Part 3 of Dr. Robb's Cultivation Blog Series: Flower Power, AKA Breaking Bud


Bud. Nug. Cola. Popcorn. Bangers. Trees. Broccoli. Sinsemilla. Buddha.

These nicknames all reference the most important part of the cannabis plant: the flower. Granted, the cannabis plant has many useful parts (most obvious that comes to mind for most people is the hemp fiber); but in this particular discussion, I want to give a couple hints and tricks that is focused on the production of flowers, also known as the flowering cycle. It is important to note that cannabis is a dioecious plant. All this means is that there are separate male and female flowers on completely separate plants. If you’re growing cannabis to smoke the flower, you are primarily interested in the female flowers.




If you read last month’s blog, you will remember that we can keep most cannabis plants in a vegetative state by giving the plants short night times or by interrupting the night with a brief period of light. (There are some cultivars of cannabis that go into flower without the long night stimulus. These varieties are typically bred from a low cannabinoid species of Cannabis called C. ruderalis. They are also called “auto-flowering” plants.)

Triggering the flowering cycle in cannabis requires the opposite: long, uninterrupted periods of dark. Typically, indoor and greenhouse growers provide their crops with 12 hours of dark per 24-hour period to trigger flowering. The flowering period can last anywhere from 55-70+ days to fully mature (next month we’ll talk about the harvest, but this month’s blog will focus on what to do before then). During this roughly 2-month period of time, it is the cultivator’s focus to provide a great environment to promote flower and ultimately cannabinoid/terpene production.



I come across a lot of growers who treat their crops like they are their children, but I’m here to say that it’s ok to give your plants a little tough love to promote some better growth. (For the record, I do not think there’s anything wrong with this. In fact, I typically take the stance that there are several ways to successfully grow any type of plant. If it works for you, and you cultivated a plant that you appreciate, then you successfully grew your plant.) If you think about cannabis horticulture, you are growing high-quality flowers. Flower production is the first step angiosperms or flowering plants, take in an investment in the next generation. Many plants will invest more into the next generation if an exogenous stimulus threatens their survival. Not that plants can think, but if they could, they would probably be thinking something along the lines of:


“Oh crap. I may not make it much longer. I better do everything I can to provide for my kids so that they have a better chance than me.”

Or something like that. There is practical evidence of this working outside of cannabis as well. Date Palms are also dioecious plants, and one of the problems that date growers can face is if the male and female plants don’t flower at the same time. Date farmers can induce uniform flowering across their orchards by physically whipping the trunks of their trees. The physical stimulus does slightly damage the trunks, but it promotes the trees to flower all at once and with more voracity. Now, I’m not suggesting we cannabis farmers go around whipping our crops (although, I have not designed an experiment to test the null hypothesis that whipping one’s cannabis plants does not have an effect on crop yield and quality as compared with a control group that is not whipped), but there are ways we can give our plants a false stress that promotes more robust flower production.

One such example is introducing chitin as a soil amendment. A few fun facts about chitin: Chitin is second most abundant natural biopolymer in the world. Chitin is the primary component in fungal cell walls and the cell walls of arthropods (insects). We have seen evidence that introducing chitin (or its water-soluble derivative, chitosan) into the root zone will promote increased yield and increased defense against fungal and bacterial attack. The plant can sense the presence of the chitin, which in the plant’s world could mean a fungal attack, and therefore increases production of secondary metabolites used to defend itself and pushes more energy towards the flowers. A little tough love here pushes the plant to be more resilient and yield more. All good things.



Photo by Joy Ridge Farms

Le Chatelier’s principle, or “The Equilibrium Law”, refers to the ability to predict change in a chemical reaction by changing the conditions, one of which could be the concentration of the reactant in the chemical equation. For example, if I increase the reactant in a reaction, I can predict that more product will be produced. With crop production, it is not a straight chemical reaction since we have this biological entity of a cannabis plant, but the basics of the principle are the same. More reactant, more product.

In this case, the product is more flower, more cannabinoids, more terpenes. So, what is the reactant in this little equation? Carbon dioxide. THC is a 21-carbon molecule. It’s expensive for the plant to make, so if you provide more of the raw materials up front, the plant can create more of that desired product. CO2 injection in the ambient environment around your crops will increase yields and produce buds with significantly more terpenes/cannabinoids. Earlier, I mentioned that the 2nd most abundant biopolymer on the planet is chitin. Well, the first most abundant biopolymer on Earth is cellulose, which is the compound that the plant uses to build its cell walls. Guess what cellulose is made of: carbon, hydrogen, & oxygen. That carbon comes from the CO2 it “breathes” in through the leaves.

Blueberry Muffin from Humboldt Seed Company

I will admit that CO2 injection is nothing terribly novel, but if there’s one thing I want to impart you with is that you can get away with growing your cannabis plants in warmer environments if you have higher concentrations of CO2 in the air. The reason why this is because of a pretty significant plant enzyme called ribulose-1,5-bisphosphate carboxylase/oxygenase, AKA RuBisCo.

RuBisCo is the enzyme that takes CO2 out of the air and fixes it in order to make it biologically available (that’s the carboxylase function). Unfortunately for this particular enzyme, there’s also an oxygenase function that creates a waste compound instead of fixing CO2. When RuBisCo oxygenates, it becomes less efficient because it doesn’t fix that CO2, but instead it creates a waste product that the plant now has to get rid of. The oxygenase function of RuBisCo becomes more pronounced as temperatures rise. However, by increasing the concentration of CO2 around the plants, we can manipulate RuBisCo to preferentially carboxylate even in warmer temperatures.



If you’re growing in an indoor facility, this means you can run your rooms warmer during the flowering period, which will end up saving you some money on air conditioning. Additionally, the warmer temperatures mean the plant’s respiration rate will increase, and I can tell you from a significant amount of experience in this particular area that increased respiration results in increased production more often than not.



Now all you outdoor growers are probably thinking right about now, “Well, that’s just fine and dandy, Dr. Robb, but there’s no way I can inject CO2 for my outdoor grown plants.” Au contraire. There is a company called AG Gas that has novel technology that allows for CO2 injection even in outdoor climates. The company ran an experiment with UC Davis and Fresno State on using their technology to inject CO2 in field tomato production. They saw an increase in yield of just under 130% as compared with the control group. I personally saw their similar experiment with cannabis, which resulted in a significant yield increase as well.



There is so, so much more to the flowering process that I could continue to write about; however, I wanted to just give some tidbits and things that I find interesting and hopefully, you find helpful. For example, the next time you’re at trivia night and the question, “What is the 2nd most abundant, naturally occurring biopolymer on the planet?” comes up, you will be able to immediately utter “Chitin!” Or if you’re in a hostage situation, and your captor says, “I will let everyone go if someone here can tell me what the most abundant enzyme on the planet is.” Congratulations, Mr. or Ms. Hero!

You just saved everyone’s lives because you were able to say “RuBisCo” with confidence. More importantly, you now know that you can use CO2 injection to run your rooms a little warmer while not giving up a drop in yield in your flower production.

Before I end this, I would like to blame the relaxed candor of this blog post on sleep deprivation. My wife just recently gave birth to our 2nd child (she’s rocking the motherhood thing by the way), and our sleep has been less than ample. Now if you’ll excuse me, I’m pretty sure there’s a dirty diaper waiting for me to change it.

Keep cultivating!


The Schedule For The 9-Part Series

Part 1 – Introduction: Meet Dr. Robb (June 19)

Part 2 – Cannabis Veg Cycle (July 17)

Part 3 – The Flowering Cycle  (Aug 21)

Part 4 – Harvest (Sep 18)

Part 5 – Dry and Cure (Oct 16)

Part 6 – Trimming (Nov 20)

Part 7 – Assembly Required (Dec 18)

Part 8 – Maintaining Mom’s and Genetics (Jan 15)

Part 9 – Cuttings and Cloning (Feb 19)

Share This