by Olivier on 28/05/2018 | Cultivation

Growing cannabis in greenhouses

greenhouses Growing cannabis in greenhouses is the way of the future! This is the only way to combine the benefits of both outdoor and indoor growing. Cultivation is safer, more reliable and simpler than in the open air. You also save a lot of energy, which is good for your wallet as well as the environment.


The media regularly reports on raids in the cannabis scene. These reports usually concern commercially run indoor plantations intercepted by the police. We can thank prohibition that when we think of cannabis today it is linked to suspicious warehouses and energy-guzzling lighting.

There is, however, not a single lamp in the world that can compete with the power of the sun. In just one hour, 430 trillion joules of solar energy hits the earth. Just to be clear: That is 430 with 18 zeroes behind it. In theory, that’s enough to meet global energy needs for a whole year.

A greenhouse makes use this natural sunlight, which is superior to any lamp in terms of light intensity and light spectrum. No wonder that greenhouses are booming – from California to Israel, growers are backing this sustainable form of cannabis cultivation.

No life without the greenhouse effect

The atmosphere consists primarily of oxygen, nitrogen and argon, which are also described as greenhouse gases. They act as the earth’s protective shield and ensure stable, life-supporting temperatures.

A greenhouse works in exactly the same way: Light enters through the glass window and is stored in the form of heat. The terms ‘hothouse’ and ‘glasshouse’ are also used as synonyms.

The benefits of a greenhouse

Indoor shot of a huge greenhouse with flowering cannabis plants. Along the centre of the greenhouse there is a walkway, at each end of which there are fans.

If you want to grow cannabis, you need one thing above anything else: light. Lots and lots of light. And what better to provide it than a greenhouse with a transparent roof? The greenhouse effect ensures stable temperatures.

Cannabis likes it warm, but not too hot. Ideally, the temperature in a greenhouse should be between 21 and 25 degrees Celsius. Because a greenhouse can heat up very quickly, a ventilation system with one or more fans is recommended. Additional lights and heaters can be installed at the same time.

The flexible microclimate of a greenhouse offers multiple benefits: It allows the grower to intervene in the cannabis lifecycle and, for example, extend the vegetation phase. Cannabis can be planted earlier and harvested later. Theoretically, several harvests per year are possible – a benefit that is typically associated with growing indoors. In contrast to a grow room, however, the energy costs remain low.

A greenhouse not only provides protection from wind and poor weather, but also from burglars, thieves and vermin.

The disadvantages of a greenhouse

Close-up of a rainy window-pane with raindrops running down it.

If you want to grow cannabis in a greenhouse, you need enough space and a suitable location available. Ideally you want somewhere facing south or west.

A simple greenhouse does not cost much, but if you want to exploit the benefits of a microclimate, generally you will need additional lights, heating and a suitable blackout system. If you also want all these functions to be automated, then the costs can soon reach the same level as indoor growing.

Unwanted odours can be a problem. Active carbon filters can provide a solution, combined with fans. But in contrast to indoor growing, their effect is limited.

Tips for growing cannabis in a greenhouse

Whether indoors, outdoors or in a greenhouse: high quality seeds are a must! They are the starting point of any successful cultivation.

In principle, you can grow any variety of cannabis in a greenhouse. Even late-flowering Sativas, which tend to become mouldy in cold, wet Europe, will thrive wonderfully. Protected from the wind and the rain, they have enough time to reach full bloom. Remember that some Sativa varieties grow very tall, so the greenhouse will need to provide enough space. If that is not available, then the more robust, bushier Indicas might be a better choice.

They are also easier to hide between other plants; tomatoes, for example, are perfect for this. Here is another tip for anyone who wants to keep their growing away from prying eyes: Use white shading paint. It will also protect the plants from excessive heat. More modern polycarbonate greenhouses are not transparent, in which case no whitewash is necessary.

Plants in pots need regular watering and feeding. If they are growing directly in the soil, then the cost of caring for them can be kept to a minimum. In either case, the soil needs to be replaced each year.

Hydroculture is also possible in greenhouses, but is really only suitable for experienced or commercial growers.

Greenhouses require regular cleaning, otherwise diseases and vermin may establish themselves here too.

Which greenhouse is best?

From home-assembly constructions to a fully-automated glass palace – there is a greenhouse to suit every budget. There are basically three different types:

  1. A greenhouse extension is attached to a house, garage or wall. It does not need much space, and can also be used as a conservatory if required. Because it is an extension to an existing building, the cost of the materials remains low.
  2. If you have enough space available, you could consider a free-standing greenhouse. It’s fairly easy to erect a suitable construction made from wood, plastic or metal strips, and then cover in a transparent material. Ready-to-go greenhouses are of course also available to buy. They are delivered in sections and usually consist of profiles made from wood or powder-coated metal.
  3. At the commercial level, there are connected greenhouses. Generally a separate space is created for each phase in the plant’s life. Automated systems ensure optimum watering and feeding.

From the shadows into the light

Prohibition drove cultivation indoors but more recently, cannabis has found its place in the sun. Even today, a large part of the cannabis consumed in Europe and North America comes from greenhouses.

Greenhouses represent the cheapest, most efficient and most environmentally friendly option for producing consistently high-quality cannabis. This benefits not only commercial operations, but cannabis patients and recreational users too. One thing seems certain: cannabis from greenhouses is the way of the future!

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Frederick Monaghan

All your pictures above are of `polytunnels` covered in plastic.
At horticultural college, they taught me that glass is better than plastic because the plastic cuts out some of the light spectrum.

30/05/2018

Grass Chief

A greenhouse is superior to grow cannabis because it is better than any lamp in terms of light intensity and light spectrum. It uses natural sunlight which is a renewable energy. A fabulous post with lots of incomparable ideas.

09/06/2018

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