Growing in the Greenhouse

Growing Greenhouse1The best structures and equipment for growing cannabis indoors

By Karli Petrovic

There’s more than one way to grow a plant. To grow a top-notch crop, however, it’s important to invest in the right structures and equipment for your production needs. Assessing those needs means considering three main factors — your climate, your budget and your production goals, prior to making a capital investment. Here’s what the experts had to say about selecting the right greenhouse and accessories for your operation.

Selecting a Structure

Some growers can successfully produce a crop in any structure or environment, but most greenhouse manufacturers agree that’s not the best approach for a cultivation facility.

“If you’re looking to grow a very high-quality product, strict environmental controls are necessary,” says Chris Guntermann, an Oregon sales representative for Horticultural Services. “There’s a big difference between 90% perfect and 100% perfect. Mold and bugs will downgrade the product, so high-grade products require high-grade controls. That’s also why it’s a good idea to talk with a greenhouse sales representative about your local climate and how much you’re going to grow. ”

Guntermann also warns growers to think about the operation as a whole and consider what type of equipment will be inside the greenhouse. “You don’t want to put $50,000 worth of equipment into a $2 per square foot structure,” he says. “That’s like putting a diamond in a plastic bag.”

When it comes to budget, the right structure can save growers from investing in additional environmental controls systems. This enables producers to grow more and earn more without spending more.

“The greenhouse is designed to efficiently provide the desired level of climate control and natural light transmission, thereby optimizing the plant production-to-cost ratio,” says FarmTek greenhouse specialist Zachary Carr. “The greenhouse must be designed appropriately if the grower is to attain his goal and maximize profits and cost savings.”

Carr says growers also need to weigh the pros and cons of the manufacturer, the sales representative’s knowledge and the quality of the greenhouse. “Is the manufacturer comfortable working with the cannabis industry?” he asks. “Spend your money with someone who knows what they’re doing and will be conducive to your profitability. Look at the manufacturers warranties and ask about metal quality.”

With respect to metals, Carr says it’s important to purchase a greenhouse with a galvanized steel frame because of its superior corrosion resistance and strength. He also recommends frames with galvanized steel tubing, instead of lower-cost options like c-channel and roll-formed framing.

The framing, though, is only part of the equation. Size matters, too.

“Most customers are using a 30-foot wide greenhouse so that they can get the required height,” the OBC Northwest team says. “When selecting a greenhouse, the pros and cons are about understanding greenhouse performance and what levels of performance will be acceptable to each individual grower.”

For optimal performance, Jonathan Valdman, president of Forever Flowering Greenhouses, advises customers to invest in a greenhouse with a ridge vent and roll-up side walls. This allows the grower to reap the benefits of passive cooling and avoid purchasing a costly cooling system.

“It’s similar to when your car becomes a hot box in the sun,” he says. “You roll down the windows and get the passive cooling. Lots of people use exhaust fans but end up pulling hot air in and pushing it back out. Another thing people try to do is introduce evaporative cooling systems or wet walls and close everything up. This introduces a lot more humidity, and when air moves from one side of the greenhouse to the other side, they end up getting inconsistencies in the crops. In this business, we want as much consistency as possible. That’s why we really focus on the passive cooling from this type of greenhouse.”

Choosing the Controls

As Valdman mentions, growers concerned with quality need to go beyond the greenhouse when outfitting their operations. Covers, shades, lights, and heating and cooling systems can increase a grower’s control over fickle Mother Nature. As with the structure, growers’ needs can vary wildly from one part of the country to another. One of the main things manufacturers suggest investing in is a first-rate greenhouse covering that won’t create hotspots in the growing environment.

“For coverings, we’re recommending high-diffusion glazing or ​canopies on the crop,” Guntermann says. “Most people are going with single or multiple glazes. Diffused options let in more light but bounce it around.”

Valdman adds that a cover should filter out harmful UVB rays, too. With the right covering, growers might not even need shade cloths to block out excess light. However, that advice doesn’t apply for places where the temperature rises well above 100 degrees. In those cases, Guntermann suggests using a cloth that will reduce the light level and cut the heat.

“We recommend not to use black shade​, which just makes the greenhouse hot,” he says. “There are reflective white or aluminized ​ cloths​ ​​that reduce the temperature, so the plants grow cool and bright instead of hot and dark.”

Like shade cloths, many equipment decisions are really business decisions. This is the case with supplemental lighting.

“Supplemental lighting allows day length to be extended during the short daylight periods of the growing season,” OBC Northwest says. “There are great grow lights on the market, but even the best do not produce the same spectrum of light as the sun. During long day length periods, the sun is the best light for photosynthesis. A grower’s best option is to harness the attributes of both supplemental and natural light.”

Guntermann adds that this can be an issue for growers who choose to produce cannabis year-round.

“During the winter months, you might get sunshine, but it will be low in the sky and go down early. This means your product will grow super slow. For comparison, tomatoes and cucumbers need extra light, and cannabis is nothing more than a fancy food crop. It’s not much different than broccoli.”

While a grower can always choose to invest in additional controls or automated systems, these decisions will be based on environmental, budgetary and production considerations. The best advice is simply not to try to make all these decisions alone.

“Greenhouse growing can be a rewarding opportunity but can be a bit imposing when it gets dissected into all the conditions that impact results,” the OBC Northwest team says. “A good saying is ‘plan your work and work your plan.’ Set parameters of expected results and put in place the necessary elements to achieve them. Refinements and changes are then introduced as conditions present themselves or require. Develop a support network of those that can provide results. Surround yourself with professionals, know your fellow growers and share experience freely.”


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