Leaf Surface Temperature - The Overlooked Variable

Is Your Thermometer Leading You Astray?

Do you know the temperature of your leaves? When growers convert to LEDs, it’s fairly common to use only a standard thermometer to evaluate if the space is warm enough. But leaf surface temperature is something that is often overlooked, mainly because growers no longer have to worry about the environment overheating.

If you’ve previously grown crops under HPS, HID, or CMH lighting, then you have a strong understanding of how these infrared energy bulbs place your plants at an increased risk of overheating. Airflow becomes incredibly important so that those sweet, sweet buds are kept cool and protected. In fact, for a lot of growers, one of the primary reasons that they move to LEDs is to eliminate the risk of overheating.

The lack of infrared energy with LEDs alleviates the fear of temperature-based leaf burn and airflow issues. However, did you know that leaf temperature can provide you with vital information about your plant and what it needs to thrive?

Although your crop will not overheat under LEDs, growers should still pay attention to the leaf temperature. These plants no longer have a heat source beaming down on them, potentially leaving the leaves a little too cool, and in turn, impacting the plant’s growth.

Maintaining Ideal Leaf Temperature

Why does it matter? One of the roles that leaves play is collecting and converting the energy in the plant through photosynthesis. This is where the surface temperature of the leaves can make a difference, as the optimal temperature for the photosynthesis process is a stable 28˚C or 82.4˚F.

Photosynthesis is a complex process, with several factors impacting its overall efficiency. However, the temperature is one property that growers can control fairly easily by maintaining proper airflow and making adjustments to the HVAC equipment. Understanding the leaf temperature of your cannabis plants will equip you with essential knowledge about your grow environment so that you can make any necessary adjustments.

Selecting The Right Thermometer- Why Just a Few Degrees Matter?

Standard thermometers don’t tell you the whole plant story. This is because only a portion of the sensor is touching the actual leaf; an average thermometer is not designed to pinpoint small regions, like leaf surface area. Instead, the temperature that is measured is often that of the air surrounding the plant (not of the leaf itself) which could cause you to make adjustments to your environment that are not necessary.

This is why every grower should have an IR thermometer or Laser Thermometer in their toolbox.

IR thermometers will accurately provide you with a digital readout of the temperature of the surface it’s pointed at, providing you with an accurate picture of the leaf's surface temperature.

We understand that HVAC settings automatically adjust based on the air temperature and that it’s simply not practical to make manual adjustments to your entire system each time the leaf temperature misses that 28-degree mark. So, why does it really matter?

Using an IR thermometer regularly can provide you a deeper understanding of what air temperature is needed to reach that ideal leaf surface temperature. Once you discover the average air temperature, you can then use this information to adjust your entire system.

But it doesn’t stop there; several factors can alter the temperature of the leaf surface. When you regularly monitor and record this information, you will begin to learn how the leaf temperature reacts throughout your space, and each grow cycle. This deeper understanding will provide you with the information that you need to make small adjustments to your growing environment including airflow, light height and/or intensity, and air temperature, allowing you to cultivate the ideal growing environment and yield more consistent buds.