In North America, you don’t have to look far to find a t-shirt or hat embossed with the iconic cannabis leaf. Avid users are quick to show their plant appreciation using this symbol, but in reality, the true magic lies within the cannabis flower. For growers, all stages of cannabis growth and harvest go into cultivating flower, also known as bud.
The chemical basis of the cannabis experience is based on special types of metabolites found in cannabis. These include cannabinoids, flavonoids, and terpenes. On a very simplified level, cannabinoids such as THC and CBD provide psychological and physical effects, flavonoids provide colour, and terpenes contribute to aroma. Different strains of cannabis have unique combinations of these compounds.
In this article, we’ll walk through the major steps of cannabis plant development. We’ll look at how the Big Three macronutrients affect each stage of cannabis growth, and how they contribute to producing metabolites.
Note: The word “bud” in cannabis lingo does not have the same meaning as the word “bud” in plant science. To avoid confusion, they will be referred to as either (cannabis) bud or (plant) bud.
Cannabis has been cultivated for thousands of years. In the past, research has largely revolved around hemp, or varieties of cannabis that contain very low THC content. However, recent studies are improving our understanding of this fascinating plant. We’re seeing how different environmental conditions affect the production of its unique metabolites.
Most growers generalize the cannabis lifecycle into three: stages, seed, vegetative and flowering. This is only a simplified view. Botanists use a standardized BBCH scale to describe stages of plant development. The scale has nine-steps that classify the major developmental stages by the plant’s appearance or phenotype. This can be helpful in assessing the growth process.
Stages of Cannabis Growth
Stage 0: Germination, sprouting, (plant) bud development
In this stage, roots emerge from the seed. The initial stem (the hypocotyl) and the first leaves (cotyledons) form. This stage ends when the cotyledons break through the soil surface.
Stage 1: Leaf Development
The cotyledons unfold and separate. Leaf development begins as the two cotyledons and true leaf pairs emerge, it ends once the first lateral shoot appears. Leaf pairs continue to emerge in stage 2.
Stage 2: Formation of Lateral Shoots
(Plant) buds along the initial stem develop into new lateral shoots or stems. This process is known as tillering. Tillering is highly dependant on soil moisture, with low moisture conditions driving deeper root systems rather than bushier growth from increased lateral shoot formation.
Stage 3: Stem Elongation
During this stage, the cannabis plant grows rapidly up to its final height, forming nodes along the stem. Nodes are the points on the main stem where leaves and branches form. Spacing between nodes varies among cannabis strains. Indica strains have less spacing relative to Sativa and tend to grow denser and shorter.
Step 4: Rooting
This BCCH stage does not exist for cannabis development.
Step 5: Inflorescence emergence
(Cannabis) buds, referring to the complete flower head of cannabis, are scientifically known as inflorescence. Each inflorescence contains the main stem as well as its many branches ending in clusters of flowers. This stage is where the “vegetative” stage ends and the “flowering” stage begins. This stage is also when female cannabis plants can first be differentiated from the unwanted male plants which contain low concentrations of cannabinoids and terpenes.
Step 6: Flowering
The flowers in each inflorescence begin to open. Within each female flower, there is a pistil that contains the ovary and stigma. These collect the pollen that later fertilizes the ovary, forming the cannabis seed. The ovary is protected by structures known as bracts, which are covered in tiny glandular structures known as trichomes.
Trichomes are found all over the cannabis plant, but specialized capitate glandular trichomes are only found on bracts. These are the only trichomes containing cannabinoids and are responsible for the stickiness found in (cannabis) buds. The “natural cell factories” produce large amounts of specialized metabolites, including flavonoids and terpenes.
Metabolites are present at their highest levels in this stage, meaning it is the optimal time to harvest. Without harvest, metabolite levels will begin to drop off. Growers look for a high bract-to-leaf ratio in (cannabis) buds, identified by a higher weight. Denser (cannabis) buds have a higher metabolite content, and are considered most potent.
Step 7-9: Post Harvest
In these steps, new seeds form and mature and the plant reaches the end of its lifespan.
Nutrient Needs Throughout Development
There are three nutrients that play a major role in plant development: nitrogen, phosphorus, and potassium. These nutrients have different roles by stage of cannabis growth, so it’s important to know exactly which steps require high or low amounts.
In all types of cultivation, nitrogen is responsible for lush, green growth. This is due to nitrogen’s major role in photosynthesis, the production of energy from light. The higher the concentration of nitrogen found in leaves, the higher the concentration of chlorophyll (the molecule responsible for plants appearing green). Nitrogen is transported by plants towards the top leaves, allowing for photosynthesis to be more efficient, resulting in more growth. Nitrogen is key for stages 1 through 3, allowing the plant to capture the energy necessary to grow to its full potential.
However, excess nitrogen in later stages means that your plant will continue to promote growth, instead of allowing inflorescences to develop. Excess nitrogen drives further leaf development, which will lead to a lower bract-to-leaf ratio. Nitrogen can also increase the proportion of male to female plants, decreasing the efficiency of your grow.
Lastly, nitrogen plays an important part in seed formation. This means that your cannabis plant may progress through stages 5 and 6 rapidly and move into stage 7, lowering the harvesting window and preventing the formation of dense, potent buds.
Nitrogen is key for optimal early development. For higher yields, it should be reduced in later stages of cannabis growth.
Phosphorus is involved in every growth phase and is vital for maximum crop yield. Phosphorus’s interaction with micronutrients is extensive and phosphorus levels are often targeted by growers as an indirect method of controlling micronutrient availability.
Plants require large amounts of phosphorus. It is part of the energy currency used in cells, adenosine triphosphate (ATP), and is used in nearly all cellular functions. From initial development to flowering, phosphorus is in constant demand. Phosphorus is also directly involved in the formation of cannabinoids. If phosphorus in the soil is consumed and not replenished in the early stages of cannabis plant growth, stage 5 and stage 6 the plant will produce fewer cannabinoids. This will lead to less potent crops.
Phosphorus levels in the soil are positively correlated with THC concentration and THC yield.
Phosphorus is key in all stages. It should be replenished in later stages of cannabis growth for higher yield and potency.
Most known for its regulatory function in pH and water uptake, potassium also activates over 50 plant enzymes. Some of these enzymes trigger plants to move from stage 3 to 5. Supplementing with potassium reduces the time it takes for your crop to reach the flowering stage.
Additionally, higher levels of potassium are correlated with a longer inflorescence period, meaning higher concentrations of cannabinoids, flavonoids, and terpenes. While a direct link has not yet been found, enzymes directly responsible for cannabis metabolite production may also be activated by potassium.
Potassium drives (cannabis) bud formation and leads to a more potent crop.
BlueSky Organics & Flower Two
Whew! We covered a lot of important information in this post. Understanding the stages of cannabis growth is key to troubleshooting issues encountered in growing. It can help you fine-tune your process, leading to your best harvests yet.
As we learned, nutrient needs can shift between stages. Delivering the perfect ratio of nutrients can result in significantly higher yields and quality of (cannabis) buds. Denser, more potent buds can be achieved by applying BlueSky Organic’s Flower Two. Carefully designed for simple application during the flowering stages of growth, Flower Two adds phosphorus and potassium to your soil when it needs them most.
The result? A harvest of potent and flavourful cannabis.
- An H.R. et al. (2012) Flower initiation and development in Cymbidium by night interruption with potassium and nitrogen. Horticulture, Environment, and Biotechnology. Volume 53.
- Coffman, C.B., Gentner, W.A. (1977) Responses of greenhouse-grown Cannabis sativa L. to nitrogen, phosphorus, and potassium. Agronomy Journal. Volume 69.
- Cowett, E.R., Sprague, M.A. (1961) Factors Affecting Tillering in Alfalfa. Agronomy Journal. Volume 54.
- Fageria, N. K. “Potassium” Handbook of Plant Nutrition. 127-158
- Hopkins, B.G. “Phosphorus” Handbook of Plant Nutrition. 66-111
- Livingston, S.J. et al. (2019) Cannabis glandular trichomes alter morphology and metabolite content during flower maturation. The Plant Journal.
- Mishchenko, S. et al. (2017) Phenological growth stages of hemp (Cannabis sativa L.): codification and description according to the BBCH scale. Agricultural Sciences.
- Pilbeam, D.J. “Nitrogen” Handbook of Plant Nutrition. 17-52
- Raman, A. “The Cannabis Plant: Botany, Cultivation, and Processing for Use” Cannabis.
- Raman, A., Joshi, A. “The Chemistry of Cannabis” Cannabis.
- Small, E. (2016) Cannabis: A Complete Guide.
- Spitzer-Rimon, B. et al. (2019) Architecture and Florogenesis in Female Cannabis sativa Plants. Frontiers in Plant Science. Volume 10.