Auxins vs Cytokinins in Cannabis
Quick Summary: Auxins drive vertical stretching and root depth, while cytokinins trigger cell division for bushier, lateral growth. Mastering the auxins vs cytokinins cannabis balance allows growers to manipulate plant structure, maximize light penetration (PAR), and significantly boost final flower yields.
Auxins vs Cytokinins in Cannabis Development
Auxins and cytokinins are the “brain” of your cannabis plant. These tiny chemical messengers decide if your plant grows like a tall pine tree or a wide, bushy hedge. In the world of high-end cultivation, understanding the difference between auxin and cytokinin is what separates a hobbyist from a master grower. These phytohormones work in a constant tug-of-war known as apical dominance.
Recommended Strains
Gelato Auto
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THC | 19% - 21% (Medium) |
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Type | Autoflowering |
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Yield | Medium |
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Phenotype | 40% Indica / 60% Sativa |
Ghost Train Power
|
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THC | 28% - 30% (High) |
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Type | Feminized |
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Yield | High |
|
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Phenotype | 20% Indica / 80% Sativa |
Auxins are made in the terminal buds (the very top). they flow downward, telling the plant to focus on reaching for the light. This vertical drive is great for deep root establishment but can lead to “lanky” plants if not managed. Cytokinins, conversely, are primarily synthesized in the roots and move upward. They are the masters of cell division, telling the plant to grow more side branches and larger leaves, which is vital for a high-surface-area canopy.
Promos & Deals
Auxins: The Master of Verticality and Rooting
Auxins, specifically Indole-3-butyric acid (IBA) and Naphthaleneacetic acid (NAA), are essential during the early stages of life. When you take a cutting from a mother plant, auxins migrate to the wound to initiate root primordia. This is why most rooting gels contain high concentrations of these hormones. Without them, your clones would never develop the vascular system needed to transport water and nutrients.
In a growing plant, auxins suppress the growth of lateral buds. This is why the main “cola” is always the largest. If you want a tall plant to fill a high-ceiling grow room, you want to maintain high auxin levels. However, too much auxin can cause a lack of airflow between branches, increasing the risk of Botrytis (bud rot) due to high humidity levels trapped in the dense, vertical foliage.
Cytokinins: The Secret to a Bushy Canopy
If auxins are the “gas” for height, cytokinins are the “gas” for width. They promote the growth of lateral buds, effectively breaking the apical dominance held by the main tip. By increasing the ratio of cytokinins and auxins, you encourage the plant to develop a flat, even canopy. This is the goal of techniques like the Sea of Green (SOG) or Screen of Green (SCROG), where every bud site receives equal PPFD (Photosynthetic Photon Flux Density).
Biologically, cytokinins delay senescence, the aging of leaves. By keeping leaves green and metabolically active for longer, the plant can continue to produce carbohydrates through photosynthesis deep into the flowering phase. This leads to denser buds and a complex terpene profile, as the plant has more energy to spend on secondary metabolites like Limonene and Myrcene.
Technical Comparison: Hormone Influence on Plant Architecture
| Feature | High Auxin Ratio (Sativa-Dominant) | High Cytokinin Ratio (Indica-Dominant) |
|---|---|---|
| Growth Direction | Vertical / Apical Dominance | Lateral / Bushy branching |
| Cellular Action | Cell Elongation (stretching) | Cell Division (multiplication) |
| Root Impact | Deep taproot development | Fibrous, dense root mass |
| Flowering Effect | Often delays transition to bloom | Promotes faster bud set |
| Ideal Environment | Large outdoor spaces / High ceilings | Limited indoor height / Tents |
| Training Synergy | LST (Low Stress Training) | Topping / FIMming |
How to Strategically Manipulate Hormones for Yield
The most common way to change the auxins vs cytokinins cannabis balance is through physical training. When you “top” a plant, you remove the primary source of auxins. This sudden drop allows cytokinins from the roots to rush to the lower nodes, causing them to explode with new growth. This creates two or more main colas instead of one, effectively doubling your high-quality flower sites.
For Sativa strains like Power Plant or Amnesia Haze, managing this balance is critical. These strains naturally produce high levels of auxins, which can cause them to grow too close to your HID or LED lights, leading to light burn. By encouraging cytokinin production through topping or light stress, you keep the plant at a manageable height while increasing the “frostiness” of the lower buds.
Professional Cultivation Tips
- Fresh Natural Extracts: Teas made from nettle, thyme, or garlic are rich in natural phytohormones. However, these must be used the same day they are brewed, as the living hormones degrade rapidly once exposed to air and light.
- Foliar Efficiency: Cytokinins are highly effective when applied via foliar spray. This bypasses the root system and delivers the hormone directly to the leaf tissue, which is perfect for reviving a mother plant that has been over-cloned.
- The “Once a Month” Rule: Never over-apply hormone supplements. Excess hormones can confuse the plant’s DNA, leading to mutations or hermaphroditism. A single application once a month is usually the “sweet spot” for healthy growth.
- Bottom Heat for Auxins: Keeping your growing medium at 75-80°F (24-27°C) stimulates root-based hormone activity, significantly speeding up the rooting of clones that rely on auxin signals.
How do auxins and cytokinins affect cannabis yields?
Yield is determined by the number of productive bud sites and the density of the flowers. Auxins increase the size of the plant’s “frame,” while cytokinins ensure that frame is filled with branches. A plant with a high cytokinin-to-auxin ratio during the vegetative stage will have more nodes, leading to more colas and a significantly higher dry weight at harvest.
Can I manipulate auxins and cytokinins naturally?
Absolutely. Physical training like Topping, FIMming, and LST (Low Stress Training) are natural ways to redirect hormone flow. Environmental factors like light spectrum also play a role; blue light (5000K-6500K) tends to favor cytokinin-like bushy growth, while far-red light can trigger the “shade avoidance response,” which is an auxin-driven stretch.
What are the risks of using synthetic hormone supplements?
The primary risk is hormonal toxicity. If you apply too much IBA or synthetic cytokinins, the plant may experience “stunted growth syndrome” where the cells stop dividing altogether. Always start with a quarter-strength dose and monitor the leaf tips for “clawing” or unusual twisting, which are signs of hormonal stress.
