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The Different Grow Room Lights and How You Use Them

Part I: An Overview

Let there be Light

In general, a grow room needs light, light, and more light. The indirect lighting many houseplants do fine with won’t work in a grow room.

Mimicking sunlight

What types of light work best for grow rooms? Those that mimic natural sunlight. You’ll get the best grow room harvests when you have periods of strong “sunlight” followed by periods of darkness . Plants will not flower without adequate periods of both light and darkness.

In this first article of the series, we’ll talk about the different kinds of light, briefly. Subsequent articles will go over each in greater detail.

The most common types of grow room lights

High Intensity Discharge (HID) lights

The most common grow room lights are called High Intensity Discharge (HID) lights. There are two kinds of HID lights: Metal Halide (MH), and High-Pressure Sodium (HPS). There’s also a “dual spectrum” light that combines MH and HPS properties in one bulb.

High-pressure sodium bulbs (HPS)

HPS bulbs are comparable to MH bulbs, with good spectral distribution, but they lack the metal halide’s intensity at the “blue” end of the light spectrum. HPS bulbs are best used as plants are starting to bud, and can carry through the flowering stages of growth.

Metal halide bulbs

Metal halide (MH) bulbs are a long-time favorite among growers, because they provide an excellent spectral distribution. For plants, this is optimal for growth, because MH bulbs mimic bright summer sunlight – and that means that photosynthesis also occurs at high “natural” levels, much more than other types of lights can achieve. These are good for your plants when they’re in their green growth, vegetative state.

Dual spectrum bulbs

Dual spectrum bulbs contain both the workings HPS bulbs and MH bulbs within a single bulb. You can use these during all stages of growth, in that this is a true full-spectrum bulb.

Fluorescent lights

Compact Fluorescent Lights (CFL) and Fluorescent Tubes can also be used in grow rooms. They are cheaper and easier to set up and maintain than HIDs, are good for young plants or clones that don’t yet need a lot of light, and are best for very small “grow rooms” with just one or two plants that don’t exceed 12 inches in height. However, yields are lower than with HIDs because fluorescents just don’t have the intensity of the high power lamps.


Light Emitting Diode (LED) lights have made their way into many grow rooms. Although still developing and relatively new to the scene, growers have been impressed with their performance thus far.

We address the benefits and drawbacks of each in greater detail throughout the series. Check out the next article: HID lights.