The Keys to Clean Cannabis

August 21, 2019
Figure 1
Figure 1 (click to enlarge): “Cultivation Classroom” columnist Dr. Roger Kern standing with his hands behind him on the left, with the Pathfinder Rover before its trip to Mars. Cleanliness was paramount for this environment, just as it is in today’s cultivation facilities.
Abstract / Synopsis: 

If you are a grower, you know that your main goal must be maintaining a cultivation facility that is free of plant pathogens. Plant diseases can bring down your grow and leave you with a troublesome mess that must be cleaned out and months of lost profits. Recovery from a major disease outbreak is costly in terms of impact on yield and labor costs, not to mention the potential negative impact on your reputation as a grower. Of course, a small level of disease can be tolerated and treated, but you cannot let it get out of hand! In this month’s “Cultivation Classroom,” we identify the main sources of disease that could impact your grow operations.

Every cultivator has their horror stories about plant pathogens and the havoc they wreak. I am talking about those microbial menaces that you can’t even see until it is pretty much too late to have effective eradication without harm to your profits. Whether admitted or not, every cultivation facility has plant pathogens: outdoor, indoor, and greenhouse. However, my focus in this “Cultivation Classroom” is on greenhouse and warehouse cultivation facilities—the expensive controlled environment agriculture (CEA) facilities—we need to prevent the entrance of these harmful microbial pathogens into these special facilities. Growers raise and invest serious money to build these facilities and often give up significant equity to ensure the highest quality in the finished facilities. That investment needs to be protected.


When creating a clean grow facility, the key is prevention. The key to prevention is to start clean. But where does that level of clean start? My ideal cultivation facility would be a cleanroom, similar to those you find at the National Aeronautics and Space Administration (NASA) to ensure that we don’t contaminate Mars and the other planets in our solar system. It sounds pretty wild, but I started out obsessing about microbial contamination in 1995 while I worked for NASA. I was technical group leader of NASA’s Jet Propulsion Laboratory’s (JPL) Planetary Protection Group. Our job was to build the Pathfinder Lander as free of microbiological contamination as humanly possible. We were able to maintain an environment virtually free of microbes. This was accomplished by designing into our facility a number of barriers to maintain a clean spacecraft assembly environment (see Figure 1).  (See upper right for Figure 1, click to enlarge.) We cannot achieve the same level of cleanliness in a cultivation facility, nor do we want to because the costs are prohibitive, but the same general approach applies.

When we create the optimal growth environment for plants in our high-tech CEA cultivation facilities, we create an excellent growing environment for microbes, both beneficial microbes and harmful pathogenic microbes. We start out with good intentions in preparing the growing environment for plants, but in the process, inadvertently, create a perfect environment to foster the growth of microbes, both good and bad.

As a result, you must start with a clean and disinfected facility. Make sure your cleaning crew and staff members wear appropriate protective clothing to prevent microbes, viruses, dust, pollen, and atmospheric detritus on skin and clothing from contacting plants or other surfaces. Make your motto: “Start clean and stay clean!” Before you introduce any new clones, plants, people, or processes into the facility clean every surface with a state-approved environmentally-friendly disinfectant agent, such as a hydrogen peroxide (H2O2) based solution.  The top three “must have” rules to assist with keeping your facility clean are:

  1. Every employee must change into appropriate clean, protective gear before entering the facility. This includes footwear, protective “bunny suit” coveralls, gloves, and beard and hair coverings at a minimum.
  2. No visitors are allowed into the facility.
  3. No decorative plants are allowed into the facility.
  1. Z.K. Punja and G. Rodriguez, Can. J. Plant Pathol. 40(4), 498–513 (2018).
  2. Z.K. Punja, Can. J. Plant Pathol. 40(4), 514–527 (2018).

About the Interviewee

Dr. Hope Jones is Chief Scientific Officer of Emergent Cannabis Sciences—a research, development and advising company—whose mission is to drive scientific innovation within the cannabis industry. Dr. Jones was formally Chief Scientific Officer for C4 Laboratories, a research, advanced analysis, and characterization of cannabis medicine company. She is a graduate of the University of Arizona’s Controlled Environment Agriculture Center (CEAC) where she worked to propagate endangered native species using tissue culture techniques. She is one of a very select few scientists in this country that have extensive experience in utilizing these techniques with cannabis specifically.

About the Columnist

Dr. Roger Kern is a scientist and technologist who cares deeply about the cultivation and health of plants in the cannabis industry. With his PhD in microbiology from the University of California, Davis, Plant Growth Laboratory, he solves the most challenging problems in hydroponics, from studying the root microbiome to developing nutrients and lighting systems to ensure plant health and a disease-free lifecycle. He spent 22 years at NASA’s Jet Propulsion Laboratory as a scientist, technologist, and research leader before becoming the President of Agate Biosciences, a consulting firm for project management, systems engineering, and science in CEA for the past eight years. He leads developments to optimize sustainability, consistency, quality, and yield without compromising plant health. Direct correspondence to: [email protected]

How to Cite This Article

R. Kern, Cannabis Science and Technology 2(4), 16–29 (2019).