Special Report - State of the Growing Environment

March 6, 2020

Climate Control Among Top Cultivation Challenges

Cultivating cannabis requires a delicate balance of several factors—among the most significant of which are climate control, plant nutrition, lighting and genetics, not to mention the business/financial components. Research participants in the 2020 “State of the Growing Environment Report” indicated their greatest cultivation challenges include “cost” (42%), “pest and disease management” (37%), “humidity control” (28%), and “temperature control” and “watering/irrigation” (both 20%).

All of these factors tie into the cultivation environment, from the cost investment in the facility, equipment and oftentimes labor required for a controlled climate and healthy crop to the humidity and temperature controls required to prevent pests and diseases.

And while “pest and disease management” was ranked by just slightly more than a third of study participants as one of their greatest cultivation challenges, 71% of participants indicated they have had pest and disease issues in their growing operations during the past year, including the top culprit, powdery mildew (42%). Of those who indicated they have grappled with pests and disease, the largest number (44%) cited “external contamination” as the cause of those struggles. Many believe poor climate control was at play, as 36% attributed outbreaks to “unbalanced humidity,” 26% indicated a “lack of airflow” as the cause, and 16% reported “uncontrolled temperature” was an issue.

Cultivator Climate Preferences

Ideal temperature and humidity can vary greatly depending on the geographic location of a grow, facility type, time of day and the plant growth stage, to name a few factors. Achieving appropriate temperature and humidity levels is crucial to proper plant growth. As Mark June-Wells, Ph.D., principal of Sativum Consulting Group, wrote in a previous issue of Cannabis Business Times, “With very low humidity, the plant is drawing water from the soil at a very high rate, and if the humidity is too low, the plant is unable to draw water at a rate equal to the loss through the stomatal openings … which slows the photosynthetic process (due to carbon limitations) and leads to stress, slow growth and compromised yield.” Conversely, diseases thrive in humidity levels that are too high. This importance was illustrated in this year’s study, as 95% of participants indicated they control humidity within their growing spaces and use multiple methods to do so. The majority (55%) use “ventilation,” while another 51% use “air conditioning,” and 49% use “stand-alone dehumidification.”


A majority of participants (66%) keep daytime temperatures between 70 and 79 degrees Fahrenheit during the vegetative stage. However, nearly a fifth of participants (19%) said they prefer higher temperatures when plants are in veg, dialing up to 80 to 84 degrees. There was less of a consensus for preferred humidity levels in this stage among participants, however. A plurality of participants (33%) reported a preference for humidity of 50% to 59%. Twenty-two percent preferred a range of 60% to 69%, while 17% desired levels of 40% to 49%. A fair number (13%) reported that they keep humidity at 70% to 79% during this stage.


Most participants (73%) again reported that they stay within that 9-degree temperature range (70 to 79 degrees Fahrenheit) in the flowering stage, although 12% indicated they maintained their rooms at temps between 80 and 84 degrees. As with the vegetative stage, participants’ ideal humidity levels varied greatly when examining study results in the flowering stage. The plurality (34%) reported keeping humidity levels in their flowering rooms between 50% and 59%, but close behind are those who keep levels between 40% and 49% (31%). Nearly a fifth of participants (18%) set the dials to less than 40% humidity at this growth stage.


The Importance of Airflow

While temperature and humidity are often the focus, proper airflow is just as important to maintaining a healthy grow, as David Bonvillain, owner and principal of Elite Cannabis Enterprises/Elite Botanicals, noted in a previous issue of Cannabis Business Times. Cannabis requires a much heavier airflow than traditional horticulture crops, he noted. “I need circulating airflow through the entire environment at a pretty good clip,” Bonvillain said. “I need channels of air on a low zone so I’m moving air around the lower canopy. If you don’t, you increase your chances of mold and mildew and pests significantly.”

Despite its importance, many cultivators (37%) say they rely on “anecdotal expertise” as their primary layout strategy. Another 29% sought advice from an “engineer/contractor,” while 16% took the “manufacturer’s recommendations.” Fourteen percent reported that they have no airflow layout.

Those participants who map airflow in their facilities (86%) said that the three most important factors when laying out airflow in flowering rooms were “balancing temperature and humidity in room” (70%), “size of room” (54%) and “number of plants” (47%).

There was not a strong consensus among participants regarding enriching with CO2, although the majority (55%) reported using CO2; 42% said they do not.

Svitlana | Adobe Stock

HVAC Priorities

Results from the 2020 “State of the Growing Environment” study revealed participants consider many factors when planning to purchase HVAC systems, chief among them “size of facility” (73%). Other important aspects they examine include “target growing temperature” (67%), “number of lights” (53%) and “target growing humidity” (51%). When deciding which HVAC system to buy, those who were directly involved in purchasing once again noted several priorities that were important. The top 3 include “performance/efficiency, lead time” (78%), “price” (69%) and “customer support” (56%).

About the Research and Participants

Third-party researcher Readex Research conducted the study and compiled the data for the 2020 “State of the Growing Environment Report.” Cannabis Business Times sent the study questionnaire to subscribers with known email addresses and/or e-newsletter subscribers located in the U.S., Canada or other (unknown) North American locations in January 2020.

Results are based on 108 participants who indicated they own or work for a licensed operation that cultivates cannabis for sale in the U.S. or Canada in an indoor or greenhouse growing environment. The margin of error for percentages based on the 108 participants who indicated they work for a cultivation operation that cultivates cannabis for sale in an indoor or greenhouse growing environment is approximately ±9.3 percentage points at the 95% confidence level.