Education Guides

Maintaining Healthy Indoor Cannabis Plants

With much of the conversation centering on yields, potency, and other key performance indicators, it’s easy to lose sight of the fact that every grower’s goal should be to make the plants as happy as possible.

And unless they’re able to establish a framework that ultimately gives the plants the best possible shot of growing to their fullest potential, finding success using crop steering and other cultivation techniques will be that much more difficult.

In this article, we’ll explore why the best way to grow indoor weed really comes down to one thing: maintaining healthy indoor cannabis plants.

Environmental Conditions

Creating an ideal indoor environment will go a long way to set plants up for success right from the start. It may seem counterintuitive but one of the first things to consider before outfitting a facility with new equipment is the outdoor conditions. An operation located along the Northern California coast will have very different heating and cooling needs than a facility in Las Vegas, after all.  Outdoor temperatures and humidity impact indoor conditions and therefore must factor into the decisions operators make well before the first clone can be rooted in. 

Air must be optimal to support transpiration rates, and because different growth phases have varying temperature and humidity needs, cultivators must be prepared to make adjustments in real time. In earlier growth phases, for example, the plants may benefit from the cultivator adding humidity to the room. But as more biomass gets produced throughout later growth phases, the cultivator will need to remove some of that humidity.  Shooting for an ideal vapor pressure deficit (VPD) range is a more reliable way to maintain environmental control than focusing on relative humidity. This awareness can help lead growers toward finding the right equipment – fans, dehumidifiers, air conditioners, and more – to maintain proper airflow and humidity.

Lighting is another key component. Supporting the plants’ ability to photosynthesize means trying to replicate the intensity of the sun in an indoor environment using human-made equipment. Cannabis plants love light, and while trying to match the sun’s output of 1200-2000 micromoles per day may be out of reach, keeping lighting conditions hovering around 900-1300 can do wonders for managing electricity costs and optimizing for quality. But intensity is just one factor; growers should also consider how the lighting spectrum impacts each phase of plant growth, and whether LED or HPS lights work best for their plants and their setup.

The availability of CO2 also has a direct impact on overall plant health and growth performance. Outdoor gardens benefit from the CO2 generated by humans, animals, and industrialization in ways that indoor setups can’t. As a result, growers may need to supplement rooms with CO2 throughout the plants’ life cycle.

Then once these parameters are set up to create the best possible environment for the plants, an effective irrigation system will help tie it all together.

Root Zone Conditions

Plants need more than a completely optimized environment to thrive; growers must perform similar due diligence when establishing proper conditions in the root zone. And this starts with cultivators deciding the best grow medium for their indoor grow – a choice that usually comes down to three categories: soil, soilless/hydroponic, or aeroponic.

Soil is an organic medium packed with living organisms that break down nutrients for plants to process. This nutrient availability supports healthy growth in ways that growers can’t control – from the amount of resources available to those organisms, to whether the organisms are alive and actively processing, to the timeline of when they release the plant-soluble nutrients. Outdoor plants in soil naturally adapt to these and other changes in their own time. But soil is such a complex medium that without an understanding of soil biology, cultivators could wind up not being able to maximize their outputs as much as they should in an indoor environment. The inability to control variables is the primary reason why soil is typically not the first choice for indoor commercial cultivators.

Soilless hydroponic media like Rockwool and coco are commonly used in indoor cultivations and are known to require fairly consistent irrigation, usually via flood and drain systems or drip stakes. Between different hydronic substrates there’s a lot of variety, but the main appeal for growers is the ability to adjust root zone conditions when necessary. Which soilless medium to choose ultimately depends upon factors like their ability to take in nutrients and oxygen, overall quality and cost, and environmental impact. 

With aeroponics, there’s hardly any medium at all which means there’s zero buffering capacity in the event of water or power loss. Changes to nutrient composition can impact crops instantly in aeroponic setups and cause severe plant health issues within hours if not addressed quickly. The unforgiving, inflexible nature of aeroponics is why they are least commonly seen in commercial indoor cultivation. 

After selecting a substrate, growers must determine which cannabis fertilizer for indoor plants will work best for their crops. Where historically cannabis cultivators have relied upon fertilizers formulated for a veriety of crops, options have expanded in recent decades to include formulations optimized specifically to address the needs of the cannabis plant. Mixed nutrients can be a great option for small-scale operations, while larger operations might opt for two-part salts which can be diluted and used in fertigation. Nutrients can add up to be a fairly expensive output for cannabis producers and have varying impacts on operational considerations like water usage and waste management. But when factored against labor, rent, and energy costs, making the right nutrient decisions for the plants is well worth it in the long run.

In Summary:

  • Outdoor temperatures and humidity must factor into a grower’s decisions when working toward creating the optimal indoor environment for their plants. 
  • Each growth phase has its own temperature and humidity needs, which cultivators must be prepared to address in real-time.
  • Understanding intensity and the lighting spectrum can go a long way toward helping growers choose the best lighting for their plants. 
  • Creating the best root zone environment starts with choosing the best grow medium type: soil, soilless/hydroponic, or aeroponic.
  • Tying ideal environment and root zone conditions together with intentional irrigation and nutrient programs will go a long way to set plants (and growers!) up for success.

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