High Intensity Discharge (HID) Grow Lights encompass three types of lights: Metal Halide (MH) High Pressure Sodium (HPS) and Light Emitting Ceramic (LEC). HID lights have been traditionally used for growing cannabis for many years, and are capable of producing impressive yields. However, HID lights have a particularly high operating temperature. Excess exposure and improper usage of HID lights may result in damaged plants, specifically from the excessive amounts of heat that is produced. Growing cannabis typically requires anywhere between a 12 to 18-hour light cycle, so having the lights being turned on for hours on end will inevitably produce large amounts of heat that can damage your plants.
The Importance of Temperature
Because cannabis grows optimally at a temperature between 68F and 82F (though it will vary for each strain) this heat can cause problems for your plants. The heat produced may dry out your soil quicker than you can water, causing other deficiencies. Dry growing mediums prevent your plants from taking up the require nutrients and can then cause deficiencies such as iron, potassium or magnesium. Depending on how often you are able to tend to your plants, you may not be able to keep up with the rate of evaporation that is occurring due to the increased temperature in your grow space. Spending extended periods of time in dried out soil can cause irreparable damage to your plants.
The heat irradiating from the bulbs can cause direct heat stress on your plants as well. This is typically visualized by yellowish or brown spots, or the serrated leaves curling upwards. Heat damage is especially traumatizing to plant sin the flowering stages, causing massive damage to your buds. Excess heat during flowering can also cause fox-tailing which produces thin, airy buds as the plant tries to produce a new bud on top of the damaged one. If you are growing with HID lights, you will definitely need to be venting or exhausting this heat somehow to avoid these issues, which is also an added expense to your grow space.
Potential For Damage
High temperatures can also trigger root rot in cannabis plants. Root rot is caused by various organisms such as bacteria, fungi or other parasites. The excessive heat can provide an optimal environment for organisms to begin colonize the roots of your plants, causing root rot. There are several symptoms of root rot, and the symptoms may be similar to that of other stresses to your plants. HID lights can contribute to the chances of your plants developing root rot due to the high temperatures that they produce.
The Safety of LEDs
Because LED grow lights produce much less heat than HID grow lights, most growers have started to move towards using LED grow lights more and more. LED grow lights have their own set of drawbacks of course, but their lower heat output helps them to avoid the issues we have outlined above. HID lights are obviously tried and true, but if you’re not careful your plants may be susceptible to damage from their excess heat output.