Before explaining the different grow light options in this industry, allow us to give a better understanding of what light is and how the plant uses and process light naturally from the sun.
First of all, there’s something called spectrums, which are also called wavelengths or dimensions. We normally can’t see these wavelengths as they travel through the air, but you can after it rains—when you see a rainbow in the sky you are being given an opportunity to see what plant “see.”
The purple, orange, red, yellow, indigo, blue and green colors you see in the rainbow are all different wavelengths that are given off by our sun. When talking about plants, however, we are primarily interested in the reds and blues. These are the colors that are absorbed by plants (the other colors—in particular, green—are reflected, which is why plants appear green).
And know that we know what plants absorb, we need to know how the light is processed inside the plant. Light is needed for three different processes. Phototropism triggers the plants ability to turn toward the sun. Photoperiodism is the plants’ reaction to the amount of daylight it receives (most of the time, this will control when the plant is in vegetative or a flowering state). The last process is photosynthesis, which absorbs the energy and converts it onto sugars for food.
So, how do plants get this light when they are inside? Lamps, of course! At this point in time, there are five basic lights in the hydroponic industry. These general lighting options are fluorescent/induction, metal halide (MH), high pressure sodium (HPS), LED and plasma lighting. Each of these lighting systems reacts to the plants slightly different; how these lights are engineered the plants will absorb the energy wavelength differently.
Let’s talk about fluorescent lighting first. You can use this for rooting clones, seeds, vegetative growth, flowering and supplemental lighting. The style lighting I would recommend in the fluorescent family is T5. These, for the most part, run cool and are inexpensive.
Another type of florescent lamp is induction lighting. Induction lighting uses an electronic ballast to create a high frequency that generates a small amount of energy. It then sends that energy around in oval shape tube where it slowly reacts with the mercury in the tube to create a dangerous ultraviolet light.
Because ultraviolet light is still a part of the spectrum of light we generally don’t want a lot of, an inventor named of Nicola Tesla used a phosphorus compound to change the spectrum of light generated by the initial reaction with the mercury in the tube.
Now, more than 100 years later, we’ve used advancements in technology to better tune the phosphorus levels and quality in order to alter the ultraviolet light into the spectrum plans ideally to grow under. The light generated by the induction light is then maximized by its unique shape—the light is generated throughout the tube instead of a single point, making every surface of the tube a light source.
The reason why fluorescent technology last longer than other lighting sources is because there is less moving parts that can break. There’s no soldering, no arc tubes, no fragile wires and no worry about oil on your hands. Also, fluorescent lighting turns on very slowly.
Now, let’s look at metal halide (MH) lighting. It is used mainly for the early growth and vegetative period since they produce more of a blue spectrum, which mimics the sun’s rays during spring and summer. Some growers will also use MH lighting during their flowering stages of growth because it gives off some ultraviolet light, which helps most plants produce more natural oils, typically making the plant more valuable.
High pressure sodium (HPS) lighting gives off a Kelvin range of 2,000 to 3,000 K, which is best for the flowering or fruiting stage of a plants growth cycle. The color that an HPS produces is an orange-to-red spectrum, mimicking the sun’s rays during the late summer and fall. This color, along with the proper light schedule, aids the plants in producing flowers or fruits while they prepare to die off during the winter.
The HPS is the most popular lighting set-up for all indoor gardens. Many gardeners will use only an HPS bulb for their entire cycle in order to save money, as well as maximize their turnaround time. These growers typically will keep their plants in a vegetative state for short periods and then quickly induce fruiting or flowering. Based on this method (which is extremely popular for indoor growing), the HPS bulbs will be used more than MH because the flowering cycle will typically be much longer then the vegetative cycle.
Also note, a HPS bulb is typically smaller and skinnier compared to a MH bulb. This is important to note as some ballasts are made to only power HPS bulbs, which means you would need to purchase a MH conversion bulb. These are specifically made to work with HPS-only ballasts, as well as produce the correct color spectrum in order to achieve a great vegetative cycle.
LED grow lights are a great new technology that ended up getting a bad reputation because the market wasn’t ready for them. When they first entered the market, they were slapped with huge price tags and even larger claims. That caused many people to shy away, especially once the claims were clearly false. So, let’s focus on the facts surrounding LED grow lights.
LED stands for light emitting diodes. Nearly all LED grow lights are good for 50,000 hours of light—that’s six solid years. Along with the bulbs lasting longer than many other grow lamps, you will typically have a much cooler light when you use LED systems—on average, they operate 300°F degrees cooler than other lighting sources. Keep in mind that newer technology LED lights are becoming more intense and they produce enough heat to cause issues, depending on the growing situation. As such, proper ventilation is still required in order to achieve great results.
As mentioned above, our plants use very specific colors of light and do not use all colors to grow. This is why LED lights are a big advantage. They are able to provide specific colors that our garden needs to grow vigorously. However, no matter how many proper colors you have in your light, this does not mean proper colors will always beat a higher intensity.
LED can be a great choice, especially for gardeners who understand the long term over the short term. LED advantages are not always seen immediately; however, they will be noticeable after some time as money will be saved in the long run rather than in the short term. Also, LED grow lights are a new and developing gardening technology; they will continue to get better and better.
Plasma lighting is the newest technology in the indoor grow light world. They were created in order to produce results just as good as the traditional HID systems, but to give you those results with less maintenance involved. The big advantage, aside from cooler light fixtures, is that plasma is more efficient at converting electricity to useable spectrums for your plants (in other words, other systems produce more heat than they do light for your plants).
Also, these new lights do not require bulky equipment, making them easier to work with. On top of this, they do not contain mercury, so it can be argued that they are more earth-friendly then other grow lights. Of course, they also last much longer than other lighting systems, giving them an advantage by lowering your on-going gardening costs when it comes to replacing equipment.
As you can see, there are many choices for indoor grow lights and they all have their advantages and disadvantages. No one is better than the other, so just take a look at what you’re growing and how big your budget, and see which lighting type would be best for you.