Every marijuana grower needs at least one reliable dehumidifier for their grow room. Here’s why…

Fighting Gray Mold

Gray mold fungus ( known scientifically as Botrytis cinerea and also called bud rot or bud mold) is everywhere. It attacks hundreds of plant species including fruits, vegetables, ornamentals, and cannabis. B. cinerea is only one of at least 20 different species in the genus Botrytis, but it’s the most pervasive and pernicious one, and has wreaked havoc on indoor and outdoor cannabis plants for decades.

Growers try many methods for defeating gray mold. These include:

  • Attempting to block gray mold spores from getting into grow rooms and onto plants.
  • Using fungicides as foliar sprays and as systemic feed materials.
  • Attempting to find cannabis strains naturally resistant to bud rot.
  • Using ultraviolet light to kill gray mold or at least control its growth so an infestation is less disastrous.
  • Using less nitrogen and watering less frequently.
  • Altering garden environment by lowering humidity to below 50%. Gray mold hates it when grow op humidity is below 50%

Unfortunately for growing marijuana, gray mold is a very resilient and clever fungi. In industrial agriculture, growers notice that expensive, complex fungicides that used to kill gray mold no longer work. That’s because gray mold benefits from rapid reproductive turnover leading to genetic adaptability. Scientists have even seen the fungi implement genetic adaptations in real time during crop cycles–the mold evolves immediately so it can reduce or totally resist the effects of the fungicide!

Gray mold’s tenacity and destructiveness are primary reasons you must have a dehumidifier when you’re growing cannabis indoors because only by lowering grow room humidity to between 42-49% can you effectively block a Botrytis cinerea attack or reduce its harmfulness once an attack has started. The other methods mentioned previously are mostly ineffective.

Bottom line: if you’re growing big fat buds and your grow room humidity is above 50% and temperatures are in the average range for indoor grow ops (73-84°F), you better have a dehumidifier, or you may see gray mold destroy your buds.

Drying & Curing Cannabis Requires Humidity Control

Drying and curing marijuana properly is an art and a science. Many cannabis growers do everything right all the way through harvest, only to dry and cure their buds so badly that the buds’ value is diminished or even erased.

Marijuana buds need several days of mild temperatures (72-77°F) and humidity in the 47-56% range to dry at maximum efficiency for preservation of cannabinoids and terpenoids. The most serious growers have a dedicated drying tent or drying room with filtered, pristine air, no direct light, a dehumidifier, and climate control.

And guess what…big fat juicy buds that are at risk for gray mold while still on the plant are still at risk while drying and curing. And gray mold isn’t the only airborne pathogen that can infest drying and curing buds. Aspergillus fumigatus is one of several so-called storage molds or fungi that can infest buds after harvest. These pathogens and gray mold can survive by going dormant in a freezer, and then roar back to wreck the buds when the buds are thawed.

Worse yet, Aspergillus and other storage pathogens can infect your respiratory system– there’s at least one verified case of a marijuana consumer contracting a lung disease from tainted bud and dying.

Most of us have no way to control humidity in a drying room or chamber other than with a dehumidifier. That’s why a quality dehumidifier is an essential piece of gear for growing marijuana.

Vapor Pressure Deficit & Transpiration Management

Vapor pressure deficit involves the interactive relationship between grow room temperature, relative humidity, and your plants’ ability to breathe (known as transpiration).

Your plants intake water and carbon dioxide and they off-gas oxygen and water vapor. In fact, much of the water you give your plants through their roots ends up as transpired water vapor, creating a humid microclimate in the grow room. High humidity combined with the wrong temperature range can create problems with vapor pressure deficit. These  problems block marijuana leaves from easily taking in and sending out gases. This slows photosynthesis, overall metabolic vigor, and nutrients intake and internal transfer, leading to slower-growing plants, longer, costlier seasons, and lower yields and potency.

The good news is you can use a dehumidifier to alter vapor pressure deficit and induce plants to speed up or slow down their transpiration and metabolism. For just one example of how this is an important strategy you want to have handy, consider plants with nutrients problems that require a root zone flush. Problem is, flushing oversaturates the root zone, creating hazards for roots that negatively impact plant metabolism and growth. By adjusting vapor pressure deficit (using your dehumidifier to alter grow room humidity) you encourage your plants to suck excess moisture up out of their soggy root zones and send it out as vapor through their leaves until the root zone is at the right level of moistness.

Again, the bottom line is: every serious cannabis grower should have a dehumidifier.

Finding a Great Dehumidifier

Most of us growers have relied on dehumidifiers you buy at Lowe’s, Home Depot, Amazon, or hydroponics stores. These dehumidifiers are usually in the $200-400 price range.  What most of us aren’t aware of is that most of these generic dehumidifiers are inefficient, ineffective, noisy, messy and in some cases, unsafe.

Witness the fact that one of the world’s largest dehumidifier makers (Gree), responsible for a variety of dehumidifier brands, issued a massive dehumidifier recall after their units were said to have caused nearly 500 fires and at least $20 million in property damage. Millions of units from well-known dehumidifier brands have been subject to manufacturer recalls from the U.S. Consumer Product Safety Commission, beginning in 2002. These include such big names as Danby, DeLonghi, Honeywell, Kenmore, Keystone, Perfect Home, Professional Series, Frigidaire, GE, Danby, ComfortAire, Sunbeam and Sylvania.

I know growers who had fires caused by dehumidifiers that were properly installed and used. In one case, the fire not only led to the loss of the entire grow op, but also to the fire department notifying the police, and the grower being arrested!

Even when low-priced dehumidifiers aren’t  burning your grow op down, they’re wasting energy, generating excess heat, and not pulling enough water out of your grow op air. In fact, I’ve experienced or witnessed the following all-too-common with el cheapo dehumidifiers:

  • Poor drainage via leaky hose attachments.
  • Poor logistics and other defects for on-board bucket storage of water.
  • Unreliable shut-off that allows bucket storage overflow.
  • Inferior hardware, casing, materials.
  • Unreliable controls for setting and maintaining target humidity.
  • The unit is just too damn noisy.
  • Generates too much heat.
  • Doesn’t remove enough pints of water daily from the air.
  • Inefficient compressors and other components, creating excess electricity usage.
  • Inaccurate, misleading specs that exaggerate the unit’s water-removing capacity.
  • Weak warranties and inept or nonexistent warranty service.
  • Frequent breakdowns.
  • Risk of unit catching fire, causing electrical shorts, or causing electrocution.
  • Defective wheels, and/or unit is very heavy, so it’s hard to move around.

Fortunately, I don’t have to deal with those problems because I found an innovative, reliable, American dehumidifier manufacturer. I discovered them by noticing that whenever I visited professional home grow ops and impressive commercial grow ops I only saw one dehumidifier brand: Quest.

I asked growers and facilities managers about Quest and they all said Quest units are the grow op standard because they’re durable and reliable, suck more water out of the air faster using 50% less electricity than cheaper units, have a safer electrical amp draw and peak use spike, are American-made, and come with a five-year warranty and exceptionally grower-centered technical and warranty support.

Quest is a subsidiary of Wisconsin-based Therma-Stor LLC, which was created in 1977. Initially, Therma-Stor made a proprietary line of heat recovery water heaters. Now, Therma-Stor manufactures Santa Fe brand portable home dehumidifiers, Ultra-Aire whole house ventilating dehumidifiers, Phoenix air scrubbing, water extraction and dehumidification units, and Quest high-efficiency commercial dehumidifiers.

The Quest units are so powerful and fun to use compared to generic dehumidifiers we’re used to. They’re meant to be elevated so they can use gravity and/or a condensate pump to send condensate water to drainage or to be used as nutrients water. Elevating the units also means they don’t take floor space from plants.

These are the rock-solid industrial-strength dehumidifiers you see in grow ops that have hundreds of lights and thousands of plants. Licensed, commercial growers who have hundreds of thousands of dollars riding on each season count on Quest to keep humidity in range so their crops are safe from molds and other problems.

You might have read what I just wrote about using dehumidifier water in gardening and said to yourself, “Hey, wait a minute, I heard that distillate water from air conditioners and dehumidifiers contains contaminants that harm plants.” I asked Quest about this, and they said that inferior dehumidifiers can deposit harmful amounts of elements such as zinc, copper and aluminum into condensate water. But Quest uses the highest quality materials, manufacturing protocols, and engineering, and it hired third-party labs to do a series of tests using different Quest units–tests that found that condensate water from Quest units was so pure that it met or exceeded drinking water purity standards, and is safe to use for hydroponics watering.

Another thing I like is that Quest is part of a larger climate control consortium, so it can offer you more solutions than other companies can. Every grow op has different climate control challenges, and I’m happy to report that the people at Quest and their allied companies are very creative and effective when it comes to finding you the humidity control options that work best for you. For example, they’ve solved some grower’s problems by having them use Ultra-Aire whole house dehumidifiers rather than using a unit inside the grow room.

Quest and Ultra-Aire units cost more than Home Depot-style generic dehumidifiers but for this very crucial piece of growing marijuana equipment you definitely get what you pay for. Growers who’ve done the math will tell you Quest units pay for themselves after a few seasons because they use much less electricity than cheaper dehumidifiers and remove more water from the air per hour.

I like the industrial-level air filtration, safety features, quiet operation, reduced heat output, capacity, precise humidistats and easy set-up and operation of Quest and Ultra-Aire units. Another reassuring fact is that when I’ve contacted Quest for technical support, you can easily see they’re dedicated to grower satisfaction, and are technical experts when it comes to using their products in every kind of growing situation.

And of course, it’s worth a lot to know your dehumidifier is American-made and won’t burn your house down, and that Quest units are known to run like a champ, providing years of flawless service that gives growers great peace of mind.

The main thing to remember is every serious cannabis grower needs a reliable, energy-efficient dehumidifier, and the most popular, effective and reliable ones I’ve seen in the growing marijuana industry are made by Quest.