Grow Op Farms operates a 90,000-square-foot plant canopy that includes nine greenhouses.
Photo by J. Craig Sweat Photography

As most cannabis cultivators will attest, managing a successful growing operation requires monitoring several variables and tracking each closely. The key is achieving a constant balance; even just a few degrees in temperature, too much water or too little of an essential nutrient can throw an otherwise healthy plant off course.

“Besides genetics and environment, there is no other greater controlling factor than nutrients,” says Mojave Morelli, director and head of cultivation for Washington-based Grow Op Farms, also known as Phat Panda. “Without regular additions of bioavailable macronutrients N-P-K, you are guaranteed to produce a less vigorous plant yielding far less mass than a plant that has a constant source of food.”

And yield is the most important metric to growers when selecting a nutrient line for their cannabis cultivation operation, according to data from the 2019 “State of the Cannabis Nutrients Market” study. Morelli says he’s seen yield increases of 5% with effective nutrient programs.

In addition to yield, Morelli says the correct balance of nutrients can result in increases in carbohydrates, electrolytes and resin production along with more powerful aromas and a boost in the amount of extractable oil.

Morelli manages Grow Op Farms’ 90,000-square-foot canopy, which includes nine greenhouses, 52 bloom rooms and 140 production strains. Tracking, testing and carefully recording this data is essential for a grower of any size but especially when working with a large facility with multiple genetics. Ensuring the plants have the food they need is priority No. 1.

Here, Morelli shares seven tips for managing a successful nutrient program, including how to sidestep factors that can derail cultivation operations and how to avoid the most common pitfalls even seasoned growers face.

1. Establish and maintain a clean environment for your cannabis crops.

In order for a nutrient program to succeed, cultivators and staff must start with standard operating procedures (SOPs) for proper grow-room hygiene. “The majority of sites we visit have deficits in grow-room sanitation,” Morelli says. These include staff wearing outside shoes and clothing in grow rooms and not properly washing their hands when entering and exiting the facility.

Keeping floors swept and free of debris is important, but light fixtures, fans and HVAC systems also must be kept clean and dust free. “The biggest problems I see across the board are cultivators not building systems for killing harmful bacteria like E. coli, listeria, salmonella, bile-tolerant bacteria, yeast and molds. We also see a lot of air handling equipment and duct work that isn’t being cleaned, ever, nor deodorized.”

2. Choose your nutrient supplier carefully and do your homework.

Ask potential companies to provide information about purity, ingredient sourcing, manufacturing practices, shipping and storing practices, Morelli says. Make sure they are using only the highest quality inputs and providing consistent solutions.

“We do a lot of fertilizer trials at Phat Panda, and I can attest to the inconsistency of particular formulas being sold on the market. The last thing a cultivator should be doing is having to worry if they are giving their plants a complete dietary package,” he says.

If growers aren’t sure what an ingredient is, Morelli advises to ask the supplier and do background research. Also, investigate what grade of raw inputs are being used. “Try and find products that use the highest-grade pharmaceutical or equivalent materials,” he says.

3. Use a nutrient with a balanced ratio of inputs.

Morelli says though price is important, consider other factors, including ingredients, inputs and the company’s track record. “Don’t just go with a nutrient line because of the price point or [because the company offers] new-to-the-market products,” he says. “We see lots of reformulations after products are released onto the market. Stick with manufacturers who have experience and a proven track record of delivering high-quality inputs.”

4. Mix and apply nutrients and supplements correctly.

“I see a lot of growers brewing teas with bat guano and other manures incorrectly,” Morelli says. “These concoctions are watered into the soil and often sprayed on the plant itself. Once product is sprayed, it can be a hotbed for bad bacteria [such as those listed earlier.] These bacteria, which are harmful to humans, can persist from a vegetative stage through the end of flowering and even remaining after drying and curing.”

5. When problems arise, diagnose and simplify.

When cannabis shows signs of stress, it’s often something other than nutrients affecting crop performance, Morelli says. Many problems stem from imbalances in environmental conditions or improper irrigation. Check lighting, temperature, relative humidity, vapor pressure deficit and CO2 first before investigating a nutrient program, and keep detailed cultivation records.

“Never make too many [nutrient] changes cycle to cycle,” Morelli says. “The fewer number of variables you have to sort through, [the better] when diagnosing plant issues and getting your genetics dialed in. Preventing these issues requires a diligent eye in the garden. Constant contact with the plants will enable you to make quick, corrective decisions to lessen any stress points that can have lasting effects.”

In addition, new plants should be quarantined off-site for two weeks before being introduced into the growing operation.

6. Maintain a healthy root zone.

Unfortunately, it’s often difficult to discern whether plant pathology is a result of root zone failures or nutrient problems, Morelli says, so getting ahead of any problems is key. If the root zone fails, the plant stops functioning and will produce a “dismal crop of mediocre flower at best,” Morelli says.

“Inoculate and don’t over or under water. Use strain-specific microbes and bacteria, as these products often have higher [colony-forming units] than large complex biopacks.”

7. Don’t overcorrect for pH.

A proper pH balance is essential because it affects nutrient availability. Because growers know how crucial this factor is, Morelli says many overcorrect when they see any slight changes in levels. “One of the biggest mistakes [that] new and old growers alike [make] is chasing incoming pH and outgoing pH,” Morelli says. “We’ve found that we grow a much healthier, happier plant when we allow our nutrient solution to move a few points in either direction without correction over a 24-hour period. Reading runoff and adjusting according to the results is also problematic as it can be difficult to discern what the results actually mean.”

Plants can readjust their own pH if they aren’t getting the right balance of macro and micronutrients, he adds. Correcting the situation before plants have a chance to adapt can lead to problems, such as nutrient lockout.

Michelle Simakis is editor of sister magazines Cannabis Business Times and Cannabis Dispensary.