Grow Opportunity

10 misconceptions about greenhouses you should ignore

As the cannabis industry continues to gain legal status around the world more and more cannabis growers are learning about commercial-scale horticultural production techniques and, of course, that means greenhouse growing.

February 22, 2018  By Leigh Coulter

MYTH #6: One of the misconceptions of growing cannabis in a greenhouse is that you do not need heat because there are lights. Well As the cannabis industry continues to gain legal status around the world

Anxious to grab a piece of one of the hottest greenfield industries in decades, many consultants have jumped into the picture claiming to be manufacturers and greenhouse experts. Unfortunately, these groups are not always well informed and often perpetuate wrong thinking.

Here are the 10 most-frequent misconceptions we hear being told to cannabis growers looking to move to greenhouse growing.

1. You can’t grow in a greenhouse in the winter
If someone tells you this, walk away immediately and block their email, because they clearly have no understanding of the greenhouse industry. Tomatoes, peppers, roses, lilies, lettuce, among others, are grown in abundance throughout Canada, the northern United States, Europe and Japan year round. Niagrow Systems was established in 1978 with the sole purpose of providing top quality heating systems for greenhouse growers throughout North America, and thousands of greenhouse growers can attest that with a properly designed greenhouse heating system, quality plants can been grown year round.

2. You must heat a northern greenhouse year round
Only slightly less ridiculous than the first statement, this comment is an indication of little understanding for how greenhouse technology is adapted to different geographic needs. Often smaller companies who are more locally focused will make this kind of error. If the company you are working with is not from your geographic region then take this misstatement as a sign that they are not knowledgeable enough to give you proper greenhouse advice. Greenhouse heating design experts factor in the climactic region, the style and size of greenhouse, the specific needs of the crop, and the insulation factor of the greenhouse glazing material. Properly designed greenhouses are built to provide the ideal environment for your crop. If you consider how often your climate is below your desired cannabis crop temperature, you will quickly see what percentage of the year you will need to be able to heat the greenhouse.


3. You must provide year-round air-conditioning for southern greenhouses
A modification of the northern greenhouse misconception, these misinformed people are painting a large region with a single brush. Every project needs to be looked at individually because there is no one and only “cannabis greenhouse.” In Southern California, Mexico and Eastern Texas, for example, fan and pad systems work very well for greenhouse growers. In environments with higher humidity levels like Puerto Rico, for example, fan and pad systems are not effective. A greenhouse without a cooling system of some type will not be able to get below ambient temperature, so considering your climate will help you determine if additional cooling is needed, and if so how often.

4. Dutch greenhouses manufacturers understand cannabis growing best
In the Netherlands growing cannabis is illegal. With all the freedoms that Amsterdam offers cannabis consumers, growing the plant is not legal. On the other hand, medical marijuana has been legal in California since 1996 and in Canada since 2001. North American greenhouse manufacturers have considerably more experience with legal cannabis growing than manufacturers from other parts of the world.

5. There is a specific greenhouse design for cannabis
This one is popular with supply companies who are interested in fitting growers into a cookie-cutter model rather than working with the grower to find the best solution for them. Greenhouses have many different options, and growers should want to work with a greenhouse manufacturer that is interested in helping them grow. Different geographic regions and different licensing regulations require different growing techniques, systems and greenhouses.

6. I don’t need heat in a greenhouse because I have lights
There is a great deal of talk within the cannabis industry about the amount of heat that lights generate, and when you move from an indoor grow to a greenhouse you will still want to have lights. In a greenhouse, however, the lights are for supplemental purposes to give you a boost when natural daylight is not enough. So if you want to use your lights for heat, and you are growing cannabis, and you want light for only 12 hours a day while flowering, you still have 12 hours that potentially need heat but have no light. And since this 12-hour period is going to be at night, the temperatures outside the greenhouse will also be at lower temperatures.

7. High-tech greenhouses grow top-quality cannabis and mid-tech greenhouses grow mid-quality
While some greenhouse manufacturers and consultants would like to believe the entire success of a grower is due to the greenhouse structure and greenhouse equipment, this is just not the case. Top-quality growers will grow top-quality plants, and poor-quality growers will grow poor-quality plants. What the right greenhouse structure and the right greenhouse systems will do is make it easier for good growers to grow top-quality cannabis. Many of the systems, like environmental control computers, light deprivation screens, rolling benches, fertilizer injectors, etc. are more about production efficiency than specific plant quality. Plant quality generally goes up with proper use of high-tech greenhouse systems because the automation reduces human error variables. Often it is wiser to add technology in stages so you and your staff are able to fully understand the benefits of new greenhouse systems.

8. The capital investment in a greenhouse grow is more than what  is in a warehouse
When building a greenhouse, the capital investment is typically significantly less than a warehouse indoor grow. If you believe that growing cannabis in a greenhouse is the right approach for you, make sure you are building a relationship with a real greenhouse manufacturer, a company that can show you how to get the most value from your greenhouse build.

9. Light deprivation is brand new technology
Outside of the cannabis industry, light deprivation curtains are referred to as blackout curtains. This is common commercial greenhouse technology used for many plants that benefit from adjusted daylight hours; including poinsettias, kalanchoes and chrysanthemums. Vertical and horizontal curtains, light traps on fans and more help cannabis growers use economical commercial greenhouse technology to adjust the environment inside the cannabis greenhouse to the ideal plant environment.

10. You can expect an ROI of less than a year for a cannabis greenhouse
Fantastic returns on investments are often quoted by equipment suppliers and consultants to garner excitement and separate you from your money. Don’t believe anyone that is too quick to throw out ROI promises without taking the time to understand your business plan. There are a lot of people out there who think growing cannabis is easy money. Those of us who have been in the business for a while know this is far from the truth.

Leigh Coulter is the president of GGS Structures Inc. (, a greenhouse manufacturer with sales worldwide.

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