Vapor Pressure Deficit (VPD)

Vapor Pressure Deficit (VPD) is a critical concept in cannabis cultivation, as it directly impacts plant transpiration, nutrient uptake, and overall growth. Here’s a breakdown of what VPD is and how it relates to growing cannabis:

What is VPD?

VPD measures the difference between the amount of moisture in the air and the air’s moisture-holding capacity at a given temperature. It combines humidity and temperature into one metric and is expressed in kilopascals (kPa).
• Low VPD: Indicates high relative humidity and low evaporation potential. Plants transpire less, which can lead to waterlogging and poor nutrient uptake.
• High VPD: Indicates low relative humidity and high evaporation potential. Plants transpire more, which can cause dehydration and stress.

Why is VPD Important for Cannabis?
1. Optimized Transpiration:
• Transpiration is how plants regulate water and nutrient uptake.
• Proper VPD ensures plants transpire at an optimal rate, promoting healthy growth.
2. Photosynthesis Efficiency:
• VPD affects stomata opening. When VPD is balanced, stomata remain open, allowing for efficient gas exchange (CO₂ intake and oxygen release).
3. Pest and Mold Prevention:
• Incorrect VPD (too low or too high) can create conditions favorable for pests, mold, and mildew.
4. Stress Reduction:
• A proper VPD minimizes stress, ensuring the plants allocate energy to growth and cannabinoid production rather than survival.

Ideal VPD for Cannabis

The ideal VPD depends on the growth stage:

Stage Temperature (°F) Relative Humidity (%) VPD Range (kPa)
Seedling/Clone 70–75 65–70 0.4–0.8
Vegetative 75–85 55–65 0.8–1.2
Flowering 70–80 40–50 1.2–1.6

How to Adjust VPD
1. Increase VPD:
• Lower relative humidity.
• Increase temperature.
2. Decrease VPD:
• Increase relative humidity.
• Lower temperature.
3. Tools to Monitor/Control:
• Use a hygrometer and thermometer to measure humidity and temperature.
• Employ humidifiers, dehumidifiers, and heaters/coolers to adjust conditions.

By maintaining optimal VPD throughout the cannabis lifecycle, you can significantly improve plant health, yield, and cannabinoid production.

Hugelkultur

Using wood as a soil amendment is a concept often associated with hugelkultur (German for “mound culture”). This technique involves incorporating woody materials into the soil to improve fertility, moisture retention, and microbial activity. Here’s how wood can be effectively used in soil and the benefits it provides:

Hugelkultur Basics
1. What It Is:
Hugelkultur involves building raised garden beds or mounds by layering wood (logs, branches, twigs), organic matter, and soil. The wood decomposes over time, enriching the soil.
2. How to Build a Hugelkultur Bed:
• Start with a base layer of logs, branches, or other woody materials.
• Add smaller branches, twigs, or wood chips.
• Layer with organic materials like leaves, grass clippings, and compost.
• Cover with soil (6-12 inches thick) to create a planting layer.

Benefits of Using Wood in Soil
1. Moisture Retention:
Decomposing wood acts like a sponge, absorbing and releasing water, reducing the need for frequent irrigation.
2. Nutrient Cycling:
As wood breaks down, it slowly releases nutrients like nitrogen, phosphorus, and potassium, improving soil fertility.
3. Improved Soil Structure:
The porous nature of decomposing wood enhances aeration and drainage in heavy soils while retaining moisture in sandy soils.
4. Microbial Habitat:
Decomposing wood provides a home for beneficial soil microbes and fungi, promoting a healthy soil ecosystem.

Considerations When Using Wood in Soil
1. Nitrogen Drawdown:
Fresh wood (especially high-carbon materials) may temporarily deplete soil nitrogen as microbes use it for decomposition. To counteract this, add nitrogen-rich materials (e.g., green plant matter, manure) or compost to balance the carbon-to-nitrogen ratio.
2. Wood Type:
• Good Choices: Hardwood (oak, maple), softwood (pine, spruce), and fruit tree wood.
• Avoid: Treated, painted, or chemically-treated wood, which can leach harmful substances into the soil.
3. Size of Wood Pieces:
Larger logs decompose more slowly, providing long-term benefits. Smaller wood pieces or wood chips break down faster, giving quicker results but requiring more frequent replenishment.

Alternative Uses of Wood in Soil
1. Wood Chips as Mulch:
Spread wood chips on the surface to suppress weeds, retain moisture, and slowly add organic matter to the soil.
2. Biochar:
Charred wood (biochar) can be added to soil to improve its ability to retain nutrients and water while reducing nutrient leaching.
3. Woody Composting:
Mix small wood pieces into a compost pile to create a balanced, nutrient-rich soil amendment.

Using wood as a soil amendment through hugelkultur or other methods is a sustainable and effective way to enhance garden productivity, especially in areas with poor or depleted soils.

Integrated pest management

Beneficial insects play an essential role in integrated pest management (IPM) for cannabis cultivation. They help control pests naturally, reducing the need for chemical pesticides. Here’s a list of beneficial insects commonly used in cannabis growing:

Predatory Insects
1. Ladybugs (Hippodamia convergens)
• Feed on aphids, whiteflies, and spider mites.
• Particularly effective during the early stages of infestations.
2. Lacewings (Chrysoperla spp.)
• Larvae are voracious predators of aphids, thrips, and mealybugs.
3. Praying Mantises (Tenodera sinensis)
• Generalist predators that consume a wide variety of pests, including caterpillars and beetles.
4. Predatory Mites (e.g., Phytoseiulus persimilis, Amblyseius swirskii)
• Control spider mites, thrips, and whiteflies.
• Amblyseius swirskii is particularly useful in warm, humid conditions.
5. Minute Pirate Bugs (Orius spp.)
• Prey on thrips, aphids, and small caterpillars.

Parasitic Insects
1. Parasitic Wasps (e.g., Encarsia formosa, Aphidius colemani)
• Target specific pests like whiteflies and aphids by laying eggs inside them.
2. Nematodes (e.g., Steinernema feltiae)
• Soil-dwelling organisms that control fungus gnats and root-dwelling pests.

Soil Beneficials
1. Rove Beetles (Dalotia coriaria)
• Feed on fungus gnats, thrips pupae, and other soil-dwelling pests.
2. Hypoaspis Mites (Stratiolaelaps scimitus)
• Effective against fungus gnats and thrips in the soil.

Benefits of Using Beneficial Insects
• Eco-Friendly: Reduces reliance on chemical pesticides.
• Pest-Specific: Targets pests without harming plants or beneficial organisms.
• Sustainable: Supports a balanced ecosystem within the grow environment.

Tips for Success
1. Early Introduction: Release beneficial insects at the first sign of pests or as a preventive measure.
2. Environmental Conditions: Maintain optimal humidity, temperature, and lighting conditions for the insects.
3. Avoid Pesticides: Minimize or eliminate pesticide use, as it can harm beneficial insects.
4. Monitor Populations: Regularly check pest and predator populations to ensure effectiveness.

Implementing beneficial insects as part of your IPM strategy can greatly improve plant health and yield in cannabis cultivation.

Ultra violet light effects on cannabis thc production

Ultraviolet (UV) light can influence the production of secondary metabolites in plants, including THC (tetrahydrocannabinol) in cannabis. Here’s a detailed overview of how UV light, particularly UV-B and UV-A, affects cannabis THC production:

1. Role of UV Light in THC Production
• UV-B Radiation: Studies suggest that exposure to UV-B light can stimulate the production of THC in cannabis plants. THC acts as a protective compound, shielding the plant from UV radiation. UV-B stress triggers the plant to produce more trichomes (resin glands) where THC is synthesized.
• UV-A Radiation: While less energetic than UV-B, UV-A can also contribute to trichome development and secondary metabolite production, though its effects are generally less pronounced than UV-B.

2. Mechanism
• Stress Response: Cannabis plants produce THC as part of their defense mechanism against environmental stressors, including UV radiation.
• Gene Activation: UV light activates specific genes responsible for synthesizing THC and other cannabinoids, as well as terpenes, enhancing the overall resin production.

3. Optimal Exposure
• Moderate exposure to UV-B light during the flowering stage can enhance THC levels. Overexposure, however, can damage the plant’s cells and negatively impact overall health and yield.
• Controlled UV light supplementation in indoor or greenhouse cultivation can be particularly effective, as natural UV exposure may be inconsistent.

4. Factors Influencing UV Effects
• Plant Genetics: Some cannabis strains are more responsive to UV light than others due to their genetic predisposition for cannabinoid production.
• Intensity and Duration: The amount of UV exposure (intensity and time) plays a critical role in determining its effects.
• Growth Environment: Indoor and greenhouse growers can fine-tune UV light exposure to maximize THC production without damaging plants.

5. Practical Applications
• UV-B lamps are often used in indoor cultivation setups to mimic natural UV exposure and stimulate THC production during the flowering stage.
• Outdoor growers in regions with high UV levels (e.g., high altitudes or near the equator) often observe naturally higher THC levels in their plants.

6. Considerations and Risks
• Prolonged UV exposure can cause photodamage to plants, including leaf burn and reduced photosynthesis.
• Proper protective equipment should be used when working around UV light to avoid harm to human skin and eyes.

Fem seeds

I get asked all the time about this. And yes I plan to offer them soon as I’m happy with my work on that.
Why can I offer no eta?
That’s simply impossible. My strains have over a decade in to stabilizing them to resist herm.
So to even get them to try to flip often requires more than sts spray for me . And then I require extensive testing on that output . To ensure the herm resistance carries over to the fem line.
This is honestly something new for me because I have for decades been a anti fem- hermie seed guy..

Curing Cannabis for optimal flavor

Curing cannabis properly enhances its flavor, aroma, potency, and smoothness. Here’s a step-by-step guide to curing cannabis for the best results:

1. Preparation
• Ensure your buds are properly dried. Buds should feel dry on the outside, and smaller stems should snap instead of bending. However, the larger stems may still retain some flexibility.
• Gather airtight containers, such as glass jars, ceramic jars, or specialized curing containers.

2. Fill the Containers
• Loosely pack the jars: Fill jars about ¾ full to allow airflow while minimizing empty space. Overpacking can lead to uneven curing or mold growth.
• Avoid crushing the buds, as this can damage trichomes.

3. Initial Burping Phase (First 1-2 Weeks)
• Seal the jars: Close the containers to trap moisture and allow the curing process to begin.
• Burp daily: Open the jars for 5–15 minutes once or twice a day to release excess moisture and replace stale air with fresh air. This also prevents mold.
• Inspect for signs of mold or overly damp buds during this phase. If buds feel too moist, leave the jar open longer to dry slightly.

4. Long-Term Curing (Weeks 3-8 or Longer)
• After the first 1–2 weeks, reduce the burping frequency to once every few days.
• Over time, the moisture inside the buds will redistribute evenly, enhancing the flavor and aroma.

5. Monitoring Humidity
• Use small hygrometers inside jars to monitor relative humidity.
• Optimal range: 58–62% RH.
• If RH exceeds 65%, open the jar to let moisture escape or add a humidity control packet (e.g., Boveda packs).
• If RH drops below 55%, the buds may overdry and lose quality. Rehydrate carefully using humidity packs.

6. Taste Testing
• After 2–4 weeks, you’ll notice improved flavor and aroma. However, a longer cure (4–8 weeks or more) often results in richer, more complex profiles.

7. Storage
• Once cured, keep jars sealed in a cool, dark place to preserve terpenes and potency. Avoid exposing the buds to direct light, heat, or fluctuations in humidity.

Properly cured cannabis provides a smooth, flavorful smoke or vapor, with terpenes and cannabinoids preserved at their best.

Drying cannabis in preparation for curing

Drying cannabis is a critical step before curing to preserve flavor, potency, and overall quality. Here’s a guide to properly dry cannabis:

1. Harvesting
• Trim away large fan leaves but leave sugar leaves intact, as they help protect the buds during drying.
• Cut branches into manageable sizes or harvest individual buds, depending on your drying space.

2. Prepare the Drying Space
• Temperature: Keep the space at 60-70°F (15-21°C).
• Humidity: Aim for 55-65% relative humidity.
• Airflow: Ensure good air circulation but avoid direct airflow on the buds to prevent uneven drying.
• Darkness: Keep the room dark, as light degrades cannabinoids and terpenes.
• Odor Control: Use carbon filters or air purifiers if needed.

3. Hanging or Racking
• Hanging: Use strings or hangers to suspend branches upside down. This method is ideal for preserving bud structure.
• Racking: Place smaller buds on drying racks lined with mesh for even airflow. Avoid overcrowding.

4. Drying Process
• Duration: Typically 7-10 days, depending on the environment and bud density.
• Check Progress: Test dryness by bending small stems. They should snap rather than bend when the buds are ready.
• Avoid Overdrying: Ensure buds are not brittle, as this can degrade quality.

5. Monitoring
• Use a hygrometer to measure humidity levels.
• Inspect for mold or mildew daily, especially in dense buds.

6. Ready for Curing

Once dried, the buds should feel dry to the touch but retain slight elasticity. At this stage, transfer them to jars or containers for the curing process.

Check out our other tips on curing!

Homemade tea

Making a tea for cannabis cultivation using shellfish, worm castings, and wood ash is an excellent organic approach to provide nutrients and improve soil health. Here’s a guide to preparing it:

Ingredients:
1. Shellfish (e.g., crab or shrimp meal) personally I really like crawfish :
Rich in calcium, phosphorus, and chitin, which supports plant growth and soil health.
2. Worm castings:
High in beneficial microbes and nutrients like nitrogen, phosphorus, and potassium.
3. Wood ash:
Provides potassium and raises soil pH, but use sparingly to avoid over-alkalizing.

Tools:
• A 5-gallon bucket
• Air pump and air stone (optional, for aerobic tea)
• Water (preferably non-chlorinated)
• Cheesecloth or fine mesh bag (optional, for straining)

Instructions:
1. Prepare the Base:
Fill the bucket with 4-5 gallons of non-chlorinated water. Let tap water sit for 24 hours to dechlorinate, or use filtered water.
2. Add the Ingredients:
• Shellfish Meal: Add about 1/2 to 1 cup.
• Worm Castings: Add 1-2 cups.
• Wood Ash: Add 1-2 tablespoons (sparingly, to prevent nutrient imbalance).
3. Aerate (Optional):
Use an air pump and stone to keep the tea aerobic, which encourages beneficial microbial activity.
4. Brew:
Let the mixture steep for 24-48 hours, stirring occasionally if not aerating.
5. Strain and Use:
Strain the tea if necessary and dilute it with water in a 1:1 ratio. Apply it directly to the soil or as a foliar spray.

Tips:
• Test Soil pH: Before adding wood ash, ensure your soil can handle an increase in pH.
• Use Immediately: The tea is most effective when used fresh.
• Avoid Overdoing It: Apply the tea once every 2-3 weeks to prevent nutrient buildup.

This tea will provide essential nutrients, improve microbial life, and promote healthy cannabis growth.

Biochar

Biochar, a carbon-rich material produced through the pyrolysis of organic biomass, offers several benefits when used in cannabis cultivation. Its ability to improve soil health, retain nutrients, and enhance microbial activity makes it an important tool for growers seeking to optimize plant health and yield.

Benefits of Biochar for Cannabis Cultivation

1. Improved Soil Structure
• Biochar enhances soil aeration and water retention, which are crucial for the development of healthy cannabis root systems.
• It provides a stable habitat for beneficial microbes and fungi that support nutrient uptake.

2. Enhanced Nutrient Retention and Availability
• Biochar acts like a sponge, holding onto essential nutrients (like nitrogen, phosphorus, and potassium) and releasing them gradually.
• This reduces nutrient leaching and ensures consistent availability, promoting robust cannabis growth.

3. Increased Microbial Activity
• Biochar’s porous structure creates an ideal environment for beneficial soil microbes.
• These microbes can improve nutrient cycling, enhance root health, and protect against pathogens.

4. pH Regulation
• Cannabis prefers slightly acidic to neutral pH (around 6.0–7.0). Biochar can help buffer soil pH, preventing extreme fluctuations that might stress the plants.

5. Carbon Sequestration and Sustainability
• Biochar helps sequester carbon in the soil, reducing the environmental impact of cannabis cultivation.
• It supports sustainable growing practices by improving soil fertility and reducing the need for chemical fertilizers.

6. Pest and Disease Resistance
• Biochar can suppress soil-borne diseases and pests by promoting a balanced microbial ecosystem.
• This natural disease resistance is especially valuable in organic cannabis cultivation.

7. Increased Yield and Potency
• The combined benefits of improved nutrient management, healthier roots, and optimized soil conditions often lead to higher yields.
• Healthy plants are more likely to produce potent cannabinoids and terpenes.

How to Use Biochar for Cannabis
1. Pre-charging Biochar: Before applying, soak biochar in nutrient-rich solutions like compost tea or organic fertilizers to avoid nutrient lockup in the soil.
2. Mixing with Soil: Incorporate biochar into the soil mix at 5-10% by volume to avoid over-concentration.
3. Composting: Combine biochar with compost to further enhance its microbial benefits.

Conclusion

Using biochar in cannabis cultivation supports healthier plants, higher yields, and more sustainable growing practices. By improving soil fertility, microbial activity, and nutrient efficiency, biochar is a valuable addition to any grower’s toolkit, whether for small-scale or commercial operations.

Germinating

Germinating cannabis seeds using the paper towel method is a simple and effective way to get your seeds to sprout. Here’s a step-by-step guide to ensure proper germination:

What you will need-

  • Cannabis Seeds (Preferably Fresh and Viable
  • 2-4 sheets of paper towels
  • A couple of plates (or a sealable plastic bag)
  • Filter or distilled clean water
  • A warm, dark place (ideal temperature: 70–85°F or 21–29°C)

Getting Started

1. Prepare Your Materials
• Moisten the paper towels with water but avoid soaking them. They should be damp, not dripping.
• Lay one or two sheets of the moist paper towel on a plate.

2. Place the Seeds
• Gently place your cannabis seeds on the paper towel, spacing them apart to avoid tangling roots.
• Cover the seeds with another layer of damp paper towel.

3. Cover with a Plate
• Place the second plate upside down over the first one to create a dark, humid environment.
• Alternatively, place the paper towel inside a sealable plastic bag but leave it slightly open for air circulation.

4. Store in a Warm, Dark Place
• Keep the setup in a location with a consistent temperature between 70–85°F (21–29°C).
• Check on the seeds daily to ensure the paper towels remain moist. Add a small amount of water if they begin to dry out.

5. Wait for Germination
• Within 24–72 hours, the seeds should begin to crack open, and a tiny white root (taproot) will emerge.
• Some seeds may take up to a week, so be patient.

6. Transfer to Growing Medium
• Once the taproot is 0.25–0.5 inches (6–12 mm) long, carefully transfer the seed to soil, coco coir, or another growing medium.
• Place the seed about 0.5–1 inch (1.5–2.5 cm) deep with the taproot facing down. Cover gently with soil and water lightly.

Tips for Success
1. Use Fresh Seeds: Older seeds may take longer to germinate or fail altogether.
2. Maintain Humidity: Consistent moisture is key, but too much water can drown the seeds.
3. Handle Gently: The taproot is delicate and prone to damage. Use tweezers if needed.
4. Optimal Environment: Avoid cold or overly warm conditions, as they can inhibit germination.
5. Check Viability: Viable seeds are usually dark brown with a hard shell. Immature seeds (green/white) are less likely to sprout.


Once sprouted and planted, your seedlings will grow into healthy cannabis plants with the right care and environment!