Light

Photons

Provides needed energy and used to produce sugars via photosynthesis 

Measured with photons/light intensity.

Classified by Light spectrum.

Plants use photons as an energy source needed to complete photosynthesis as they carry Energy proportional to their frequency.

Inverse square law states the intensity of light changes inversely to the square of the distance of the source

 I=1/d²

Mathematically, double the distance, energy will be ¼ intensity.

Cannabis light intensity 

Light intensity affects different processes within cannabis and can vary with condition. General growing intensities are as follows.

• Seedlings and clones 200–400μmol/m²/s.
• Vegetative phase 400–600μmol/m²/s, 
• Flowering cannabis 600–1500μmol/m²/s

Light Spectrum

The entire range of electromagnetic radiation consists from various wavelengths which determine the color on the spectrum.

Generally plants use the photosynthetic active range (PAR) of spectrum.

Different chemicals react ideally to different light wavelengths.

• Chlorophyll A (red,violet, blue)
• Chlorophyll B (blue,orange)
• Carotenoids (green,blue) help with eliminating free radical oxygen during photosynthesis to prevent cell degradation
• Phytochrome (red/infrared) Signals plant to sleep or wake up  and causes florogen production. Has two states Pr (orange/yellow) and Pfr (red/infrared). Helps to keep cannabis in a vegitative state or to blossom.

Cannabis wavelength 

Cannabis prefers the following light colors.

400-460nm in vegitative growth

580-700nm in flowering

Photosynthesis

Photosynthetic cycle and the calvin cycle

6CO2 + 6H20 + (energy) → C6H12O6 + 6O2 Carbon dioxide + water + energy

Calvin cycle 

Does not need light only CO2

3 CO₂ + 6 NADPH + 5 H₂O + 9 ATP → glyceraldehyde-3-phosphate (G3P) + 2 H⁺ + 6 NADP⁺ + 9 ADP + 8 inorganic phosphate

Light Schedule

Cannabis requires 18-6 or continuous 24-hour light during vegitative growth period (little to no dark hours).

Cannabis requires a 12-12 light schedule during flowering.

it is important to keep the dark hours light-free.

Air

CO2 Oxygen osmotic potential

Internal pressure regulated by input and output of oxygen and water

CO₂ used for photosynthesis and enters through the stomata.

O₂ enters through roots and is a byproduct of photosynthesis.

Exists through the stomata. 

Temperature 

Vegetative Stage: 20-30°C range

Flowering Stage:  18-26°C 

Humidity

• Clones 70%
• Vegetative 40-60%
• Flowering 40-50%
• Final weeks of flowering 40-45%

Additional CO₂ 

The more light intensity the more CO₂ cannabis plants need. Cannabis Can Use Up to 1500 PPM  CO₂  increasing CO₂  concentrations can increase yield. Only growers who benefit from added CO₂ are those who desire quicker yields. 

Airflow

Always make sure to have air circulation around the plant.

Do not point the fan directly on your plants.

Water and Nutrients 

Water is used for photosynthesis, transpiration and mineral uptake

Water polarity and ph are vital for nutrient uptake.

Watering Cannabis

Watering less often and thoroughly is better than giving your cannabis a little water often.

Make sure to drench the entire medium completely.

Know that slightly underwatering your plants is always better than overwatering as it encourages root formation. 

Primary Minerals 

Cannabis essentially needs 13 minerals for growth

N,P,K,Ca,Mg,S,Fe,B,Zn,Cu, Mn, Mo, Cl

Macro-Nutrients 

Nitrogen, Phosphorus, Potassium (NPK)

Secondary and Nonessential Nutrients

Needed for plant actions and play i vital roll in cannabis’ life cycle.

Deficiency and Toxicity 

Mobile Deficiency shows on the older leaves first.

N,Mg Ni

Imobile Deficiency growth moves from the roots to final location start at the news growth. 

B, Ca, Mg, Fe, Cu, Fe, Zn

Nutrient Schedule

Vegetative Stage

N – P – K

3 – 1 – 2

Flowering Stage

N – P – K

1 – 1 – 2

Final Flowering Stage

N – P – K

0 – 1 – 2

Reduce Nitrogen two weeks after flipping 12/12 light schedule will assist in stopping the vertical growth (stretch) and result in a less leafy, smoother burning, and denser end product. 

Phytohormones

Primary hormones and their function phytochrome

Auxins responsible for cell direction and elongation

Cytokinin works with Auxins and is needed for cell division 

Gibberellins tigres seed to germinate

Ethylene in gaseous form make the responsible for maturation/calyx close up in cannabis

Abscisic protects plant from drought signals the stoma to close 

Florigen signals start of flowering

We can generally categorise the individual phytohormones as working to either promote, inhibit or otherwise affect growth in one way or another.

With correct genetics and epigenetic conditions, a typical grow does not need phytohormone intervention.

Mycorrhizal

Forms a symbiotic association between cannabis and a fungus. The plant makes organic molecules such as sugars by photosynthesis and supplies them to the fungus, and the fungus supplies to the plant water and mineral nutrients from the soil.

In addition to soil medium, cannabis can be grown in water. Lately new gel growing mediums have been developed that automates the growing process. In addition, automated growing tents help have tighter control while growing.

These are guidelines to help you grow your first cannabis harvest. Like any other science, botany consists of experimentation. 

Do not get discouraged, help shape future cannabis genetics. We love to hear your favorite growing techniques.