Master Grower Tips for Cannabis Growth

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Sherry Ellen Slitts
Sherry has been active in the biotechnology industry since 2010. She is experienced in developing quality management systems and documentation for regulatory compliance under GMP guidelines. Her background in microbiology, cell biology, and aseptic processing provide a scientific context for cannabis production methods. Sherry has a passion for plant science, especially in the areas of tissue culture and bioactive compound extraction.

What cultivation tips does international Master Grower Shlomo Booklin have for you?

Growing marijuana can be overwhelming with so many options for indoor strain choice (we wrote a piece to help you with this: What is the Highest Yielding Indoor Strain for Cannabis?), cannabis technology, types of cannabis, and greenhouse management systems. If you are a licensed producer or master grower, you may be wondering what tips the broader cannabis industry is following and how others are finding success in their cannabis growth.

Whether you are just starting to write your cannabis business plan, or have an established commercial cannabis grow, here are Master Grower tips from renowned cultivation expert Shlomo Booklin that you won’t get from regular cannabis consultants or in cannabis SOPs (Part 1, Part 2).

Carbon Dioxide Enrichment: When and How Much to Use?

GrowerIQ (GIQ): When (or in what type of grow) is it a good idea to utilize carbon dioxide enrichment for boosting cannabis growth?

Shlomo Booklin (SB): Let me start with some background about the cannabis plant. In nature, the seeds are germinated in March/April (Spring), then they grow throughout the summer. Cannabis is a short-day plant, so when days get shorter at the end of summer (August), they bloom, making seeds at the end of Autumn, and then die, keeping seeds in the ground for next year. 

Carbon (C) is one of the universe’s building blocks. Carbon is available to the plants mostly in the form of gas (CO2). In the process of photosynthesis, the plant takes the carbon dioxide (CO2) from the air, combines it with other minerals, and builds more cells (O2 is released back into the air).

In nature, the CO2 level is about 450 -500 ppm (part per million). However, in a greenhouse setting, as the plants use the carbon and release the oxygen (O2), the concentration of the CO2 goes down. Furthermore, in the greenhouse setting, we force the weed plants to grow faster than in nature. The life cycle of cannabis plants will take about 7 months in nature, but we “squeeze” it into 10 weeks. So the plants grow much faster and the concentration of CO2 of the greenhouse air is getting lower, thus, they will need more carbon.  

We normally try to keep about 1200-1500 ppm of CO2 in the greenhouse. A good grower will know that in the first 2-3 weeks of the lifecycle of the plants, they are very small and can not use all 1200 ppm. Therefore, there is no need to pump that much into the greenhouse during this stage. Furthermore, as one can understand, as plants are not active during the dark hours (with respect to photosynthesis), there is no need to provide CO2 at night. 

Towards the end of the lifecycle, or about 3 weeks before harvest, plants are also not growing any further. Therefore the concentration of the CO2 can gradually be reduced. CO2 is relatively expensive, a good grower who knows the facts can reduce the cost of the CO2 by being more efficient and will use the CO2 at the right time and the right dosage.

Commercial Hydroponic Cannabis Cultivation

GIQ: Can hydroponic cannabis cultivation be as cost-efficient as soil?

SB: Yes, especially in places like Ontario, Canada where we are sitting on the biggest reservoir of fresh water on earth. However, what are the risks?

GIQ: Personal preference aside, are there any advantages or disadvantages to hydroponic cultivation for cannabis growth?

SB: Hydroponic cultivation can be very good, however, there are many risks involved. Roots are sensitive to pH. Lots of nutrition elements are not available to the root if the pH is not balanced around 5.8 to 6.2. If one is sure that he can master the water to be “perfect” all the time, then yes!

 However, we are all humans and mistakes can be our “second nature.” Soil is more forgiving, and as a grower you have more buffer for mistakes in your nutrient or fertilizer uptake.

As we know, warm water loses the ability to carry oxygen which is vital for the roots. [Hydroponic weed] pumps that run constantly, warm up the water as well.

Soil, as said, is more forgiving. If you give too much nutrition you can flush the out, if you don’t give enough you might have a buffer from the soil. If you forget to give water, same thing, the soil can last a day or do without water.

As I worked for the past 35 years in so many facilities I know that most mistakes are human error and soil in this respect is more forgiving… especially if so much money is on the line. No one can be 24/7 on the facility and naturally, at times the grower must delegate some of the activity to another person. That other person can be less perfect and small mistakes can be detrimental.    

 I visited an amazing facility a few months ago. About a 15 million dollar investment, everything is nice, really amazing. Everything is of course automatic, from light to irrigation. After 3-4 months into production, all the mother plants started to bloom… Someone forgot to change the light switch from “manual” to “automatic” and the light stayed on the manual setting of 12 hours light, 12 hours dark [which induces flowering]. That company now lost 6-7 months of production, they need to start new mother plants, again for simple human error in botany.

It’s not related to irrigation or hydroponic, however, it shows how devastating simple mistakes can be and when it comes to growing media. Soil or soilless soil (peat, coco fibre, and similar) are much more forgiving. Over the 35 years of my professional career, I have witnessed some really dumb and stupid mistakes that one could write a comedy about! Thankfully companies now have extensive resources to avoid those mistakes, like seed-to-sale software and cannabis consulting.

Cannabis Growth: Preventing Plant Hermaphroditism

GIQ: What are the causes of hermaphroditism in cannabis growth, and how can you prevent that from happening?

SB: Stress, mostly. Though at times stress for the plants is good for the outcome (high THC).  On the plant level, it is still stress. As one knows, we keep hundreds, or thousands of plants, all female, in one area. They are all “sexually frustrated” as they are naturally looking eagerly for pollen and to produce seed. The plants “feel” that they are towards the end of the lifecycle, and soon they will die [and seek to reproduce]. So together with the stress of temperature, water, fertilizer (or lack of it with whoever does the “flushing”). The “cheese” varieties are notorious for hermaphroditism.

Managing Cannabis Pests with IPM

GIQ: Every cultivator should have a pest management plan that will vary based on whether they are growing outside, in a greenhouse, or indoors. Do you have any tips or tricks for preventing and controlling pests and pathogens?

SB: Same as many of the other points, as a medicinal product, there are many restrictions and regulations that determine which pesticide or fungicide one can use on the crop. IPM is not only the right thing to do, but most of the time it’s also cheaper, and safer for the end-user, the patient! 

Some people also using the old trick of having host plants. Lots of the pests go to cannabis plants only since it’s the only plant around. If there are other plants, the pest will “prefer” the other plants. For example kidney beans, both aphids and spider mites love kidney beans over cannabis.  Having few of these plants in and around the facility will attract the aphids to go to the beans and not to the cannabis.

Recommendations for Irrigation Methods

GIQ: When do you recommend hand watering versus using an irrigation system (overhead or drip) for cannabis growth?

SB: One has to remember that many pathogens and plant diseases are waterborne, so one must make sure that all pipes are sanitized periodically. Overall I do prefer drip line irrigation where one can control the amount of water and or nutrition the individual plant will get. Overhead watering will increase the humidity in the canopy and thus more fungus and disease. Lots of growers also recirculate the water after use, and though I truly support recycling, one must make sure that the water is treated.

Cannabis Growth: Nutrients and Soil Selection

GIQ: I know that you have so much experience with all of the different cultivation methods and equipment out there. Likewise, I know that there is a lot of personal preference that comes into play with cultivation methods. Could you tell us some of your favorites for nutrients?

SB: Fertilizers that have been in use for the past 50-60 years in modern agriculture have established themselves as proven and effective. If it’s good for tomatoes and strawberries, it’s most probably good for any other commercial agriculture.

I have come across some “special” fertilizers for cannabis, and lab results have shown that it’s made from “human feces” and had some bad bacteria in it. I do not forget that we are dealing with medicinal plants! I hope all growers that use those “special fertilizers” will send samples to the lab, and make sure they don’t use “shit” (for lack of a better word) as a fertilizer for the medicinal plants.

I am sorry to use that language here, but its frustrating to read and hear about really dumb methods that people are using in growing “medicinal plants.”

Commercial Cannabis Strain Selection

GIQ: What are your favorite cannabis varieties for commercial cannabis growth?

SB: I am not a user of cannabis, so I don’t really know what is considered classic. As said before, I do believe in proper science, clinical trials, and as we all know, a variety that might be helpful to me will have an opposite effect on you. It is so individual. Like many other pharmaceutical products, I believe that trails and research will help us know more. I do like White Widow and Sour Diesel.

Final Thoughts on Cannabis Growth

Each grower and cannabis cultivation facility will have its own methods and preferences, but master grower tips are worth some consideration and may call your attention to some ideas that may not have previously been considered. Cannabis has many unique features but, ultimately, it is still just an agricultural commodity. There is much to gain from insights from established cultivators. When it comes down to it, it is important to pay attention to the basics and have a strong understanding of botany and agriculture.

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