Many growers know the best way to grow cannabis indoors is to mimic outdoor conditions. But do you know you actually have an edge? Since the outdoors can be very unpredictable, consider the power to regulate factors such as hydration, lighting, and humidity that are crucial to a healthy crop.

Light, and the heat created by natural light, is one of the most important areas of focus. But the impact of light goes beyond different frequencies and hours of exposure. Because lighting can produce a significant amount of heat, just like the sun, it can evaporate nutrient-rich water from your grow, resulting in excess humidity—which can have a large impact on the health and yield of your crops.

Let’s explore a few basics on this relationship between lighting and humidity with the help of Anden experts Kirk Collins, Major Accounts Sales Manager, and Victoria Aceves, East Coast Regional Sales Manager.

Light Sources and Humidity

Light is obviously an essential component to growing and maintaining plants. The heat that comes with natural and artificial light plays a role in the humidity levels of any given growing room.

When growing outdoors in the wild, plants are equipped to deal with daily sunsets and temperature drops, which results in fluctuating humidity at night. However, excess humidity is able to evaporate into the atmosphere. In grow rooms, your indoor plants will likely maintain a consistent temperature during the day. But what about at night?

When the lights are off at night, temperatures are lower, so the air conditioner won’t kick in to remove any moisture. According to Aceves, “the shift in temperature can be as great as 30-40 degrees Fahrenheit,” causing condensation to form on the walls of your grow space.

Collins says that this is “a highly important time to monitor environmental conditions.” Keep dehumidifiers running to offset the overnight rise in humidity, which can help prevent mold and bud rot.

Light Placement

Another factor to consider when designing your lighting is the location of your light sources in relation to your crops as well as your dehumidifiers. Light intensity, or how much light and heat is received by a plant from its light source, increases as the light source gets closer to the plant.

As a light source gets further from the plant, light intensity decreases. While each plant is different in how much light it actually needs to thrive, the concern with cannabis is how much humidity it will emit and how that will impact the humidity regulation in the room. The intensity of the light will determine how warm the plant gets and, therefore, how much humidity it will produce.

The specific ideal distances for lights in relation to your crop depends on its growing stage. According to Aceves, “lower intensity lighting can be closer and higher intensity lights must be farther away.”

For instance, seedlings will thrive when growing lights are stationed between two and three feet above them. In the vegetative stage, however, the light can be as close as one foot above.

Collins says, “as the plant grows in height towards the light, it acclimates to the intensity.” Though, it depends on the type of lighting. “The lack of ambient heat from LED fixtures allows the plant to grow within inches of the fixture, whereas HID fixtures would burn the plant at that distance,” Collins notes.

When adjusting light placement, you must also consider how close it is to your HVAC equipment. It is not ideal to have your dehumidifier unit sitting below your light source as they will block the plants from receiving the light needed to grow. Aceves notes that “dehumidifiers are best located either hung from the ceiling in the space above or beside the lighting fixtures, on the ground with enough clearance for the drain tube, or on a shelf designed to hold the weight.”

Type of Lighting

If you’re an experienced grower, you know that you can’t just pick out any portable dehumidifier from the hardware store and expect great results. Similarly, you can’t just stick any light bulb you want above your crops. There are a number of options for grow lights, but you should consider how different types of lighting will impact HVAC performance.

HID Grow Light

While LED lights are now the most utilized for indoor growing, some still opt for the traditional High Intensity Discharge (HID) lamps. This option has a lower upfront cost than LED lights, but require bulb changes every 6 to 12 months, and higher ceiling heights as a greater distance is needed between canopy and fixture due to the heat emitted by the fixture.

LED Grow Lights

More growers today choose to use LED lights as opposed to other traditional options. LED lights emit less heat than HID lights, meaning their proximities to the plants are more consistent and manageable. Of course, since LEDs do not give off as much heat, the plants need to be more closely watched, as some may tend to place the lights too close to the crops, typically causing bleaching. Collins explains, “bleaching does reduce the quality of the flower and creates an undesirable end product. Bleaching is a key indicator that the lights are too close or too intense.”

So, what do our experts have to say about your choice of light?

“HID lights provide forward directional heat”, says Aceves, “meaning the plants ‘feel’ the heat on the surface of the leaf and therefore are triggered to transpire. LED lighting tends to produce heat off the back end, which means the plants need to be monitored so that they are triggered by the atmospheric differential in vapor pressure, or VPD.”

They both have their merits, and it’s really up to the grower!

Know more. Grow more.

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