How to Grow Cannabis: The Cultivator's Guide to Mastering the Fundamentals of Growth

As a nutrient company founded by growers, Athena understands that successful cannabis cultivation depends on a solid grasp of horticultural fundamentals. This comprehensive guide will explain exactly how to grow cannabis from start to finish, covering every stage of the life cycle. This guide serves as your foundation—providing clear, unbiased, and instructional insights into cannabis production. We move beyond marketing noise to focus on the science that drives consistent, repeatable results. Our approach is peer-to-peer, sharing real-world best practices with the knowledgeable, straightforward voice of an experienced head grower."

Understanding the Five Core Cultivation Principles

Before diving into step-by-step instructions, it is vital to grasp the hierarchy of factors that determine your plant’s success. These principles act as limiting factors, meaning subsequent factors can only maximize potential if the preceding ones are optimized.

1. Genetics (Blueprint): Genetics form the foundation, shaping potential yield, flavor, and potency. The plant’s overall potential hinges on this blueprint.
2. Lighting (Engine): Proper lighting, including intensity, duration, and spectrum, is crucial for plant development.
3. Environment (Health): A stable environment—managing temperature, humidity, and air circulation—is key to ensuring plant health and high-quality buds.
4. Grower (Execution): The grower's knowledge and attention to detail, making timely adjustments based on plant needs, ensures optimal growth and yield.
5. Nutrients (Fuel): Nutrients are crucial for boosting yield, but only when the other four factors (Genetics, Lighting, Environment, and Grower skill) are already optimized.

Pillar 1: Starting Your Run - Seed vs. Clone

Understanding where your plant begins is fundamental.

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If starting with clones, always quarantine, clean, and dip them in an Integrated Pest Management (IPM) solution. Check for bugs and ensure the cutting is healthy before introducing it to the main grow area.

Pillar 2: Mastering the Light

Light is the fuel for photosynthesis and must be precisely managed throughout the cannabis life cycle.

Light Spectrum and Cycles

Cannabis utilizes specific light cycles to regulate its growth stages (Clone, Veg, Flower, Finish).

• Blue Light: Promotes strong, compact Vegetative growth, mimicking Spring/Summer conditions. Used during the Clone (24 hours on) and Veg phases (18 hours on / 6 hours off).
• Red Light: Critical for triggering the Flower phase, enhancing bud development and resin production, mimicking Summer/Fall conditions. Used during the Flower and Finish phases (12 hours on / 12 hours off).

Measuring Light Intensity (PAR and PPFD)

Plants use light in the 400–700 nm range, known as Photosynthetically Active Radiation (PAR). The intensity of this light reaching the plant is measured in Photosynthetic Photon Flux Density (PPFD).

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Grower Tip: Lights placed too close to the flower buds may cause bleaching. Plants can double in size after the light cycle flip (veg to flower), so adjust light placement accordingly.

Pillar 3: Environmental Control and Substrates

A stable climate is vital, as fluctuations can lead to stunted growth, disease, or death.

Vapor Pressure Deficit (VPD) Explained

VPD is a measurement reflecting the moisture difference between the air and the leaves, directly influencing plant transpiration. Maintaining the ideal VPD promotes healthy growth, nutrient uptake, and higher yields.

• Optimal Ranges: VPD is managed by aligning temperature and relative humidity (RH) to the plant’s growth stage. For example, during Veg, optimal indoor temperatures are 72^o F - 82^o F  with RH up to 75%. For Flower, temperatures are 75^o F - 82^o F , and the RH tapers down.
• Danger Zones (Avoid): Conditions outside the optimal VPD range cause stress.
  
  • High Humidity/Low Temp: Risks root rot, poor nutrient uptake, and fungal issues.
  • Low Humidity/High Temp: Risks heat stress, dehydration, and stunted growth.

Choosing Your Substrate

The medium where plants grow (like coco, rockwool, or DWC) is known as the substrate.

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Substrate Size and Watering: Smaller pots require more frequent watering (daily) to prevent excessive drybacks. Larger pots retain more water and reduce watering frequency, which can help align with your schedule.

Pillar 4: Precision Nutrient Management

Nutrients are the fuel, but they must be provided consistently and accurately.

Starting with Clean Water

Begin with Reverse Osmosis (RO) water whenever possible, as it is a clean, impurity-free base that supports nutrient uptake. RO water should have a starting EC close to 0.0. If using tap water, ensure its Electrical Conductivity (EC) is below 1.0; otherwise, the mineral imbalance may lead to nutrient deficiencies.

Understanding EC and pH

• EC (Electrical Conductivity): This measures the concentration of nutrients in your feed water (Feed EC) or drained water (Runoff EC). Maintaining the right EC ensures plants receive the appropriate concentration of nutrients. The Feed EC will gradually increase over the life cycle before decreasing towards the Finish phase.
• pH: This measures how acidic or basic a solution is. pH is crucial because it affects the availability of nutrients in the growing medium. For coco/rockwool substrates, the target pH range for feeding is typically 5.8–6.2.

Nutrient Mixing Best Practices

When using a professional cultivation-focused nutrient system (such as the Athena Blended Program which uses multiple parts like Grow A/B, Bloom A/B, and additives like PK and CaMg):

1. Fill your reservoir with RO water.
2. Add nutrients in the specified order, mixing slowly and thoroughly between adding each part.
3. Check the EC using an EC meter to ensure it matches the target value for that week. Adjust by adding more nutrients (if under target) or RO water (if over target).
4. Check and adjust the pH using a product like Balance (to raise pH) or pH Down (if needed) to maintain the optimal range.

WARNING: Incorrect mixing order may cause precipitation and lead to batch failure.

Crop Steering: Vegetative vs. Generative Growth

Crop steering is a technique used to control plant growth by adjusting irrigation, dryback, and substrate EC to focus on specific growth goals.

Dryback Explained: The dryback is the period between feedings when the substrate is drying out. The extent of the dryback determines the substrate EC, influencing the plant’s growth response.

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Grower Tip: Never dry back to the point of wilting, as this can affect yield, harvest quality, and potentially kill your plants.

Pillar 5: Grower Techniques and Maintenance

The grower is responsible for implementing care, training, and maintenance. A consistent routine is critical.

Daily Grower Checklist Highlights:

• Check RO system output and record temperature/humidity twice daily.
• Ensure airflow to prevent hotspots and mildew.
• Confirm pH of irrigation water and nutrients.
• Check runoff pH for root zone consistency.
• Inspect for pests or mildew and act quickly.
• Monitor plant height and inspect for light leaks during dark periods.

Key Training Techniques

• Low Stress Training (LST): Bending and tying branches to enhance light distribution, ensure even growth, and boost yield with minimal stress. Trellising (weaving plants through a support structure) helps create an even canopy and improves airflow.
• Topping: Removing the main growth tip (snipping the newest growth) to redirect energy to side branches, promoting bushier growth and maximizing canopy potential. Best performed early in the vegetative stage.
• Deleafing and Lollipopping (Flower Phase):
  
  • Deleafing: Removing large fan leaves that block light to the lower canopy to improve light penetration and encourage bud sites to mature evenly.
  • Lollipopping: Removing small leaves and underdeveloped bud sites below the trellis. This prevents "larf" (low-quality, airy buds) and redirects energy to the main colas for denser, higher-quality buds.

Integrated Pest Management (IPM)

Pest management requires vigilance, maintaining a sterile environment, and monitoring closely. IPM programs involve preventative sprays (like using an insecticide/fungicide product) typically two times per week during Veg and early Flower (Weeks 1–3).

WARNING: Never spray IPM on plants unless the media is wet and the lights are off. Do not use IPM after Week 3 of Flower.

Step-by-Step Cultivation Phases

The cannabis life cycle progresses through distinct phases, each with specific requirements:

1. Seed/Clone (Approx. 2 Weeks): Focus on germination or clone inspection, strong root development, and maintaining high humidity. For seeds, germination can be achieved by soaking them in a moist, pH-adjusted paper towel and placing them in a warm, dark place. Transplant once a 2-inch root develops. For clones, inspection, dipping in a rooting gel, and monitoring for pests are critical.
   
   • Climate: High temperature (75^o - 80^o F) and high RH (65–75%).
2. Vegetative (Approx. 4 Weeks): Plants develop strong structural components (stems and leaves). This phase is managed using a Vegetative irrigation strategy (higher runoff, shorter drybacks, low runoff EC). Canopy management (LST, topping) is performed here.
   
   • Climate: High temperature (72^o - 82^o F) and high RH (58–75%).
3. Flower (Approx. 7 Weeks): Energy shifts to bud production. Early flower (W1–4) uses a Generative irrigation strategy (less runoff, longer drybacks, stacking EC) to promote flower site formation. Later flower (W5–7) shifts back to a Vegetative strategy (higher runoff, lower substrate EC) to promote bud swelling. Deleafing and Lollipopping occur around Week 3.
   
   • Climate: Temperature 75^o - 82^o F , gradually lowering RH (60–72%).
4. Finish (Approx. 2 Weeks): The goal is to flush out excess nutrients, encouraging the plant to express its full genetic potential, which improves flavor, aroma, and smoke quality. Tapering nutrients down and running high runoff flushes the media.
   
   • Climate: Taper temperatures down (to 65^o - 72^o F) and maintain lower RH (50–60%).
5. Dry/Cure (Approx. 4 Weeks): The final step for quality. Dry until stems snap and buds feel dry to the touch (approx. 12–14 days). Then, buds are cut and placed into jars/containers (70% full). The curing process involves "burping" (opening the lid for 10–15 minutes, 1–2 times daily for about two weeks) until the bud humidity reaches 58–62%.
   
   • Harvest Timing: Inspect trichomes with a microscope. The plant is ready when the trichomes are approximately 90% amber.
   • Drying Climate: 60^o - 65^o F and 55–60% RH.

The Final Step: Reset and Sanitation

After harvest, sanitation is non-negotiable to eliminate pathogens. Follow procedures between crop cycles to ensure you start clean every time, using a solution like bleach to clean and disinfect tables, floors, trellis, and all hard surfaces. Always wear proper PPE during sanitation.

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