How Cannabis Growth Stages Impact Energy Use and Lighting Needs

In this interview, Adam Jacques, owner of AgSense, LLC, and Zacarariah Hildenbrand, PhD, partner of Medusa Analytical, LLC both discuss the lighting changes that occur during the growing stages of cannabis.

Jacques explains the seedling, vegetative, and flowering stages, noting that vegetative plants often require up to 18 hours of light per day to maintain growth. Hildenbrand expands on how lighting intensity increases during flowering—from 400 watts in vegetative stages to as much as 1000 watts—to support trichome, cannabinoid, and terpene production in the flowering phase. He also notes the effect on cost of production.

Read more in our feature article, Engineering Efficiency: Optimizing Energy Systems in Indoor Cannabis Cultivation Facilities.

Transcript:

Erin McEvoy: Are there parts of the growth stage that require greater energy consumption from a lighting perspective?

Adam Jacques: So what you're looking at is two distinctly different phases in cannabis growth when you're growing inside. Well, three kind of. You're looking at, like a seedling phase or a clone phase, a baby phase, into a vegetation phase. Your vegetation phase where you're going to put the plant mass on to get it to the size you want before you put it into your bloom space. Unless we're talking about auto flowering, which we are not, most plants will maintain a vegetative state at 16 plus hours. For safety, we keep it about 18 plus hours. Some plants actually do require a 24 hour lighting cycle to not go into flower. Those we generally take out of the grows, because genetically, it just doesn't work for us. But 18 hours a day on vegetative plants, and I do like to keep the spectrum the same as I'm using in my room, so there's no transplant shock. So what you're seeing during that time is a usage of six more hours a day on the LEDs during vegetation. Vegetation, from clone to planting is about six weeks. So during that, that whole grow cycle, about six weeks of those are spent with that extra lighting.

Zac Hildenbrand: That's a great question. I mean, so the plants, again, they're doing two different things. Early on, they're putting on vegetative matter, and then in the second half with flowering, so you have a whole range of kind of chemical and hormonal changes. To really answer that question, you'd have to understand how much food they're consuming in the different phases, and that's ultimately a function of how much light you're giving them as well. So if you're going to hammer them, for example, let's say you were in veg, normally, we would hit the plants with 400 watts of full spectrum LEDs, about 24 to 36 inches off the canopy. And if we were to then go into flower now we're going to use more energy. So I guess I am answering your question here. Now we're going to go to 600 watts throughout, I'd say, 80% of the flowering cycle. And then maybe in the final two weeks, you raise it up to 1000 watts to really accentuate all of that flower production, phytochemical production, you know, you're talking trichome density, cannabinoids, you're talking terpenes, you're talking flavonoids. And so, yeah, the plants are going to eat a lot because they're getting more light. And so, yeah, I guess with as we talk through this, it's going to require a lot more energy in the second half of the cultivation cycle.

McEvoy: You could probably see that on your electricity bill when you're switching phases.

Hildenbrand: Yeah, and people are definitely watching that really, really closely. The unfortunate thing in the cannabis industry is it's very sinusoidal, up and down. For example, me and my partners got into the space where you could produce a pound of cannabis for $300 a pound, and you were selling it for $2,500 a pound. Great margin there. It allows people to expand and produce some interesting products and take their time. Now we fast forward to today. We've reduced our cost to produce, but still we're only getting $400 or $500 a pound. Is really, really thin margins and you have to have a really sharp pencil, so absolutely have to be following that electricity bill, because it goes into your cost of goods.