What Is A Grow Light?

Plants need three very basic things to grow: water, nutrients and light. Light is used in photosynthesis. It’s when plants take light energy, usually from the sun, and turns that into chemical energy.

The relationship between lights and your plants

Chemical energy is what’s stored in the bonds of chemical compounds, like atoms and molecules. It’s the potential energy of a chemical, called such because it’s got the potential to make energy during a chemical reaction. When a chemical reaction happens, heat is usually one of the by-products.

Chemical energy is what your plants need to create other certain chemicals that attribute to the best yields. It’s also why they need the sun. While outdoor growers worry about how much sun their plants get, indoor growers have to worry about what types of bulbs to get, how close to place those lights over their plants, and how long those lights should be kept on for.

Let’s break it down and talk about just exactly how plants absorb light…


Lumens is a unit of luminous flux, which is the measure of the perceived power of light. This just means that it’s a way to figure out how much power we think light emits. Lumens measure the total “amount” of light emitted by a light source that is visible to us, describing the amount of light that’s radiated by a light source.

This is different from a candela, which indicates the strength of the light. It is also different from a lux, which indicates the illumination intensity of an area. Lumens describe how much light there is in a specific area. Lumens aren’t something you can see; it measures the total light sent out by a light source.

Distance makes the plant grow slower

Plants grow faster and stronger when the grow lamp is closer. That’s why BCNL grow boxes position the light source 2.5 feet away from your plants.

That being said, it’s important to keep in mind that double the light, does not equal twice the penetration.

Light penetration is most efficient when your plants aren’t massive so its lower leaves can get that good stuff from the light source, too.

This is why having a huge grow box may not be the most efficient thing. While, yes, plants end up growing very tall, those lights have to be placed higher up, increasing the distance between them and the roots of your plants.

See the rainbow

You may remember ROY G BIV from your elementary school days. It’s the varying wavelengths of light spectrums.

This matters because depending on what stage of photosynthesis your plant is in, it’ll absorb different colors, in varying amounts. Your plant needs to see the rainbow because your plants’ growth is separated into two phases: vegetative growth and root growth/flowering.

Vegetative growth requires the blue end of the spectrum (420-550 nm). Root growth and flowering requires yellow, amber, and red from the spectrum (550-750 nm).

The colour spectrum

Color is calculated as “temperature,” on par with heat. Increased color temperatures appear “cooler,” and lower temperatures appear “warmer.” The unit of measurement for color temperature is the Kelvin (K).

To encourage flowering and growth in height, your plant needs a lower temperature that’s simultaneously warmer – an orange/red that’s at 2700K and below. Vegetative growth requires a greater temperature that’s cooler, around 5000K and above.

In order to replicate the sun, you ideally give our plants a mix of both cool and warm color, heavier on the blue and some orange/red.

Each light is unique

A number of different grow lights are used to target the numerous ranges of the color spectrum. These grow lights fall under four categories: High Intensity Discharge (HID), fluorescent, incandescent, and LED.

HID lights

There are two major types of HID lights – metal halide, and high pressure sodium.

  • Metal Halide (MH) – these are great for leafy plant development, as this HID bulb stresses the blue end of the spectrum that ranges from 2700-5500K. If you only have one kind of grow light, this is the best option, as it is closest thing to natural sunshine.

  • High Pressure Sodium (HPS) – this is an HID bulb that is great for blooming, but not foliage, delivering orange-red color temperatures around 2200K. Note that you should never use this bulb by itself, but rather, to use it together with MH bulbs or as being a supplement to natural sunlight.

Fluorescent lights

Fluorescent lights contain different color ranges and intensities. Standard fluorescents or high-output fluorescents may have warmer and cooler temperatures and can be utilized in combos.

They can be placed closer to the vegetation because they give off low heat. As far as performance is concerned, fluorescents come close to HID bulbs when utilized effectively. Though they are less intense, they are also more affordable.

Incandescent lights

Incandescent lights aren’t the most ideal option as they burn hot, and therefore can’t be positioned close to vegetation.

In essence, it’s the least similar to natural light. If your mind’s set on incandescent lights, though, you can find color-corrected incandescent bulbs in the market.

LED lights

The newest grow light selection obtainable. Recently developed, some LED grow lights tend to be said to cover the entire color spectrum for plants, and produce very little heat, to allow them to be put near to the crops.

For this reason, this most likely are not probably the most cost-effective choice given that they’re truly costly in fact it is even now arguable regardless of whether LED generates much better outcomes than grow lights that are standard.