The Definitive Guide to Why it’s Better to Grow in a Cannabis Greenhouse

When it comes to growing cannabis, time is money. Cannabis greenhouses exemplify the concept of time efficiency. With the ability to start the growing season early and harvest throughout the winter, cannabis greenhouse growers can stay in business year-round. In addition, greenhouse growers can grow bud of superior quality and potency, while eliminating a lot of the costs that indoor growers face.

As cannabis legalization continues to spread across the country, growers need to know how to maintain the edge on competition. Cannabis greenhouses offer what warehouses and outdoor growing cannot: total environmental control, increased energy and labor efficiency and in turn, maximized profits. Every grower, no matter their experience level, can optimize the efficiency and profitability of a cannabis greenhouse by integrating the proper lighting, light deprivation and automated climate control and because of this, every grower should be utilizing greenhouses.

Cannabis Greenhouse Lighting

Natural Lighting Saves Money

Greenhouses take the best parts of outdoor growing and combine it with the best parts of indoor growing. By allowing natural sunlight in through the roof, growers are able to give cannabis plants the light they need, while significantly reducing their annual utility bill. The more sunlight that is used, the less supplemental lighting that is needed. In states that get a lot of sunshine year-round, like Arizona, California and Florida, it’s feasible to turn four harvests a year without using any artificial lighting at all.


Lighting is the biggest and most expensive inefficiency when it comes to indoor cultivation. In a warehouse setting, growers must constantly use artificial lights to recreate the power of the sun. Electricity costs for indoor growers are estimated at up to $750 per pound. Since greenhouses require one fourth as many lightbulbs as indoor grows and don’t need to be run 12 to 18 hours per day, electricity costs come in much lower, at $350 per pound. Industry experts speculate that greenhouses save growers up to 90 percent in energy expenses when compared to indoor facilities.

In addition to being lighter on growers’ pockets, reduced energy use eases the strain on the nation’s energy grid. Thanks to the power of the sun, cannabis greenhouses need significantly less energy per pound of flower than indoor operations. As cannabis production becomes more common, it’s important that growers try to minimize their use of energy, so as not to add stress to an already stressed energy grid.

Light Deprivation is Vital to Success

Equally important as lighting is the ability to block light out quickly. The purpose of light deprivation is to control the light cycle. Rather than waiting an entire season for sunlight conditions to change, a light deprivation system empowers growers to simulate short days and long nights to trigger flowering. By shortening the timeline from planting to harvesting, growers have more time to perfect their growing methods.

An automated, engineered light deprivation system is one of the most important investments a serious cannabis producer can ever make. It offers precision photoperiod control, cuts down significantly on human labor and minimizes mistakes. Instead of painstakingly removing and adding blackout curtains, growers need only watch as an engineered system creates complete darkness in seconds and opens up precisely when sunlight is needed again. When designed and installed by industry professionals, an engineered light deprivation system ensures a healthy return on investment.

GrowSpan Light Deprivation Greenhouse

GrowSpan Blackout System

A non-engineered light deprivation system will usually not last as long as an engineered system. By dropping a one-size-fits-all system into a greenhouse, there is a high risk of curtains dragging against lights, or even totally blocking vents and fans. Repeated use of a non-engineered system is bound to result in wear and tear that will lead to future breakdowns. When professionals engineer a greenhouse, they also design the positioning and bracing of the light deprivation system, which results in far fewer light leaks than a drop-in system and improves longevity.

GrowSpan Greenhouse Specialist Will Kacheris explained, “This significantly increases the lifespan of the blackout system by eliminating wear spots and decreases install time by eliminating on site errors from the other made to fit systems.”

Supplemental Lights

When it comes to driving yield, lighting is critical. During the off-season when there’s not enough sunlight for the growing cycle, supplemental lights allow growers to increase the amount of growing cycles and harvesting opportunities each year. Harvesting cannabis throughout the winter, at a time when many outdoor growers are out of commission, gives growers a serious competitive advantage.

Growers can space lamps farther apart in greenhouses than in indoor grow rooms, since natural sunlight provides most of the needed light. As a rule of thumb, cannabis plants that are still growing need about 18 hours of light exposure followed by 6 hours of darkness. To trigger flowering, plants should receive 12 hours of light and 12 hours of darkness. 

The two most popular types of lighting for cannabis greenhouses are HPS (high pressure sodium) and LED (light emitting diode) fixtures. HPS fixtures provide orange and red spectrum light, which encourages budding and flowering in cannabis plants. HPS lights work best when paired with natural sunlight, which is what makes them so ideal for greenhouse production. The heat given off by HPS lights also greatly helps to maintain warm temperatures.

greenhouse lighting

Now more than ever, growers are taking advantage of the significant energy-savings provided by LED fixtures. Because the energy used by LED bulbs goes primarily to light rather than heat, they are incredibly efficient and can usually last for 50,000 hours or more. This helps growers cut down on HVAC costs all year-round. Furthermore, since LEDs give off so little heat, they can be placed close to plants without the risk of burning them.

Check out these marijuana greenhouses from GrowSpan

Climate Control in Cannabis Greenhouses

Extreme weather conditions can devastate outdoor cannabis plants overnight. In 2016, Oregon experienced heavy rains that ruined cannabis plants on many outdoor farms. Nearby cannabis greenhouses, however, didn’t suffer any negative consequences from the rainfall. In fact, greenhouse growers gained an advantage in the market that year, as the sudden supply shortage allowed them to boost prices. When cultivating in a greenhouse, the only climate growers have to concern themselves with is the one inside the greenhouse itself.   

One of the biggest advantages of growing cannabis in a greenhouse is the ability to automate practically everything. Smart greenhouse controls are used to automate heating, cooling, lighting, shade systems, fertigation, ventilation, irrigation and more. With a computer-based system like a smart controller, all functions can be put on a timer, enabling growers to create the perfect schedule.

With properly placed sensors that detect changes in humidity or temperature, a smart controller will trigger the appropriate equipment to stabilize environmental conditions. For instance, if the temperature drops too low, a smart controller will turn on the heating system and turn it off once the proper temperature is reached.

greenhouse environmental control

Compared to older, thermostatic systems, like humidistats and thermometers, smart technology can seem like a big expense. However, the startup cost is made up for through electrical and labor savings within the first year of operating. It’s best to have the company that is supplying the computer-based system do the installation, rather than a local electrician.

“Working with low voltage contactors is not in the usual electrician toolbelt, so errors can be made in the field,” Kacheris cautioned.

Automated computer system companies will usually send out a team of specialists to a greenhouse to wire low voltage components. This makes it easy for an electrician to run the hot lines in.

Kacheris elaborated, “Also, the install team can help program setpoints, alarms, and cloud-based operations on site with you to provide complete assurance.”

Since smart controllers are calibrated to work with smart phones and laptops, a grower can adjust the environmental conditions inside the greenhouse no matter where they are located. If power or equipment should fail, a smart controller can send a notification immediately, so growers can deal with it right away. Climate controls can also be customized to an individual grower’s requirements and adapt to changes in operational needs.

Kacheris added, “There is no better feeling for a grower than being able to confirm your greenhouse is running correctly during a storm or hot weather event from the comfort of your own house, with the newer cloud-based systems.”

Human error is unavoidable in every type of horticultural practice. One of the leading culprits of stress, disease and infestation in cannabis plants is the human error that occurs when workers manually adjust greenhouse conditions, like opening vents or turning on fans. Using environmental controls to create a consistently perfect climate reduces the risk of error, while also decreasing labor costs and driving bigger yields.

A Cannabis Greenhouse Offers the Ultimate Versatility

Expanding an indoor growing facility can be difficult, since surrounding buildings can limit an expansion project, but expanding a growing space is much easier with a greenhouse. The same material that was used to construct the first greenhouse can be used to build a second or third unit and each greenhouse can easily be joined together through gutter connection.   

Warehouses and other indoor settings have allowed growers to stay hidden from public view, but as more states legalize cannabis, more growers are opting for cost-savings rather than discretion. Not only is a well-equipped cannabis greenhouse the most efficient way to grow, there is also tremendous flexibility when it comes to cannabis greenhouse design.

Growers can decide whether they want to grow in pots or containers, in the ground, hydroponically or using a combination of techniques. Cannabis greenhouses come in virtually all shapes and size and can be interconnected and custom designed down to the most intricate details. And since it can be placed anywhere, a grower can have their greenhouse positioned for optimal weather conditions. Cannabis greenhouses are the best way to produce quality cannabis while minimizing operation costs, lessening environmental footprint and most importantly, hitting the lowest cost per gram possible.  

A cannabis greenhouse provides the best of the indoor and outdoor growing worlds. The ability to harness the power of sunlight, combined with the convenience of deploying blackout technology precisely when it’s needed, is invaluable. Furthermore, a cannabis greenhouse that is outfitted with the right environmental controls brings the frequency of human error down to a minimum. It is for these reasons that growers everywhere should seriously consider the return on investment that a cannabis greenhouse can provide their business.

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