How To Decide What Grow Lights to Use

The trend of legal cannabis means that it is possible in more than half of the country’s states to legally purchase cannabis for medicinal use, and in a growing fraction of those states, for recreational use as well. But the do-it-yourselfers out there (and the consumers on a budget) may be interested in growing their own weed.

There are a lot of decisions to make if that’s the road you want to take. If you’ve already decided that you want to cultivate an indoor garden, it’s time for you to think about the type of lighting you want to use. In nature, cannabis plants only have one option: the sun. Cannabis grown outside is subject to lots of different variabesNaturally grown cannabis responds to the environmental variables the outdoors surrounds it with, but the most important of these variables is light. Cannabis typically receives the greatest amount of light during its vegetative stage, the stage when the plant’s foundation for a bountiful harvest is either fortified or diminished. Once the winter approaches and cannabis is in darkness for a longer amount of time, or the plant is exposed to as much darkness as it is exposed to light, it begins to flower.

One of the benefits of cultivating an indoor grows is that technology has made it possible for growers to take what they know about cannabis’ natural growing cycle and manipulate the light to optimize their yields. The more light cannabis absorbs, the larger a yield it can produce. As in all plants, light is used to catalyze the process of photosynthesis.  Photosynthesis is the mechanism by which plants create glucose, the food that supports healthy plant growth.  Applying this knowledge to choose the right combination of grow lights and use them strategically can result in a bountiful yield. Different grow lights produce unique results, require different maintenance, and vary in cost. This article will give an overview of each lighting option.

Fluorescent Lights 

Fluorescent lights are a popular choice for growing cannabis indoorsThese lights have been used to mimic the sun for as long as plants have been cultivated indoors. While it is possible to create a similar effect to the sun’s, doing so requires the use of several types of fluorescents, and that can get expensive. These lights are not the most efficient sources, and using them can lead to a hefty electricity bill. You can maximize their light by using reflectors.

There are two varieties of fluorescent lights used for growing: CFLs and T5s. CFLs are the lights that look like short spirals. In order to produce the best results, CFLs must be placed only about 5 cm away from the top of a plant.  This makes them ideal for small growing spaces such as closets. T5s come in panels, but they can still be used in very close proximity to the plants. Fluorescent lights are cheap, ideal for small spaces, and only become expensive when used in bulk. However, fluorescent lights produce smaller yields than other grow lights and do not have a powerful enough reach to penetrate through the height of tall plants.

HIDs (High-Intensity Discharge Lights) 

These lights were created for use in large public spaces like stadiums. Because of their power, they are often used by cultivators for indoor growing. The most useful type of HIDs for cannabis cultivation are high-pressure sodium vapor light and metal halide. High-pressure sodium vapor lights (HPS) are particularly useful during cannabis’ flowering stage. 400w or 600w HPS lights are the safest choices for indoor grows since they distribute light evenly and have a low risk of overheating your plants. These are arguably the most popular type of grow light because they produce the greatest yields per watt of electricity than any other type. Metal halide lights create the ideal spectrum for cannabis’ vegetative stage. They can be used for the flowering stage as well.

HIDs get really hot, so it’s best to use them in conjunction with a ventilation system. They are typically attached to an exhaust to keep temperatures down. Because of the attention growers must give to heat management when using HIDs, novices tend to be wary of trying them.

LEDs (Light Emitting Diodes) 

LED lights can be used to growWhat LED lights lack in quality, they make up in savings. LEDs use energy efficiently and without generating too much heat. LEDs are also a great choice for those who want the utmost discretion. They are silent and don’t emit the infrared heat used to detect HPS lights. While LEDs can be much more expensive than more conventional lighting options, they last longer than their counterparts and their efficiency will save money in the long term. Small LED lights need very little set up which makes them a much easier alternative to HID lighting. Finally, anecdotal evidence suggests that the combination of HPS and LED lighting yields more potent bud.

One of the greatest cons to using LEDs is the distance required between the lights and the plants. LED lights should be kept at least 18 inches away from the tops of plants, making LEDs impractical for growers confined to a small space. The best LEDs to get are those that contain full spectrum light. LEDs that only contain red and blue light will yield plants that are vulnerable to nutrient deficiencies.

Strategize Your Lighting 

It isn’t enough to purchase a lighting system to reap the benefits of indoor lighting. First, think about how you are placing your plants. If they are bunched too closely together, the leaves will block one another out and stymie the productivity of photosynthesis. Ideally, the plants should be placed so that they are not blocking light from each other and so that they are each receiving approximately the same amount of light from the light source. Using reflectors will help to make sure that the plants are exposed to as much light as possible.

To protect your plants from overheating, make sure that the temperature in your grow space does not get hotter than 80 degrees F. Fluorescent lights can be placed 2-4 inches away from the plants. Metal halide and HPS lights at 400w should be placed about 12-16 inches away from the plants. LED lights should be about 18 inches away from the plants.

Safety Warning

Finally, be safe. Depending on your grow space, you may be using a lot of power, and that can result in fires, shocks, outages, and surges. Since you’re growing a plant, you’re also going to have the electricity powering these lights nearby water. Make sure that your wires are protected from any potential water spills. Placing your wires above ground will help to keep things safe in the event of a flood.

Dianna Benjamin

About the author: Dianna Benjamin is a freelance writer, teacher, wife, and mom horrified and fascinated by social justice and our inability--yet constant pursuit--to get it right.