How To Grow Cannabis In a Greenhouse (5 Simple Steps)

Have you ever thought of growing weed in a greenhouse?

Turns out, greenhouses are ideal for cultivating more than just flowers, herbs, and cacti. A lot of weed enthusiasts and cannabis connoisseurs prefer growing their plants in a greenhouse. According to them, this kind of setup has many benefits (and very few disadvantages).

In this article, we'll explore the many benefits of greenhouse cannabis cultivation. We'll then walk you through the steps of how to grow cannabis in greenhouses. 

What is a Greenhouse & How Does it Work?

A greenhouse is a structure made of a metal frame and glass panels. It makes an artificial growing climate so plants thrive even in cold weather. 

Greenhouses use the "greenhouse effect" to work. Light passes through the transparent glass and hits plants and surfaces inside. This light energy gets converted to heat.  

Darker surfaces absorb more heat. The greenhouse glass transmits light but traps heat inside. This warmth benefits the plants.

The enclosed space stays warmer than outside. Plants get the light they need while staying protected in a controlled microclimate. This allows plants to grow year-round despite harsh or cold exterior conditions.

Benefits of Growing Cannabis in a Greenhouse

Greenhouse cannabis growing is increasingly popular - and for good reason. It has several benefits that are hard to argue with, such as: 

Best of Both Worlds. Greenhouse cannabis cultivation combines the benefits of indoor and outdoor cultivation. After initial setup costs, it is also an inexpensive method since you utilize free sunlight like outdoor growing. But it also shelters plants like indoor facilities from pests and animals. 

Control. A greenhouse lets you control growth phases.  In northern regions, the added climate control is very useful compared to being exposed outdoors. You can also extend the season and manage growth cycles. You can limit light exposure to force earlier flowering compared to at nature's whim outside.

You can also lengthen the growth phase for bigger plants and yields. With multiple grow cycles, harvests are much more abundant. And since greenhouses retain heat, you can start planting crops earlier than if you were to plant them outside.

Adjustable Climate.  Heating and ventilation systems in the greenhouse allow for cultivation to continue even when it gets too cold or hot outdoors. You can also control airflow to prevent mold and diseases. Or use heaters to prevent cold damage during the early days.  Outdoors this is challenging, but greenhouses let you optimize temperature and humidity.

Budget-Friendly. Finally, greenhouse growing is far cheaper than indoor setups. You avoid the high costs of artificial lights, ventilation, and heating that indoor facilities require. For an inexpensive but controlled cannabis crop, a greenhouse is ideal. But it uses natural sunlight and avoids expensive artificial lights.

Now that you know the benefits of growing cannabis in a greenhouse, here's how you can get started.

Step #1: Setting Up Your Greenhouse

Before you can start planting in your greenhouse, you need to set it up first. There are two major concerns to consider when you do so. You need to choose the type of greenhouse that best suits your situation. You then need to consider the location and security of your greenhouse. 

Choose the Type of Greenhouse

Greenhouses come in many sizes and styles at a wide range of prices. Different types will suit different environments or fulfill different needs. When choosing a greenhouse, consider the size, materials, local climate, and budget.

For instance, a small polytunnel hoop house with plastic sheeting over a basic frame is inexpensive. But it can only fit 1-2 plants. A lean-to greenhouse attached to your home provides easy access and insulation while utilizing existing wall space. But it will cost a little more. And you need to be sure you have ample space outside.

A standalone greenhouse offers ample room for multiple cannabis plants. However, it will require more yard space and, of course, a bigger budget. 

If you live in an apartment, you can use a small greenhouse cabinet on a balcony for discreet single-plant grows. If you have kids or pets, hard polycarbonate plastic panels are safer than glass. 

Different kinds of greenhouse roofing also offer different advantages. They can be pitched, domed, geodesic, or even-span. The best choice will depend on the weather in your area. A steeper pitched roof allows rain and snow to run off easily, preventing debris accumulation. However, flat and curved roofs offer better light transmission and distribution to the cannabis plants below. 

Note Location & Security

A greenhouse lets you grow cannabis more securely than outdoor gardening since it's enclosed. But don't just stick it anywhere. Pick a sunny, level spot protected from wind. 

Make sure to have good drainage too - maybe put down some gravel or set it on a slope. 

If weed's illegal where you live, a greenhouse helps you stay inconspicuous. Paint the glass white or line it with reflective material so people can't see inside. 

If you're concerned about the aroma, grow fragrant plants like tomatoes next to the cannabis. An ozone generator can also significantly cut down on smells.

And for extra security, get a greenhouse with a lockable door. Even if it's in a private, fenced yard, this will give you peace of mind.

Step #2: Setting Up Your Lights

Proper greenhouse lighting is essential for healthy cannabis plants and productive yields.

If you don't have the funds for an extensive light setup, focus on maximizing natural sunlight. Find a place where your greenhouse can get the most sun then plan the rest of your lights accordingly.

You should have grow lights at the very least. These will supplement the natural sunlight and ensure your weed gets enough light from seed to harvest.

Alternatively, you can look into securing cheap LED lights. They're energy-efficient, long-lasting, and work wonders for cannabis. Full-spectrum LEDs provide light wavelengths ideal for cannabis growth and flowering.

Look into securing reflectors and adjustable chains or cables to raise the lights. This is important since you need to adjust the light source according to the plants' heights. Adjustable chains also allow for even lighting distribution across the entire canopy. 

Optional (But Highly Recommended):

• Blackout Curtains. These will help you control the photoperiod your plants receive. This can start and stop flowering at just the right time.
• Metal Halide or High-Pressure Sodium High-Intensity Discharge (HID) Lamps. These are excellent artificial lighting options for indoor and greenhouse growth. If you have the budget for them, consider investing in a few. Running HIDs for 12-18 hours a day can give your plants the light they need to thrive through all their growth phases.
• Portable HID or LED Lights. These provide supplemental or interlighting among lower branches that may not receive as much light penetration.
• Light Meter. Use this to monitor your greenhouse's daily light integral (DLI). Adjust your lighting setup as needed to optimize your plants' growth.
• Remember that proper lighting is a core element for filling your greenhouse with robust, high-quality cannabis plants.

Step #3: Installing Ventilation

Proper ventilation is vital for maintaining ideal growing conditions in your cannabis greenhouse. In the summer, having the right ventilation system means fresh CO2 can come in while extra heat and humidity stay out. In the winter, ventilation gets rid of extra moisture to stop mold in its tracks.

Here's your game plan:

1. Install roof vents, side vents, and exhaust fans. These will circulate air, regulate temperature, and keep humidity at an acceptable level.
2. Optional: for optimal ventilation, consider investing in automated vents. These will open and close based on room conditions.
3. A tight-sealing entrance is also important for greenhouse climate control. Choose a high-quality, weather-resistant door with durable seals. This will limit air exchange, maintaining optimal internal temperature and humidity levels.
4. Optional: Installing an entrance vestibule can further preserve your greenhouse environment. It can create an airlock that controls outside air whenever the door opens.

Step #4: Water, Temperature & Growing Apparatus

Before you start planting your cannabis seedlings, you should know how you're going to water and nurture them. Here's where watering systems, nutrients, monitoring setups, and various growing apparatus will come into play.

Monitoring Water & Nutrients

There are several options for watering greenhouse cannabis plants.

1. Hose or watering can. Cheap, simple, and has a low risk of waterlogging. However, overwatering is a more prominent threat when you're watering plants by hand.
2. Modern drip irrigation system with tubes or oscillating sprinklers. This system is highly efficient and provides wider coverage - especially for larger grows. It prevents overwatering but has an increased risk of waterlogging roots. 
3. Automated watering system. This is the most convenient but also the most expensive. If you have the budget to invest in one, we recommend a high-tech hydroponic setup that delivers water and nutrients on a schedule. It takes the guesswork out of watering by delivering the right amount of water at the right times.

Whatever system you choose, always test your water quality. Make sure its pH level stays at 5.5 - 6.5, which is the ideal pH level for cannabis.

If using drip irrigation, be sure to implement a good drainage system. Drip irrigation runs the risk of waterlogging roots, and waterlogged roots can lead to root rot.  Use containers with holes to avoid this. 

For nutrients, it's best to follow the recommended schedule provided on the package. Start with a quality base nutrient line formulated for cannabis. You can use organic nutrients derived from natural sources or synthetic mineral salts.

Both will work well for growing great cannabis. Organic is better for the soil but synthetic mineral salts won't need as much monitoring. Use whichever you feel suits your situation best.

Then use additives like bloom boosters in the flowering stage as per the manufacturer's instructions. Additives like integrated pest management (IPM) nutrients have microbes that organically prevent mold and pests. Other additives like mycorrhizae fungi and bacteria are beneficial and can help your cannabis plants thrive.

Monitoring Temperature

The internal temperature and humidity of the greenhouse can greatly affect the health of your cannabis plants. Always monitor the numbers to ensure they stay within the following recommended ranges:

• Daytime Temperature: 70°F - 85°F
• Nighttime Temperature: 60°F - 70°F
• Humidity (Vegetation Stage): 40%-60%
• Humidity (Flowering Stage): 40%-60% 

You can use stabilizers like heaters and air conditioners to maintain ideal levels. For instance, space heaters and gas furnaces can be used to raise the temperature. You can also use propane, hot water, or steam radiators during cooler days or nights.

Just make sure your ventilation system is up and running first! 

For hotter or more humid days, you can use exhaust fans, evaporative cooling pads, and AC units. Passive ventilation from the vents may suffice during mild days but don't be afraid to use humidifiers or dehumidifiers as needed.

Automated climate control systems are very useful for maintaining ideal temperatures, humidity, and CO2 levels within the greenhouse. But if you don't have the budget for this, manual and consistent monitoring will work just as well. 

Growing Implements & Apparatus

A cannabis greenhouse requires certain implements and apparatus to create an ideal growing environment. While you can get away with a basic setup of planter pots, growing lights, and a watering (plus drainage) system, investing in these extra accessories can vastly improve the quality of your yield.

Here are some items you might want to consider for your greenhouse.

• Cover the floor with a weed barrier, then top with gravel or pavers for drainage.
• Install raised beds with aluminum, steel, or wood frames to provide space for plants' roots.
• Cover the beds with UV-stabilized and IR-transmitting polyethylene, polycarbonate, or glass to allow beneficial light.
• Add benches and shelving to accommodate propagation areas and supplemental lighting. Make use of vertical space by installing shelving or hanging lights. This maximizes your growing capacity.
• Include storage for gardening tools and materials.

Step #5: Growing & Harvesting Greenhouse Cannabis

Finally, your greenhouse is ready. Let's walk through the different stages:

1. Planting Seedlings. For best growth, plant cannabis seedlings directly in the greenhouse soil so roots can spread freely and avoid transplant shock. However, planting in pots allows more control over watering and nutrients. Pots also make it easier to move plants if needed.
2. Waiting Time. Cannabis typically matures in 7-9 weeks. Monitor trichome color for peak ripeness.
3. Harvesting. Flush plants 2 weeks before harvest by watering with pH-adjusted water to remove salts and improve flavor.
4. Post-Harvest Cutting. Cut whole plants and hang to dry in a dark room around 60-70°F and 60% humidity for 7-14 days. Trim off large fan leaves then manicure dried buds by cutting stems and removing sugar leaves. You can also wet or dry trim. Wet trimming after cutting speeds drying but takes more effort. After drying, cure buds in jars for 6+ months to improve flavor. Burp jars daily to control humidity.
5. Drying. Drying racks or nets allow even drying and make rotating buds easy. Use dehumidifiers, humidifiers, and fans to control conditions. Proper harvesting techniques maximize cannabis quality and flavor.

Conclusion

Growing cannabis in a greenhouse allows home cultivators to produce substantial yields of high-quality buds. Follow these guidelines for lighting, nutrients, temperature, humidity, and harvesting to get the best results from a greenhouse cannabis garden.

However, remember that the quality of your weed seeds will also affect the quality of your harvest. Even if you have a fantastic greenhouse setup, your yield will still be mediocre if your seeds are unhealthy or underdeveloped. That's why it's important to buy weed seeds from reliable and reputable sources like WeedSeedExpress. At WeedSeedExpress, we make sure our seeds are healthy, fully developed, and created with love by expert breeders and cannabis enthusiasts.