of humidity in the air is an effective alternative.

As a grower seeking to eliminate mildew, it is important to understand that mildew is similar to bud rot and other plant damaging diseases. Hence, they spread by spores which can be carried by air, water, human visitors, and even pets.

Since they rely on ventilation, one spore could wreak gruesome havoc. It then becomes important to have human visitors wear protective suits and sanitize their hands before coming close to your plants, especially if you are growing a commercial quantity. Avoid having pets in your grow room too.

Also, always leave enough space between your plants. You don’t have to gather so many plants than a grow room can obviously contain.

The disadvantage here is that a fungus infection, such as mildew, would easily infect all the plants. Leaving space between your crops will help you notice an affected plant just right in time before a wild spread.

Quarantine infected plants as soon as noticed. Also, switching off equipment such as fan or ventilator systems will help reduce circulating the mildew spores in other plants.

Removing Mildew While You Still Can

While the most preventive measure is to get your clones from the right sources and never let pets and or unprotected persons, who are potential spore carriers, into your grow room, you can still salvage the situation in case of an eventual mildew infestation.

Although farmers try to avoid spraying their plants, it may be imperative to use a tropical or organic treatment such as neem oil, apple cider vinegar or sodium bicarbonate, when you notice early mildew stage on plants.

If only one of your plants is affected, the best option is to quarantine or get rid of it if you may.

Sulfur burners are other desired alternatives to pesticides. They are pH eliminators and they lower the pH level of the surfaces upon which mildew can grow

Ozone generators are another alternative to removing mildew. Ozone is a great sterilizer and would help to sterilize all surfaces that may support spores and aid mildew infestation.

However, if the mildew has gone far in affecting your crops, be open to harvesting what you can and starting with a clean fresh slate.

Starting afresh, after a powdery mildew disaster, will require an effective cleaning of your grow room.

How to Clean Your Grow Room After Powdery Mildew?

Cleaning your grow room after powdery mildew is very important. This will help you put an end to mildew issues by removing all hidden spores ahead of your next planting exercise.

Farmers can take any or all of the following steps when trying to clean their grow rooms.

1. Wash your grow room with bleach and water or hydrogen peroxide

This is perhaps the commonest method. All you have to do is measure out adequate water and bleach, depending on the surface area, using three ratios of water to one ratio of bleach.

You may use a pressure washer if you have one but if you don’t, simply wipe all surfaces in your grow room with this bleach solution.

If you have a natural soil flooring in your grow room, make sure to cover the soil with a carpet or weed barrier fabric. Vacuum surfaces when applicable.

Instead of bleach and water solution, you may use hydrogen peroxide but never mix bleach with hydrogen peroxide. It has to be either of the two.

2. Pay attention to the Intake Filters and vents

If your grow room has vents, there is a very high possibility that it has hidden spores. Don’t neglect them when disinfecting your grow room. Clean thoroughly.

Also, if your ventilating system has intake filters, remember to take the filters out to wash and to disinfect.

3. Never use pesticide or washing agent directly on your soil

This is the entire reason why you cover your soil with a non-permeable weed barrier before you wash your grow room.

Since spores may find their way to the soil, you may disinfect the surface of your soil by spraying organic anti-fungal products or vinegar into the soil.

However, if you can, it is more effective to get rid of the soil and bring in new unexposed soil into the grow room, especially if the mildew impact is really much.

4. Ventilate after wash and keep humidity under the watch

Remember the reason you are dealing with mildew in the first place is as a result of high humidity. Hence, after disinfecting your grow room, try to ventilate the area for at least seventy-two hours before bringing new plants in.

Depending on your preferred ventilator system, a six-inch oscillating fan or more, as your grow room may require, will be a great ventilating device.

Humidity after disinfecting your grow room should be below 30% for the next seventy-two hours before bringing in new soil or a new plant, and then adjusting the humidity level as the growth stage may require.


Mildews are the enemies of quality harvest. They make a grow room a fertile ground for breeding, and their sole aim is to rob your plants from all necessary benefits they need to stay strong and healthy.

The good news is that getting rid of them isn’t so difficult. Following our simplified approach, on how to clean your grow room after powdery mildew, will help you overcome another terrifying mildew attack, and set your plants on the right path to staying healthy and strong.

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