The benefits and challenges of a  cannabis greenhouse

Growing cannabis in a greenhouse can boost your yield and quality

But without the proper knowledge, you risk wasting time and money. This post offers solutions to optimise your greenhouse grow, helping you avoid common pitfalls like pest infestations and poor environmental control. 

We’ll explore the pros and cons of greenhouse growing, compare it to other methods, and provide practical tips to ensure your successful greenhouse cultivation. 

With our expert insights, you’ll be well-equipped to cultivate healthy, high-quality cannabis plants.

Disclaimer: Any information given on this site is for educational purposes only. Please ensure if you’re growing cannabis, you’re doing so by the law and subject to appropriate permissions and licenses of the applicable country.
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What is a cannabis greenhouse? 

A cannabis greenhouse is a structure designed to cultivate cannabis plants using both natural sunlight and partially controlled environmental conditions. 

Unlike traditional outdoor growing, a greenhouse provides a semi-controlled environment, allowing you to extend your growing season and protect your plants from harsh weather. 

Whether you're an experienced grower or just starting out, growing cannabis in a greenhouse could be the perfect solution for achieving high-quality cannabis crops.

Both feminized seeds and autoflowers can be successfully grown in a greenhouse.

Benefits of using greenhouses for cannabis growers 

Semi-controlled environment

One of the main advantages of a greenhouse cannabis grow is the ability to create a semi-controlled environment. 

You can install heating, dehumidifiers, and even CO2 enrichment systems to optimise your cannabis growing conditions.   

This level of control can significantly improve the yield of your cannabis plants and result in top-

 quality crops.  

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Extended growing season

Cannabis greenhouse growers can plant earlier in the season and grow strains that might not thrive outdoors. 

This particularly benefits sativa strains, which typically require a longer growing season. 

By using a greenhouse to grow cannabis, you can enjoy multiple harvests per year, maximising your production potential.

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Weather protection

A greenhouse protects your plants from adverse weather conditions. Rain and high humidity can lead to bud rot and other issues, but when you grow cannabis in a greenhouse, you have a barrier against these elements. 

This protection ensures your plants remain healthy and productive throughout their growing cycle.

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Flexibility in growing techniques

The structure of a greenhouse allows for various growing techniques. You can tie plants for support, remove glass panels or windows for better airflow, and attach grow lights when necessary. 

On sunny days, you can rely on your greenhouse plants enjoying sunlight; on cloudy days, you can supplement with artificial light. 

Blackout nets and light deprivation can also be used to flip from the vegetative stage and force flowering, giving you greater control over your cultivation process. This is how many  commercial cannabis greenhouses operate.

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Efficient use of natural light

Greenhouses make the most of natural sunlight, which is essential for robust cannabis plant growth.

The sun's light spectrum is more powerful than artificial lighting alone, leading to healthier and more vigorous plants. 

On days when direct sunlight isn't sufficient, you can provide supplemental lighting to ensure your plants receive the necessary light levels.   

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Challenges faced by greenhouse growers 

Initial investment and costs 

Setting up for growing cannabis in a greenhouse can be a significant investment. 

While the long-term benefits of bumper cannabis crops often outweigh the costs, the initial outlay for construction, heating, and other systems can be high. 

However, once established, the operational costs can be lower than indoor growing due to reduced heating and lighting needs.

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Visibility and security concerns

Greenhouses are not the most discreet option for growing cannabis. Their transparent nature can attract unwanted attention, which may be a concern depending on your location. 

Ensuring the security of your greenhouse is essential to protect your plants and investment.

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Pest and bug control

Greenhouses are more susceptible to pests and bugs than an indoor grow room. 

While the controlled environment helps, the proximity to the outdoor environment means you must be vigilant about pest management when growing cannabis. 

Regular monitoring and integrated pest management strategies are crucial to keep your plants healthy.

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Environmental control challenges

While growing cannabis in greenhouses offers more scope for climate control than growing outside, they are still subject to environmental fluctuations.  

Greenhouse temperature and humidity can vary significantly, especially with seasonal changes. 

Managing these fluctuations requires careful monitoring and adjustments with heating and cooling systems to maintain optimal growing conditions for cannabis production.

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Winter growing difficulties

Greenhouses can be challenging to manage during the winter months. Without proper heating and insulation, maintaining the necessary temperatures for cannabis growth can be difficult. 

Investing in a robust heating system and ensuring your greenhouse is well-insulated will help mitigate these issues allowing you to grow plants later into the season.

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Maintenance and upkeep

Keeping your greenhouse in top condition requires regular maintenance. Cleaning the glass to ensure maximum light penetration is an ongoing task. 

Automated systems, such as window openers and shade nets, can help but also add to maintenance requirements.

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Comparison with other growing methods

Greenhouse vs growing outdoors

The choice between greenhouse and growing outdoors largely depends on your local climate. In hot, dry regions, outdoor growing can yield excellent results. 

However, in cooler, more humid climates like the UK, a greenhouse provides the necessary control to improve yield and quality as your plants grow.  

A greenhouse grow protects against unpredictable weather, insects and poor soil quality whilst extending the growing season.

This offers a distinct advantage over traditional outdoor cultivation or growing in unsealed grow rooms. 

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Greenhouse vs indoor growing

Compared to indoor growing, greenhouses offer a balance between control and cost. 

While indoor grow rooms and growing space provide the highest level of environmental control, they are also the most expensive to set up and operate. 

Greenhouses, on the other hand, leverage natural sunlight and reduce the need for extensive artificial lighting and heating, resulting in lower operational costs.

Many people often prefer the quality of greenhouse-grown cannabis due to the natural light spectrum, leading to the most potent flower and flavourful buds. 

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What is the best greenhouse material for cannabis plants?

The best greenhouse material for cannabis plants depends on your budget, climate, and specific growing needs. 

Here are some popular materials used in cannabis greenhouses:

1. Glass:

Pros:

• Durability: Glass is long-lasting and can withstand harsh weather conditions.
• Light transmission: Provides excellent natural light penetration, essential for plant growth.
• Aesthetics: Offers a clear view and an attractive appearance.

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Cons:

• Cost: More expensive to install compared to other materials.
• Weight: Heavier, requiring a stronger structural frame.
• Insulation: Can lose heat quickly without proper insulation.

2. Polycarbonate:

Pros:

• Durability: Impact-resistant and can last for many years.
• Insulation: Provides better insulation than glass, helping to maintain stable temperatures.
• Light diffusion: Distributes light evenly, reducing the risk of hotspots.

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Cons:

• Cost: Mid-range cost, more affordable than glass but more expensive than polyethylene.
• Maintenance: Can become discoloured or scratched over time.

3. Polyethylene film / Polytunnels:

Pros: 

• Cost: This is the most affordable option, ideal for growers on a budget.
• Flexibility: Easy to install and replace.
• Insulation: Provides decent insulation, especially when using double layers with an air gap.

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Cons:

• Durability: Less durable, shorter lifespan. Typically lasting 1-4 years before needing replacement.
• Light transmission: Slightly lower light transmission compared to glass and polycarbonate.

4. Fibreglass:

Pros:

• Durability: Resistant to impacts and weather conditions.
• Light diffusion: Good light diffusion properties.
• Insulation: Provides good thermal insulation.

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Cons:

• Cost: It can be more expensive than polyethylene but less than glass.
• Maintenance: Regular cleaning is required to maintain light transmission, and it can yellow over time.

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TLDR

Polycarbonate is often recommended for the best results in a cannabis greenhouse due to its balance of durability, insulation, and light diffusion. 

However, glass is an excellent choice if aesthetics and maximum light transmission are priorities and budget allows. 

For cost-conscious growers, polyethylene film offers a practical and flexible solution.

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Commercial greenhouses

For a large-scale cannabis facility, a commercial greenhouse often offers the best balance between an indoor facility and outdoor growing.  

These structures are designed for high efficiency and can significantly reduce the costs associated with growing indoors. 

Using light deprivation techniques and greenhouse coverings, commercial growers can achieve multiple harvests per year and maximise their production capabilities. 

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Practical tips for greenhouse cannabis cultivation

Optimal placement

The location of your greenhouse is crucial. Ensure it receives ample sunlight throughout the day by placing it in a sunny spot. 

Avoid areas with excessive shade or where the structure might be obstructed by buildings or trees. 

Additionally, consider the local climate; being near a river, for example, might increase humidity levels, affecting your plants.

Consider how many plants you’ll be growing and whether you’ll raise more small plants or a few giant ones. Then, plan your greenhouse purchase and placement accordingly.

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Managing heat and humidity

Greenhouses can heat up quickly, especially in the summer. Paying close attention to heating and cooling needs is essential to prevent plant stress, promote healthy plants and maintain terpene levels. 

Shade nets, automatic window openers, and proper ventilation can help regulate temperature. Humidity control is equally important to prevent mould and mildew. 

Dehumidifiers and proper air circulation systems are vital components of a well-managed greenhouse environment.

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Automation and drip irrigation 

An automated watering system is highly recommended to ensure your plants receive consistent water, especially if you're growing in pots. 

Drip irrigation systems can provide precise and efficient water delivery, reducing the risk of over or under-watering. 

Automation helps maintain optimal moisture levels, promoting healthy plant growth.

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Seasonal adjustments

Adjust your cannabis growing practices according to the season. In the summer, focus on managing heat and providing sufficient shade. 

During colder months, ensure your greenhouse is well-insulated and equipped with heating systems to maintain the necessary temperatures. Be mindful of both electricity costs and energy consumption.  

Being proactive with these adjustments will help you maintain a stable and productive greenhouse growing environment year-round. 

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Takeaways

Growing cannabis in a greenhouse offers a unique blend of benefits and challenges. 

Greenhouses provide an excellent solution for many growers because they allow them to control the growing environment, extend the season, and protect their plants from adverse weather. 

However, the initial investment, maintenance, and environmental control challenges of a greenhouse require careful consideration and management.

Whether you're comparing it to outdoor or indoor growing, a greenhouse can provide the best of both worlds. 

By understanding the different types of greenhouses and implementing practical cultivation tips, you can optimise your greenhouse grow for maximum efficiency and yield. 

Happy growing!

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FAQs

Can you grow cannabis in a greenhouse in the winter?

Yes, you can grow cannabis in a greenhouse in the winter, but it requires careful planning and additional resources. 

The primary challenge is maintaining a stable, warm environment for your plants. You'll need a robust heating system to counteract the cold to achieve this. Insulating your greenhouse can help retain heat and reduce energy costs. 

Double-glazed windows or thermal screens are effective options. Additionally, using blackout curtains can help manage light cycles and retain warmth during the night.

Lighting is another critical factor. With shorter daylight hours in winter, supplemental lighting becomes essential. 

It’s critical to provide sufficient lighting to ensure your plants receive the necessary light spectrum for healthy growth. 

LED lights are a cost-effective and efficient choice; the next most popular choice is High Pressure Sodium (HID) grow lights. 

Humidity control is equally important, as winter air can be dry, which might stress your plants. Using humidifiers can help maintain optimal humidity levels.

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What’s the cannabis yield per plant in a greenhouse?

The cannabis yield per plant in a greenhouse can vary widely based on several factors, including the strain, growing conditions, and cultivation practices. 

Under optimal conditions, you can expect a yield of 350 - 700g  grams per plant. Factors influencing yield include:

1. Cannabis strain:

Different cannabis strains have different yield potentials. Some strains are naturally more productive than others. The most suitable strain for your greenhouse depends on your climate and the amount of space available. 

2. Growing conditions in your greenhouse:

Optimal light, temperature, humidity, and CO2 levels significantly impact the yield. Greenhouses allow for controlled conditions, which can enhance plant growth.

3. Cultivation practices:

Techniques like pruning, training, and ensuring proper nutrition can boost yields. Methods such as the Screen of Green (SCROG) or Sea of Green (SOG) can maximise space and light exposure.

4. Size and health of plants in your greenhouse:

Larger, healthier plants generally produce more buds. Ensuring your plants are free from pests and diseases will also help maximise yield from your greenhouse.

5. Grower experience:

Experienced growers tend to achieve higher yields due to their knowledge and expertise in managing the plants and the greenhouse environment.

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