How to Grow Cannabis in a Greenhouse

What’s a midway between growing cannabis in a room or out in your garden? A greenhouse. 

Greenhouses offer terrific advantages, making them suitable for many growers who want to protect their plants from the elements, let them bask in natural light, and extend their growing season. 

A greenhouse is nothing but a transparent structure erected to protect delicate plants (read: cannabis) from the environment. It can also help you prevent various pests, diseases, and other common problems cannabis can face due to environmental factors. 

It is an excellent tool that has the potential to boost your plant’s growth and yield. It can also let you grow cannabis year-round without having to invest in extensive and expensive indoor growing equipment. 

Essentially, a greenhouse helps you create an ideal environment for your plant to grow while utilizing the natural sunlight and heat while keeping the adversaries out of reach.

If you've got some space outside along with experience growing cannabis plants, a greenhouse may be a great option. 

In this article, learn all about growing cannabis in a greenhouse.

Benefits of Using a Greenhouse for Cannabis

As mentioned above, a greenhouse offers various benefits that set it apart from other growing methods, like a garden or a grow tent. Let’s delve deeper into them below.

1. Longer Growing Season

If you grow cannabis outdoors, you have to rely on the seasons. In northern regions, where the summers are shorter, you only get a few months to grow your cannabis. Sometimes, that may not be enough.

In such cases, a greenhouse may be perfect for you. It can extend the growing season well into the fall and winter months. Plus, you can also begin cultivating before the winter is over with a greenhouse.

All you have to do is invest in a few modest grow lights to compensate for the lack of light during shorter or cloudier days, and perhaps a space heater to manage the temperature and humidity.

2. Ideal Conditions for the Best Growth

A greenhouse is generally warmer than the external environment, which is useful if you live in a colder region. Plus, it protects the plants from the harsh, chilly winds. 

Even if you don’t invest in a dedicated heating or cooling system, you can strike a consistent temperature within the greenhouse easily, thanks to its isolated microenvironment. 

Thanks to this benefit, your plants can enjoy the ideal conditions throughout their growth cycle and reach higher limits with bountiful yields.

3. Consistent Harvests

Speaking of bountiful yields, with a greenhouse, you don’t have to rely on external weather to yield big, bushy buds. A greenhouse’s controlled microenvironment allows the plants to grow high-quality buds consistently during every growing season.

4. Energy Efficiency

If you want similar results of an outdoor plant in your grow tent, you have to invest in high-powered grow lights, heaters, and humidifiers. A greenhouse eliminates the need for such investments while offering similar protection for your plant.

The result? You can grow high-quality cannabis plants safely without spending thousands of dollars on energy bills every year. Plus, this makes your growth more eco-friendly!

5. Protected, Discreet Plants

But if you are growing outdoors, you have to constantly worry about pests, mold, or diseases. A greenhouse eliminates most of this risk since it is an isolated microenvironment, which is a lot safer and healthier for your plants.

Additionally, cannabis has one more risk — thieves, vandals, or the government snooping into your garden. A greenhouse allows you to grow discreet outdoor plants without being prone to uninvited guests.

6. Inexpensive Solution

Lastly, a greenhouse is an inexpensive solution to growing plants safely. You need to make a basic investment in purchasing the greenhouse, but if you buy a high-quality one, it can last you for decades. Imagine the buds you can harvest during this time?

The initial cost of buying a greenhouse is well worth it. But if you want to save even more money, you can even build your own greenhouse. It may require a few days and some elbow grease, though.

Guide to Growing Cannabis in a Greenhouse

Growing cannabis in a greenhouse is fairly easy, so you don’t have to get too technical about it. Just keep the following steps to grow cannabis in your greenhouse.

1. Get Your Hands on a Greenhouse

Your first greenhouse does not have to be massive or expensive, it can simply be a small greenhouse. Just remember that whichever greenhouse you choose (or build) fits your needs, space, and budget. 

And purchasing a greenhouse is also easy. Tons of websites offer pre-build greenhouse kits or DIY kits, or you can pay a visit to your local gardening store. More on getting a greenhouse below.

2. Choose the Right Equipment

Once your greenhouse is ready, you then have to sort out the equipment. Depending on your local climate, strain, and some other factors, you may not need all of these. Still, here are some of the equipment you need to consider:

• Heating or cooling system

In some places, you may require artificial heating or cooling systems. If your greenhouse requires this to maintain optimal temperatures, the best way is to get a space heater or a cooler — garage heaters work like a charm. 

If you want to raise the temperatures, you can even start a compost pile in your greenhouse. You will be surprised at how much heat it radiates.

Then, you need to ensure that the temperature within your greenhouse is consistent and there are no hot spots. For this, you need to invest in fans to circulate the air throughout the greenhouse.

• Supplemental grow lights

During the beginning of grow season or the end of it, your local region may not have enough daylight hours to sustain the plant. The weather may also get cloudy or dull on some days due to the changing seasons.

In this case, you can either choose HPS or LED lights, but we recommend LED lights. LEDs are more energy-efficient, have an extremely long life cycle, and best of all, you can tune their color spectrum according to your plant’s growth stage.

• Ventilation

Apart from fans, you will also need a ventilation system, including basic ducts or windows, to allow the external, natural air to circulate within your greenhouse.

You should also consider applying a fine-screen covering on the vent openings to prevent the heat from escaping the greenhouse and contaminants and pests from entering within. 

3. Pick the Right Strain

One of the most important steps of growing cannabis in a greenhouse is choosing the right strain. Depending on your greenhouse size, it may be small for many cannabis strains. 

So, first, choose a strain that is suitable for your local climate, available space, and whether or not they require artificial grow lights.

Next, you need to choose the type of strain — between autoflowering and feminized photoperiod strains. Here’s more on them:

• Autoflowering strains

Autoflowering strains don’t rely on the light cycle to switch from the vegetative to the flowering stage. They are best for greenhouses using natural sunlight as they can handle mild variations in sun exposure without any problems.

Plus, you can harvest autoflowering plants grown in a greenhouse any time of the year. And they are suitable for small greenhouses, too, thanks to their stout stature.

If you are worried about the yields, you can try using the sea of green (SOG) method to grow autoflowering plants. Here, you compensate for lower yields by growing many autoflowering plants in close proximity. 

• Feminized photoperiod strains

On the other hand, feminized photoperiod strains are like regular strains that rely on the light cycle, but since they are feminized, they don’t grow into male plants in most cases.

They tend to fare well in regions with consistent daylight hours, but if you live in a region with short daylight hours or short summers, you may need to invest in grow lights to control their growth.

Do note that you will also have to light-proof your greenhouse during the night because even a small light leak during the dark hours can push your plants into re-vegging. 

Take care of your plant until it is ready to flower. Then, you can use blinds or covers to light-proof the plant during the night. You can either use blackout covers or blinds to prevent light pollution within your greenhouse. 

Some of these strains tend to grow tall and spindly in greenhouses, so you may also need to employ some training methods like topping or ScrOGing to control their size. 

Some of the best strains for greenhouse cultivation are:

• Critical Mass Auto
• White Widow Auto
• Jack Herer Auto
• Gorilla Glue
• Blue Dream 

Read the strain descriptions on the seed bank's website and avoid naturally long strains. Greenhouses have limited space, so tall strains don't make a lot of sense. 

4. Choose Your Growing Setup

Now, you have to figure out how you are going to grow your cannabis plant. You can grow your plants directly from the soil, use containers with soil and coco, or use a fancy hydroponic system. 

Soil, whether growing in pots or ground, is easy, especially in a greenhouse, since you get to control the entire ecosystem. And hydroponic setups give you even more precise control over the plant’s growth, but they require more time and effort to tune in. 

See what fits your preferences and choose that. 

5. Time Your Cultivation

If you are planning to use natural sunlight, timing your cultivation is something you must be careful about. You want to ensure your seedlings are ready to be transplanted into the greenhouse at the end of winter when the daylight hours start getting longer. 

You also need to ensure that your plant will be mature and ready for harvest before the next winter sets in. 

And even though your greenhouse will be slightly warmer than the outside environment, you should wait until there is no risk of frost. So, the ideal time to start growing cannabis in a greenhouse is during early or late spring, depending on your local weather.

If you are planning to use artificial lights to supplement the natural light, you don’t have to worry so much about timing. Just ensure your plant is not exposed to extreme weather and progressively use your grow lights to supplement the natural sunlight, as required. 

6. Always Germinate Indoors

Building on the previous point, you should always germinate your seeds indoors. This will not only offer your seeds a healthy environment to sprout in but also give them a head start. Your seedlings will be ready for the final transplant by the beginning of spring!

Germinating seeds indoors is quite easy. All you need is a few paper towels and low-powered CFL lights. And this does not take up a lot of space either.

7. Transplant the Seedlings Gradually

When the seedlings are ready for the final transplant, you should be careful and gradual with the process. If you transplant them directly into the greenhouse, they may experience shock, which is something you don’t want. 

Instead, once the seedlings are ready, move them into the greenhouse for a few hours for a week so that they can get used to the greenhouse environment. Gradually, increase the time they spend in the greenhouse. 

Doing so would reduce the stress on fragile seedlings and let them grow without any problem. 

Follow these steps and grow your cannabis plant as usual. That’s it. 

How to Choose a Greenhouse

A critical aspect of growing cannabis in a greenhouse is choosing the right type of greenhouse. Here are the most popular types of greenhouses:

• Pop-up greenhouse

A pop-up greenhouse is a simple, small greenhouse that you can “pop up” in your backyard. High-quality ones even come with a few shelves, a cover, and a bare frame so you can customize them as per your needs. 

• Polytunnel greenhouse

These greenhouses are shaped like a tunnel — hence the name — and they are easy to assemble and offer a lot of room to grow plants inside them.

• Lean-to greenhouse

If space is an issue in your garden, you can choose this. Lean-to greenhouses are slanted and hoisted against an existing structure, like a wall, and they can help you maximize your small garden space. 

There are many other forms of greenhouses, but they are more technical and sophisticated. For a new greenhouse grower, the above-listed ones are the best options.

Like most other things, you get what you pay for. So, avoid cheap greenhouses as they are flimsy, weak, and may have many leaks. Instead, always choose high-quality greenhouses. And if you are building your own greenhouse, stick to high-quality materials for reliability and long life.

Prebuilt vs DIY Greenhouses

You can either purchase a complete greenhouse kit that you can assemble easily in a few hours, or you can build a greenhouse from scratch. Both routes offer their own benefits, so choose the one that fits you best.

Prebuilt Greenhouses

Prebuild greenhouses are convenient and easy to set up — like an IKEA wardrobe — but they tend to be more expensive. You can purchase these in any shape and size you want, but remember to always buy from a reputed company.

Sure, the initial cost can be a bit high, but high-quality prebuilt greenhouses can last decades without breaking down or flying off due to the wind. 

DIY Greenhouses

On the other hand, you can make your own greenhouse easily. There are hundreds of tutorials on the internet that show you how to assemble a greenhouse of all shapes and sizes. 

But in this route, you will have to source high-quality materials like PVC or wood, greenhouse covering (polycarbonate, glass, or plastic), and figure out the shelves or frames within the greenhouse to hang fixtures.

You should also avoid any mistakes while sealing the greenhouse, as even minor leaks of air or light can cause major problems for your cannabis growth. 

Greenhouse Covering Type

Greenhouses come in various covering types, including fiberglass, glass, or plastic. They have their unique benefits, such as the following:

• Glass coverings are by far the best because they stay clear for a long time, are non-combustible, and transmit an excellent amount of radiation without turning yellow or brittle from sun damage. 
• On the other hand, fiberglass coverings are also a great choice for beginners. They are inexpensive, offer high levels of rigidity against the weather, and you can customize and cut them as per your preferences.
• Lastly, plastic coverings are also gaining a lot of popularity for their light diffusion and discreet look. However, they may not be the best option if you are trying to be more eco-friendly with your growth. 

Diffusion of Light

Some greenhouses also offer a light diffusion feature, where the covering is opaque, making the light diffuse instead of allowing direct sunlight within.

Diffused light has various benefits: it keeps the greenhouse cooler during hot summer days, prevents hot spots within the greenhouse, and makes your growth more discreet.

If your region gets too hot during summer or you want to prevent others from getting a peek into your greenhouse, you should consider a diffused or semi-diffused greenhouse.

Extra Tips for Growing Cannabis in a Greenhouse

Extra measures are always better when growing cannabis, especially in a greenhouse. So, to make your growth better, here are a few tips to help you out:

• Monitor the temperatures

Always keep your greenhouse temperatures in check since it may experience heat spikes during hot summer days. You should consider installing a simple thermometer in your greenhouse to keep an eye on the temperatures.

• Do not ignore the importance of fans

While fans are not mandatory in a greenhouse, we always recommend using them to keep the airflow fresh. In stagnant air, mold can be a big problem and the humidity may also increase.

A few fans strategically placed within the greenhouse will keep the air circulating, preventing the risk of mold or humid spots.

• Be mindful of space

Space is limited in a greenhouse, so always be careful. Start by reading the strain’s description carefully so you know what size to expect from your plant. Also, avoid lanky strains that can take up a lot of room, like pure Haze strains.

And if the plant gets too big, you can use training techniques to control its size. 

You can also just grow smaller plants and use SOG setup to get similar levels of yield as bigger plants. 

• Make your greenhouse more secure

A greenhouse is something many kids want to look at, but your greenhouse may also attract other kinds of unwanted attention. So, to protect your plants, choose opaque coverings so no one can get a look into your garden.

You can also install door locks, cameras, and burglary alarms to further secure your greenhouse from intruders.

• Keep the greenhouse clean

Dirt in your greenhouse can not only attract pests but can also fester mold and fungi. So, regularly clean out your greenhouse to remove any debris like fallen leaves to prevent many problems that would otherwise harm your plant. 

• Maximum sunlight, always

When setting up your greenhouse, ensure it is exposed to as much natural sunlight as possible. Since your plants need at least 12 hours of light to grow well, place your greenhouse in an open space with a lot of light exposure. 

Summary: How to Grow Cannabis in a Greenhouse

Using a greenhouse is an obvious choice for growing cannabis if you want terrific yield while minimizing your reliance on expensive equipment and protecting your plant. In the long run, if you use the greenhouse well, you can grow terrific plants with amazing buds. 

And yes, while the greenhouse may cost you some money, it is worth it. Over time, the benefits pay for it. 

If you are considering growing cannabis in a greenhouse, go ahead and start today. But if this is a new technique for you, don’t stop exploring this method and learning more about it.

Even the best equipment fails if the grower is not well-equipped with the right knowledge. So, keep expanding your horizons, and rest assured, that your greenhouse will not let you down.