Indoor cannabis grows are expensive operations. Given the real estate costs, massive energy bills, and significant staffing requirements, it’s crucial to find a way to increase profits. Maximizing your grow space is one way to do this and that could mean vertical growing—the practice of producing plants in vertically stacked layers or vertically inclined surfaces.
In the food sector, vertical growing companies like Plenty, Aerofarms, Gotham Greens, and many more, are revolutionizing agriculture. But in the cannabis industry, which practically invented sunless growing, there has been notably less activity.
This is partly because high-pressure sodium lights (HPS), one of the most common lights used to grow cannabis for decades, run so hot that plants have to be many feet away to stay unharmed.
But LEDs run at much lower temperatures, so you can install them inches from the plant canopy. Their decreasing price and increasing ability to equal or exceed HPS yields are making LEDs the standard, finally opening the door to vertical growing for cannabis.
“The main catalyst behind cannabis cultivation going vertical is the improved performance of LED lighting,” says Thomas Rogers, LED engineer of Exact Lux. “Cannabis growers are approaching us wanting the most powerful multi-tier or ‘vertical farm’ lighting systems possible.”
Two Types of Vertical Farming
Stacked vertical (left) and true vertical (right) cannabis grows with LEDs. (Sean Walling/Leafly)
The most common method of vertical farming is a stacked vertical setup—levels of plant racks with LED lights above each rack. Plants are topped and defoliated to keep them short and bud-heavy.
Growers even stack in the flower stage, despite plants being large and top-heavy.
With true vertical growing, plants grow out the side of a column, and water and nutrients drip down from the top—see these examples from ZipGrow and Tower Garden.
Within the column, a hybrid method combines nutrient film technique (NFT), where nutrient water is passed directly over the roots, and aeroponics, a soilless grow method where roots hang in the air.
Pros and Cons of Vertical Growing
So why don’t all cannabis operations grow vertically, especially in this competitive new industry? Here we’ll look at some of the benefits and drawbacks.
Environmental Conditions Get Complex
Maintaining optimum temperature, humidity, and air circulation is tough for all cannabis grows. But in vertical growing there is even more variability in macro and micro environmental conditions because there are more plants, making control more difficult.
Because of this atmospheric variability, Hugh Gaasch, engineer at STEM Cultivation, recommends sensors to detect data points like moisture changes. “Shockingly, the majority of commercial growers I’ve seen to date use a single temperature/humidity sensor to monitor a room, even large spaces, over 20,000 feet.”
In contrast, STEM Cultivation uses one temperature sensor per 100 cubic feet. STEM collects data on: temperature, humidity, air pressure, CO2 levels, lighting levels, lighting power (kW) and energy (kWh), system air circulation rates, localized air circulation, VOC (volatile organic compounds), and HVAC power and energy, to name a few.
Mike Zartarian, from Zartarian Engineering, builds circulation systems for vegetable and cannabis growers. To decrease chances of mold and fungi, he says: “I recommend systems that push air right in between the racks above the plants, usually with small ducts that take air from the edges of the room to the center of the racks.”
Expensive to Set Up and Maintain
Although vertical growing of any kind will increase yield by maximizing space, when you add up the increased energy usage from more artificial lighting, an upgraded climate control system, the extra infrastructure required (ladders, racks, sensors, and more), and paying high-skilled agro-technicians, it is very costly for many.
Zartarian says: “It’s by no means impossible, but the jury is very much out on whether it’s cost effective long-term. If veggie growers prove it to be a dominant technique, I would expect to see more experimentation on the cannabis side.”
As it is, licensed operators he works with are struggling to meet demand and prefer to stick to more traditional techniques they know will produce.
Vertically grown cannabis needs a lot of hands-on attention during the flowering cycle as compared to, say, vertical lettuce crops which are more set-and-forget. The height of a plant must be closely controlled, which requires grow technicians to get up on step stools or scaffolding to reach into the plant canopy. These high-tier tasks may not be OSHA-compliant.
Certain Cultivars Work Better Than Others
The most successful cultivars for vertical growing are short, have big buds, and fewer leaves, so less defoliation is necessary. But if you’re a confident defoliator, the diversity of cultivars you can grow will broaden.
Arthur Brownsey, cannabis cultivation consultant at Four Trees, thinks most strains can grow vertically. “If you have a tight production schedule, group like-cultivars together, and plan accordingly, there are no restrictions to what you can grow.”
Agro-engineer Aja Atwood of Trella sees value in vertical growing, but the limited cultivars it serves made her determined to find another option. “There is a wide variety of strains out there that prefer longer vegetation periods and have a taller growth structure. In order to diversify, you need to train or trellis those taller varieties to stay within the space.”
To allow for vertical growing with a diversity of strains, she and her partner Andres Chamorro invented a grow unit, TrellaGro LST, that trains plants to grow horizontally. Each unit is vertically stackable and equipped with LED lights that follow it as it grows sideways, allowing for taller strains and less energy use.
In these early days, vertical growing has yet to revolutionize the industry, and some operations, focused on supplying a high-demand market, are sticking with traditional growing methods.
However, most operations already know the price of cannabis will likely drop as competition grows. In that climate, the future of cannabis could move up, not out.