Grow Room Air Flow: The Forgotten Bud Stopper

Botrytis. Also called “bud rot,” this term can sound like a curse word for the cannabis cultivator. Because this moldy disease begins inside the bud, it can be difficult to identify during a routine inspection. But once it’s present, the bud can take on a brown-grey color, and then the mold quickly works its way outward to all other plant parts, and then, devastatingly, through the rest of your crop.  

“There are always going to be spores of different molds and diseases,” says John Pratt of Quest Dehumidifiers. “Even at low humidity levels, if you have no air flow and your grow room is stagnant, bud rot can proliferate fairly easily. To break the cycle of mold growth, you want to break up that environment.”

When it comes to air flow, the motto should be, “more is better,” Pratt says, meaning: provide as much air flow as possible without actually damaging the plant. While too much air movement can cause steam breakage, leaf tearing and growth in different directions, Quest’s recommendation is you should always have a steady air flow in your grow up to that threshold.

Quest Dehumidifiers can be placed in both indoor and greenhouse grows to prevent stagnant air. But Pratt says there are a few dehumidification-regulating tips you’ll want to follow:

1. If you have end-to-end ventilation, you don’t want to place your dehumidification near a ventilation duct where it can suck out all the dry air, Pratt says. You’ll want to place it either on the other end, or in the middle. “The last thing you would want is to blow cold, dry air into a dehumidifier, limiting its capabilities. … That’s a big one most people don’t realize.”

    

2. If you’re in an indoor grow, try to centrally locate your dehumidifier, and if possible, place it up high. “It seems counterintuitive, but humidity does rise,” Pratt says. “That said, you can put a dehumidifier anywhere in the space as long you avoid the AC duct and it’s not pouring directly onto a plant. It can perform very well on the ground. We do hear, however, that they perform just slightly better at the top of a room.”

    

3. Understand the relationship between your AC and dehumidifying products. “While the AC units do pull moisture (dehumidify while they’re running), they also have powerful fans,” Pratt says. “Cultivators may think, ‘If I just have my fan running all the time on my AC, that’s just more air flow, which is good, right?’” Not exactly. “Because what can happen is that while the AC is running and condensing, it’s pulling moisture onto its coils,” he adds. “But when the AC doesn’t need to cool anymore, it shuts down its compressor, condenser and evaporator, and the fan will be going over the coils. That means all the moisture it just pulled out of the room is getting pushed right back in. So you’ll see jumps in humidity. … The same thing happened with our dehumidifiers. We used to have the ability to run fan-only, but we took that off because of that exact issue.”

    

4. Utilize an air scrubber to help clean the environment. The air is already filled with tens of thousands of spores, many of which have the capability to contaminate your grow. But an air-scrubbing product with a dehumidifier, such as Quest’s H5 Air Scrubber, can remove some of the fungal spores that can possibly contaminate your grow while you’re pushing air from one end of the room to the other. “It’s got a HEPA filter to clean the air as you’re moving it. You’re not going to get all of the spores, but you will get a lot. HEPA filtration is as high as it gets,” Pratt says, adding that one air scrubber can cover 7,500 cubic feet in a grow facility.

For more information on Quest Dehumidifiers' air mover products, please follow this link.

^{Photo at top: A Quest dehumidifier mounted near the ceiling at a Rhode Island cultivation center.}