June 01, 2020 13 min read

By Alexa Peters

Whether you’re a newly-licensed commercial cultivator or you’ve been licensed for some time, of course you want to optimize your indoor cannabis yields and make a splash in your local cannabis scene. Unfortunately, growing cannabis is easier said than done.

Though some of the highest quality cannabis out there is grown indoors, growing high quality indoor cannabis is more complicated than sticking a seed in some soil, or buying a few clones, and watering them.

Indoor Cannabis Cultivation: a Game of Many Variables

The quality of indoor weed comes down to controlling and monitoring an array of variables that can influence the quality of your flower—in particular, lighting, humidity, temperature, irrigation, and nutrients.

Maintaining this delicate balance is a dance that Mojave Morelli, Director of Cultivation and Farming operations at Phat Panda farms in Washington, knows well.

For six years, he’s been cultivating indoor and outdoor cannabis with the brand and troubleshooting every bump along the way—from overheated plants to a Chocolate Tube Slime mold infestation.

“With cannabis, all your variables are so tightly woven together that if anything in the balance that’s out, it really affects the plant,” said Morelli. 

And, while many first-time growers will start controlling variables by feel or instinct, expert commercial growers lie Morelli swear by investing in quality metering tools.

“Since we’ve started implementing technology into our operation, it’s really highlighted the pitfalls of the grower trying to assess thing by visual cues or gut instinct,” said Morelli. “By using technology and the plant sciences, we’re able to better cultivate our plants to have a higher and more consistent yield.”

In this Entrepreneur’s Indoor Growing Guide, we’ll break down the different variables that impact the quality and consistency of your indoor cannabis yield and the best, most cost-efficient tools that can help you dial in every aspect of your indoor commercial grow so you can be on your way to becoming a leading cultivator in your local cannabis industry.

Growing space: your cannabis cultivation facility

Before choosing your grow space equipment, an indoor commercial grower needs to consider the size of their licensed facility in order to maximize yield and investment.

Unfortunately, yield can be drastically impacted by the equipment used and your expertise as a cultivator, so experts like Danny Murr-Sloat of Colorado’s AlpinStash, caution against going large-scale and getting a ton of plants, especially if this is your first go around.

After all, the smaller you start at the beginning of each harvest, the easier it will be to tend to the plants and the less costly it will be to maintain them.

“I recommend people start small and easy,” said Murr-Sloat.

Hence, it’s best to find a sweet spot somewhere in the middle, where the amount of plants you have is manageable based on the technology you’ve invested in, but your plants still offer enough variety and yield to get you established on the market. 

For instance, Grow Weed Easy says, “The short answer is that for one grow light, you should plan on growing 1-8 plants. If you grow more than 8 plants under a single grow light, chances are you’re hurting your yields by not giving each plant enough space to thrive.”

Once these considerations are taken into account, there are two main types of indoor grow spaces to look at—grow tents, or custom grow rooms.

While grow tents are widely available at gardening stores and online, they tend to be smaller and can be less practical for large-scale commercial applications. That said, custom grow rooms introduce more upfront costs you may not be ready to invest.

“We don’t use grow tents at Panda but I have used them in the past. [They’re] definitely not essential but a great way to get started as building a room out can be expensive for someone just starting out and not sure if they want to invest a lot of money,” said Morelli.

Taking Morelli’s advice, a new cultivator business should consider using indoor grow tents to start and then upgrade to a custom grow room as your harvest and profits grow. Some of the most highly-recommended grow tents includeGorilla Grow Tents, which is the #1 selling grow tent worldwide, and one of the most highly-reviewed, according to their website.

Gorilla Grow Tents come in a variety of sizes from as small as 2 feet by 2.5 feet to as large as 10 feet by 6 feet, and are designed to support all the equipment you need for a great indoor grow. 

On the other hand, if you feel ready to create your own custom grow room, make sure it is large enough for the number of plants in your harvest, is airtight, light proof, and able to be built out to support the equipment you will need like grow lights, fans or heaters, and other climate control systems that keep the grow room conditions perfect for cannabis.

Indoor Cannabis Grow Medium

Cannabis plants can be grown indoors both in substrates like soil or peat and hydroponically, which involves growing a plant without soil in a water and mineral-rich solution.

There are pros and cons to both methods, and in the end, it comes down to the quality of the weed you’re looking to produce, how quickly you want to harvest, and the amount you want to invest upfront. 

Cannabis grown hydroponically indoors tends to grow faster and yield more, but if not tended to diligently, these plants are more likely to be lower quality and less terpene-rich, according to experts. Cost is another significant disadvantage of growing with hydroponics. 

“The initial cost to set up a hydroponic system is higher than the cost to set up a comparable soil-growing operation, and the operation of a hydroponic system is labor-intensive. So, ongoing costs for a hydroponic system are relatively high, too,” according to an article in SF Gate.

Morelli’s favorite way to grow is Coco Coir, a substrate made from ground up coconut pith and core. (Fox Farm’s Coco Loco potting mix comes highly recommended by multiple cannabis-specific growing sites.)

“We are a coco grower—it has a certain level of forgiveness that other hydroponic medias don’t provide. If you go too dry, other substrates won’t wet back up the same way,” said Morelli.

“Coco Coir is [renewable]. Peat, on the other hand, is a diminishing reserve. We try not to use it because the consumption of peat has been exponential in the last decade, and the quality of peat has gone down substantially. You can get an excessive amount of dampening off, and other issues.”

At the same time, you can grow great cannabis in plain old soil too, and in some cases, it’s the better option.

With soil, the grower can spend less upfront and have much more control over each individual plant, especially if each plant has its own container. According to Growberato.net, “This allows you [to] give each one its own treatment, allowing you to get rid of ill plants or problematic plants without affecting the rest.”

There are a variety of soils out there that cannabis can grow in—it’s a “weed,” after all—but the plants do best in soil mixtures that tend to have a loose texture and appear dark and rich, according to Grow Weed Easy.

One highly-recommended soil mixture for commercial cannabis endeavors is Miller Soils Red's Premium Biochar Blend.

Indoor Cannabis Grow Lighting

Next, lighting is one of the most important things when growing indoor cannabis plants.

Generally, the more light you can give your plants, the bigger and better your plants’ yield. But when you don’t have the sun to harness, that light has to be artificially created.

This is where grow lights come in, and where, yet again, you need to choose what route will be best for the size and objective your operation.

There are 3 main classes of grow lights you can use in cannabis—Fluorescent lights, High-intensity discharge (HID) lights, and LED lights. HID and LED are the most commonly used, and both options offer pros and cons.

HID grow lights include Metal Halide (MH), and High Pressure Sodium (HPS) lights. According toRoyal Queen Seeds, most advanced growers use a combination of MH and HPS lights throughout the duration of their grow.

MH lights, which elicit a cool, blue-tinged light, are most commonly used for vegetative plants, while HPS, with light on the red end of the spectrum, are best for the flowering stage. 

600W HPS lights are a very common choice throughout the industry, largely because they are less costly than LEDs. At the same time, HPS bulbs get very hot and degrade over time.

This means their radiant heat must be mitigated with a cooling system, and bulbs must be replaced periodically. Though this is the method Phat Panda uses, Morelli says there is a lot to weigh when choosing between HVS and LED.

Unfortunately, LEDs cost more upfront than a HVS fixture.

According to a study done in Weedist, LEDs run anywhere between $500-$1500, while a 600W HIDfixture will cost between $300 and $600 each year, depending on size. But, the study also showed that those initial costs were offset by the energy savings over time. 

“I used to tell people that LED grow lights were for those that could afford them, but looking at the data I see that it’s much cheaper to shell out for a nice LED than it is to run an HID for a long period of time,” wrote the author.

With that in mind, Morelli says that LEDs, like this fixture from Black Dog LED, might be the better option for a new company, especially when considering your energy bill.

“HVS bulbs create a lot of heat, and that can be a good thing because you need heat load in your room to some degree. Phat Panda maintains the right temperature by cooling,” said Morelli. “But, if you go with LED, they don’t produce heat. You need to introduce some other form of heat to the room. At the end of the day, I’d go with LED because cooling is often more expensive than heating.”

If you’re still looking to try out HPS lights, Grower’s Choice offers some of the bestHPS andMH bulbs and fixtures out there.

Additionally, thisresource offers several top-rated HVS fixtures that offer a lot of bang for your buck. For those of you seeking LEDs, Production Grower made thisgreat table, which weighs the drawbacks and benefits of 10 of the most popular LED grow lights in 2020.

Temperature and Humidity: What You Need to Know for Indoor Growing

The temperature and moisture content of your indoor grow-op environment is important, too.

This is where Morelli says spending an extra buck on heating or cooling systems, as well as environmental metering equipment, like thermometers and hygrometers, is essential.

“Temperature and humidity are big issues for most growers — getting them dialed in,” said Morelli.

“One of the biggest things we see is low humidity with high light. What happens is because there’s so much radiant heat from the lights, and if the cooling system isn’t dialed in, all the light rings out the water in the air. As the humidity goes down, the plant is trying to transpire (cool itself) more because it’s being overloaded and...the leaf will end up with a burn on it.”

Burnt, curled leaves are just one of the side effects of poor temperature and humidity management, which can also create a white powdery mildew on cannabis leaves, cause bud mold or rot, created nutrient deficiencies, and slow the overall growth of your plants.

Temperature and humidity can be monitored jointly by measuring Vapor Pressure Deficit (VPD), a measurement which rolls air temperature, leaf temperature, and relative humidity into on an easy-to-manage number. 

In order to calculate VPD, you need to measure temperature with a thermometer and pressure with a hygrometer and then reference a VPD chart to figure out what you may need to tweak to get the balance right. (For the vegetative stage, a VPD range of 0.8–1.1 (kPa) is ideal, while a VPD range of 1.0–1.5 (kPa) is ideal in the flowering stage, according toCannabis Science Tech.)

When looking to control temperature and humidity individually, there are a couple rules of thumb touted by experts like Robby Flannery of Dr. Robb Farms that can help you keep your operations on the right track.

“For temperature, let’s talk about the plants we have in flower that are actively growing—you want to have the temperature for those plants to be around 78 degrees,” he said. “When it comes to humidity, this is a crop that is unfortunately rather susceptible to fungal infection—so you want to keep the humidity relatively low, around 50%.”

Irrigation: Cannabis Needs Water

Like with any plant, cannabis needs water. But, as for how much and how often and in what way—watering cannabis can be a bit mystifying. 

Understandably, many growers tend to either overwater or underwater their plants, so it’s important to know certain visual cues that signify if a plant needs water—especially if you’re hand watering.

These major cues, according toLeafly, include if your leaves look yellow or droopy, and/or if the soil feels dry. 

From there, there are multiple ways to go about watering your plants.

Some growers swear by hand watering because it’s cheap and allows the gardener to attend to each individual plant’s needs.

That said, hand-watering hundreds, maybe thousands, of plants in a large-scale commercial operation just doesn’t make a ton of sense.

Not to mention, it can be incredibly imprecise—after all, the size of your containers, type of growing medium, temperature and light intensity, as well as your plant’s stage of growth all impact the watering process.

In this way, automated irrigation is a really great option.

Automated irrigation works by connecting individual plants to a water reservoir through a series of small tubes, droppers, or buckets. With a timer, you can control when and how much water is released from the reservoir, which the grower can program depending on the size of the grow containers, and whether the plants are in soil, coco coir, or hydroponic grow medium.

“Automating irrigation improves productivity and plant quality by making irrigation more uniform [and reducing] the amount of time your team must spend hand-watering the crops, creating more opportunities for staff training and development,” reports the Cannabis Business Times.

One common example of this sort of automated irrigation is an automated drip irrigation system, which can be easily modified to service a small indoor/outdoor garden or a large indoor/outdoor commercial operation.

What’s more, drip irrigation also uses less water than conventional hand-watering, and is more precise, too, preventing over and under-watering. (Royal Queen Seeds gives tips on how to make and install your own drip irrigation system, but if that seems too complicated, DripWorks is one of the longest-running drip irrigation manufacturers servicing the cannabis industry.)

Additionally, if you work exclusively in hydroponics, SuperCloset’s Bubble Bucket grow systems combines the technology of bubble buckets and ebb and flow buckets, and is another popular fully-automated hydroponic grow system.

Beyond how you choose to water, it’s also important to keep in mind that the pH levels of your water can affect your plants. According to several sources, the pH of your irrigation water should fall between 6.0 and 6.8. Water pH can be easily tested with pH sticks or measuring drops, and you can also buy “pH up” or “pH down” drops to adjust your water pH, if need be.

Cannabis Nutrients: Feeding Your Plants

Most cannabis plants often need more than just water to survive, particularly if they’re being grown hydroponically, without the soil that usually provides much-needed nutrients.

In this case, amendments that can provide supplemental macronutrients like nitrogen, phosphorous, potassium—also known as “NPK”—are a vital addition to your plants’ diets.

“Depending on the type of medium that people use, there are some soil mediums that will come with some nutrients baked in, and [the container] will say you don’t have to use nutrients for the first four or five weeks,” said Bryan Wolf, Marketing Specialist at Lotus Nutrients. “But essentially, with any medium you’re growing in, you’re going to need nutrients along the road.”

Choosing the right nutrients for your indoor plants is imperative, and based on several factors including the growth phase of your plants and how you’re growing your plants.

“The plants will need different nutrients at different times. During the vegetative process, when all its doing is growing taller, it will need different nutrients then when its flowering or getting ready to harvest,” said Wolf.

For this reason, Lotus provides a “Starter Kit” of nutrients designed to help with each stage of the plants growth, and many other companies provide nutrient blends for each stage, as well.

Next, if you are growing in good, rich soil, you can expect to use less nutrients than if you are a hydroponic grower because good soil already contains much of what the plant needs.

That said, there are soil nutrients, as well as hydroponic nutrients that can be adjusted to suit soil growing, too. For instance, though their nutrients are designed with hydroponic growers in mind, Wolf say Lotus’ products can be modified to suit other grow mediums. 

“Our feeding schedule is targeted for people who are growing hydro, but what we tell people who are growing in soil is use about 75% of what we recommend and feed every other time you water,” said Wolf. 

Lotus specializes in powdered nutrients that you mix and dilute yourself based on your particular needs.

Because of their adaptability, Wolf says powdered nutrients are a growing trend in the cannabis nutrient industry, even though powdered nutrient costs more upfront than pre-mixed liquid nutrients.

In fact, on their website, Lotus provides a great nutrient Feeding Schedule with guidance on how much of their nutrients to give your plants based on their growth stage. 

As for how to apply nutrients to your plants, Wolf says their commercial customers typically add their nutrients to the water reservoirs connected to their irrigation systems. 

“While, generally, a home grower mixes in a gallon to five gallons at a time into a big Home Depot jug— what commercial [growers] will do is they will scale up to a 50-gallon drum [based on our feeding schedule].”

Lastly, it’s important to keep in mind is that there are numerous other cannabis nutrient brands out there, each with their own proprietary nutrient blends and products. Because one product can be vastly different than another, follow the instructions specific to your product for best results.

Keeping Everything in Balance with Systems and Automation 

Clearly, cultivating cannabis is a lot like juggling—you’ve got several balls in the air at any given time, and if you drop one, the rest fall to the ground, too. Plus, commercial cultivation Is about more than just growing some flower—it has to be worth spending money on. 

And, as important as it is to understand how lighting, temperature, humidity, nutrients and other variables affect the indoor cannabis growing process, the best way to keep all those balls in the air—and maintain a consistent quality for your flower—is to automate as much of the growing process as you can.

As Candid Chronicle reports, “Businesses who invest in automated systems for lighting, feeding and data collection attest to their efficiency and cost-effectiveness accompanied by the reduction in labor costs and human error.”

If tight on funds, you can slowly add more automations to your operation over time, or hire companies like Climate Control Systems, who’ve built out automated grow operations for the medical cannabis industry for over 30 years, to build your facility out all at once. 

From there, growing great indoor cannabis—every time—will be far simpler, creating more time for you to connect with dispensaries, breed new strains, and further establish yourself as one of the best growers in your area.


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