5 Things Every Grower Should Know

Dialing-in your grow environment is essential to produce the highest quality cannabis. What does the environment have to do with flower quality? Cannabis produces over 500 chemical compounds in different ratios and proportions and it is the aggregate effect of those compounds that give a strain its “effect.” The chemical compounds potentially produced are determined by a strain’s DNA, but the environment impacts how much of each chemical compound is produced; sometimes even producing compounds that aren’t produced under sub-optimal conditions.

That means that once you’ve dialed in a strain’s environment to maximize its genetic potential, you will need to be able to recreate that environment so you can produce flower of that quality repeatedly, and with minimal variation from one harvest to the next. Below are a few concepts that hobbyist and commercial growers alike can focus on to optimize their growing environments:

Pressurized Grow Rooms: (Most growers opt for one of 4 styles of air environments.)

Positive pressure: This condition is created when you introduce greater volumes of air into your room than you exhaust. The pressure of the incoming air will force air out of the room through gaps in doors, windows, walls (outlet covers,) etc.
Pro: Better for pathogen exclusion; the pressurized air leaving the room will effectively create a barrier against entry.
Con: Difficult/costly to introduce CO2 & odors will escape.

Negative pressure: This condition is created when you exhaust more air than you introduce. The pressure gradient in this case will suck air in from gaps in doors, windows, walls (outlet covers) etc. Negative pressure is often seen when growers that use Carbon Filtration and Exhaust the air from the room without actively replacing it.
Pro: Better for odor remediation.
Con: Difficult/costly to introduce CO2 & can introduce past and pathogens via untreated air.

Sealed: Sealed rooms have no incoming or exhausted air; their environment must be actively balanced. A sealed grow room takes work to maintain the environment (temp, humidity, CO2, μmol, etc.) using mechanical systems (AC, Lighting, Dehumidifier, Air Quality Management [Bluezone] etc.) and the associated control systems.
Pro: Extreme control provides the best results!
Con: Cost and learning curve.

Hybrid: Hybrid versions of sealed rooms where air is selectively introduced and/or removed. The incoming air should be filtered to remove pathogens and pests. Exhaust air should be treated to remove odors.
Pro: Can provide exceptional environmental control with greater flexibility than sealed.
Con: Cost.

Tip: To test the seal on a room close the room and turn on a sealed exhaust fan. Trace all room edge, windows, ducts, etc. with a burning stick of incense; you will be able to see where incoming air disrupts the upward smoke stream revealing areas needing a better seal. (Remember to sanitize your room after.)

Light Uniformity:

Lighting uniformity (even amounts of light across the growing canopy and under canopy is using inter-canopy LED lighting) ensure consistent maturation times, chemical profiles, and flower quality.
Tip: Lay trellis netting on the floor under your lights to create a grid of the growing area. Use a PAR (photosynthetically Active Radiation) meter to map and record the light levels at a uniform distance from the light source (this should be your target canopy height). Make adjustments to your light hanging locations and heights to achieve your ideal μmol level; this level will be different for each grower based on environmental control and growing style. Larger growers can often have professional lighting layouts provided for free by commercial lighting companies. Growers should plan on providing the target canopy height (finished,) and canopy square footage.


Automating irrigation is one of the easiest ways to improve crop quality, consistency, and free up time. Time saved by automating irrigation can be spent performing hands-on / eye on tasks that improve crop quality and plant health.
Tip: The goal of any irrigation cycle is to achieve uniform media saturation and the leaching of accumulated fertilizer. Target 10-15% runoff on each irrigation cycle. Ensure you have enough drip emitters to prevent channeling; water takes the path of least resistance so water can escape the growing media before uniform saturation.
Tip: Make to use check valves (one-way valves) ahead of fertilizer injection to prevent backflow of fertigation water into your municipal supply.
Tip: Maintain clean irrigation lines with periodic monthly “line shock” treatments using PAA, H2O2, or ClO2 to prevent biofilm formation and clogs.

Humidity Management:

Humidity may be the most overlooked aspect of dialing in a cultivation environment. Growers must manage ambient humidity, transpiration, evaporation, spikes in heat load, and equipment not purpose engineered for cultivation. It is essential to design grow rooms for their total heat/humidity loads.
The Sensible Load: is the energy required to cool the space to the desired temperature.
The Latent Load: the energy required to control humidity by removing excess moisture from the air.
Tip: Size your equipment with 20% buffer capacity; too many growers focus solely on mitigating the heat created from their lights without consideration for the cooling required Use high-efficiency dehumidifiers that incorporate reheat from the evaporative system; this can be save 30-65% of the energy used for dehumidification.

Intentional Stress:

Plants (& some people) thrive under stress. While providing ideal cultivation conditions is the path to growing healthy vigorous plants, controlled stress is the secret to actualization.
Tip: Controlled gradual drought in late flowering has been shown to increase THC, CBD and secondary metabolites. (Note that drought timing had an impact on what terpenes were produced.) Careful experimentation with controlled stresses from drought and temperature can increase your crop quality.


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