Cannabis Anatomy
- Understanding the anatomy of a cannabis plant is critical to a successful garden.
- Throughout this course and the rest of the CCS curriculum, very specific plant parts will be repeatedly referenced for various tasks and observations.
- Taking the time to study and memorize these parts will pay off. We’ll start with a female vegetative plant:
Leaflet Anatomy
Now, let’s look at an individual finger (leaflet) of a cannabis fan leaf.
- Veins are easily visible and transport water and nutrients throughout the plant.
- The leafy tissue between the veins is referred to as the intervein. Discoloration at the intervein can be a sign of nutrient deficiency.
- The very outside edge all the way around any leaf is referred to as a margin. Discoloration of the margin can be a sign of nutrient burn.
- The serration is the toothy edge of the leaf.
Genetics
- The very first step in growing outstanding cannabis is to choose the right seeds with strong genetics.
- A plant’s genetic code, or genotype, is a stored set of responses to environmental triggers. These triggers include just about every aspect of the environment — light/shade, water/drought, gravity, temperature, nutrients, and many more.
- We want plants that are less likely to express negative traits, such as hermaphroditism, yet are very likely to express beneficial traits, like dense buds, or a certain terpene profile. Genetic expression in response to the environment is called phenotype.
- Quality breeders select plants with desirable traits, and breed them for many generation, culling out the less desirable specimens. This is how stable strains are produced.
- Quality growers provide the best environment for triggering the best phenotype.
Sativas
- Selecting the strain that’s right for your is very important, and there are a lot of considerations.
- Landrace strains that evolved near the equator are called Sativa. The terpene profile is often described as tropical, citrus or spicy. These plants tend to grow taller with narrow leaflets.
- E.g. Durban Poison, Thai, Acapulco Gold
Indicas
- Those that evolved in the eastern mountains, are known as Indica. The terpene profile emits natural, floral, piney, and earthy aromas. They have a sedative euphoric cannabinoid profile. These plants tend to grow squat with broad leaflets.
- E.g. Afghani, Hindu Kush, Pakistan Valley Kush
Hybrids
- Over that last several decades breeders have crossed landrace cultivars to produce new hybrids with unique properties. When done properly, these hybrids can bring the best traits from different strains to the garden.
- A great example of this is the cultivar known as Girl Scout Cookies and is the product of Durban Poison and Hindu Kush. This stable hybrid has a sweet smell reminiscent of cookies, and is very different from either of its landrace parents.
- Stable and resilient hybrids can be a great addition to any garden.
- On the flip side, breeders who take shortcuts and breed hybrids of hybrids (known as polyhybrids) without first stabilizing the cultivar, are creating a recipe for disaster. Whenever genetics are crossed, new and sometimes unpredictable anomalies occur, and these anomalies can be recessive. This means they might not present themselves until they are already in the grower’s garden.
Reputable Seeds Banks/Breeders
- Sensi Seeds
- Aficionado Seeds
- Top Dawg Seeds
- Brothers Grimm Seeds
- Seedsman
- Nirvana
Germination
When seeds are exposed to prolonged moisture and a warm climate, growth is triggered (spring-like conditions).Preferred Method:
- Place seed in moistened starter block (rockwool/peat).
- Place starter block in a tray of about ½ inch of standing water. Maintain this level of water throughout germination.
- Add only beneficial bacteria (bacillus) to the water. Do not use nutrients at this stage.
- The starter plugs will wick up and maintain an appropriate amount of moisture for your seedlings.
Common germination issues
Seedling are very susceptible to rot at the base of their shoot. This is known as “damping off,”Damping off can be easily avoided if the plant is never over-watered, and the soil drains properly.
- Water should never collect at the base of the shoot, and the soil should not seem “muddy,” but instead should appear damp.
- In hydroponics, sufficiently oxygenating the water will prevent damping off. This is usually accomplished by using large air stones.
It is also important to look for hypocotyl shoot elongation (etiolation) or the formation of an apical hook in response to too little light. This growth is controlled by the amount of light received by the photoreceptors (phytochromes and cryptochromes) within the hypocotyl shoot (C. Lin, 2000).
Left is a healthy seedling. Right is an etiolated seedling with the formation of an apical hook.
Left is a healthy seedling. Right is an etiolated seedling with the formation of an apical hook.
Germination Timeline
- On day 1 or 2, the tap root will emerge.
- On day 2 to 4, the hypocotyl shoot will push the seed above the ground.
- On day 3 to 5 the embryonic set of leaves (cotyledons) within the seed will begin to swell and rapidly grow which will shed the seed husk.
- Day 4 – 7: The first set of serrated leaves will appear. Germination is complete. Begin seedling care!
- At around day 10, or when the second set of serrated leave just begin forming: Your seedling is ready for transplanting to the grow medium.
- For coco and hydroponics: The seedling can begin accepting around ¼ strength of a light nutrient fertilizer.
- The seedling is ready for vegetative lighting.
Juvenile Vegetation
This stage only occurs when growing from seed.
- Last 2-4 weeks after germination.
Vigorous growth of vegetation:
- Branching
- Foliage
- No sex organs
Sinsemilla
No males allowed! Large resin-rich buds like this are achieved by preventing pollination.
- Sinsemilla is a term used among cannabis growers to describe a garden consisting of only unpollinated female flowers.
- Unpollinated female flowers are far more desirable for a number of reasons:
- Less seed weight in a final product
- Unfertilized female flowers tend to grow larger
- Unfertilized female flowers tend to have a higher trichome concentration
Determining Sex
This male plant has already begun to develop its pollen sacs.
Early male sex organs tend to point outward or downward and are attached by a very small stem. In later stages they form clusters. In very late stage these organs open up and disperse the contained pollen. Male plants do not produce resinous flowers. Pollen induces female fruiting (seed formation), and the males should be culled from the crop before this happens.
- Begin to show via pre-flowers after about 4-6 weeks.
- Usually appear first at axillary sites that have begun branching.
- Male plants do not produce buds, and should be culled from the crop.
Female pre-flowers like the ones pictures above can look like male parts when they first begin forming. The primary difference is that they tend to point upwards early on. A sure determination is made once the two tell-tale white colored hair-like styles emerge.
Cannabis Sex Organs
- A male flower in bloom
- & 3. Pollen sac from various angles
- pollen grain
- female flower with cover petal
- female flower, cover petal removed
- female fruit cluster, longitudinal section
- fruit with cover petal
- same without cover petal
- same, mature, side view
- same in cross-section
- same in longitudinal section
- seed without hull
Cloning
- Cloning is considered a best practice for many reasons.
- Once a grower has found a plant that grows well, it is a good idea to clone it. A clone is an exact genetic copy, so it should grow very similarly in a similar environment.
- Clones will also be the same gender as the parent, saving growers time and energy. No more culling males!
- Clones retain the maturity of their mothers, skipping the juvenile vegetative stage altogether.
- As soon as a clone takes root, it begin adult vegetation, and is ready to flower any time.
Using an aeroponic system, these healthy roots emerged in 12 days. Once planted, this clone will begin canopy growth within a few days.
Taking clones:
- Cuttings should be taken from a vegetative plant. Cuttings should be from pliable branches, and should have several axillary nodes.
- Fresh cuttings should be immediately placed in water until they can be further handled.
- Because cuttings have no roots, they are unable to uptake water as quickly as a leafy canopy can transpire it. Reducing the overall canopy surface area can greatly reduce wilting resulting in healthier clones.
- This should be done by pruning away large fan leaves or by reducing them in size by clipping the finger leaflets.
Optional Cloning Steps
Make 2 to 4 evenly spaced ¼” to ½” lines at end of the stalk by lightly scratching only the outermost layer (epidermal) with the tip of your razor knife.
Slice the end of your stalk with a razor knife at a 45 degree angle, including the newly scratched lines with the cutting.
Dip the end of the stalk in Clone-X, ensuring to fully submerge the scratch marks.
Cloning Tips
- For best results, cuttings should be kept in a warm and humid environment. Humidity domes or plastic bags work best.
- Cuttings from a flowering plant take much longer to root and will grow oddly for a short time as they revert to vegetative growth. Success rates can be negatively impacted.
- Larger cuttings tend to root faster than smaller cuttings.
- Cuttings with “woody” shoots generally take longer to root than cuttings with pliable shoots.
- Rooting hormones such as CloneX may help with success rates.
- Scratching the outermost layer of the shoot (epidermis) in very small areas may help roots emerge from within the meristem.
- Aeroponic and Hydroponic systems can help cuttings root even faster
Hands on Practice Time!
Practice Cloning
- Identify a viable cutting
- Take a cutting
- Prepare cutting for rooting
- Provide the right environment for the clone