It is commonly known amongst growers that plants require various types of light for
good quality growth and high yields. In fact, plants require the light that happens at both
higher and lower wavelengths, called ultraviolet and microwaves. All light, both invisible
and visible, fall on a spectrum measured in nanometers, which represents the
wavelength of the light. As indoor growers, we focus on the spectrum between 400-700
nanometers, commonly referred to as Photosynthetically Active Radiation (PAR). To
simplify the concept, in general, plants will require more light from the blue side of the
spectrum, or 400 nanometer side, during their seedling and developing foliage stage.
While plants will require more light from the orange side, or 700 nanometer side, during
the blooming and flowering stage.
Understanding efficiency in energy consumption and the photosynthetic benefits must
be considered when studying the different types of grow lights available in today’s
market. To decide what lighting to use for your grow room setup, one must
comprehend the differences between the variety of grow lights available. Researching
and understanding their features and benefits along with their limitations is vital. We
know that learning about the various types of grow lights can be a bit overwhelming,
primarily for those new to cultivation. Let us help by breaking down some of the most
important facts, both positive and negative, about the different lighting options.
Fluorescent Grow Lights (CFL)
Compact Fluorescent Lights (CFL’s) are one of the most common options you will see
in the market. These lights are available in most home improvement stores and even
some grocery stores have them in stock. CFL’s are perfect for small grows and are the
most affordable lights available. They are ideal for starting out. These bulbs have
standard sockets, which means you can use them with any standard light fixture without any special equipment. You will need two different bulbs,
6500K, also known as daylight or warm white, and 2700K which is a more red colored
light. 6500K bulbs are used for the seedling and developing foliage stage, while 2700K
bulbs are used for the blooming and flowering stage. A standard CFL bulb is very
affordable and is expected to last about one year. You can expect to yield about 12
grams per light, per grow.
HID Grow Lights
Also known as gas or discharge lights, High-intensity discharge lights (HID’s) are mostly
produced as metal halide (MH) or sodium vapor lights. High-intensity discharge lights
work by passing electricity through a gas-filled tube. HID lights provide the brightest light
compared to the other lights discussed here. HID lights have been used by growers for
many years being that they are about 10 times as efficient as traditional incandescent
lights that offer little blue light, and burn too hot. However, although more efficient, HID lights also emit a lot of heat. HID lights also require big and costly fixtures to operate them, although the bulbs themselves are fairly inexpensive. Keep in mind that they are not the grow light of choice by most growers operating with reasonably small grow rooms. It is
recommended to use a combination of both MH and HPS lights if the crops being
yielded are blooming or fruiting crops. Both MH and HPS lights can be operated
together and alternated, depending on the stage of growth and you will likely
see better results by using both. Although HID bulbs are not interchangeable, you can
use a conversion lamp to attain the spectral output of an MH lamp
in an HPS fixture.
HPS Grow Lights
High pressure sodium lights (HPS) have been a popular choice with indoor growers,
over the past few decades and are known to be the most common type of grow light
used in the commercial greenhouse industry. HPS lights usually last for about
10,000 hours of use, however changing them at 18 months of use is common practice,
even if the 10,000 hours has not been met. This is mainly because the quality and
quantity of light produced weakens after the 18-month span. HPS lights get extremely
hot and they should not be placed too close to the crops or they will burn the foliage.
Always make sure to keep HPS lights away from anything flammable including any
shade or paper material. Moreover, growers using HPS light as their sole source should
know that the crop will not receive anything from the blue spectrum of lighting. In fact,
most commercial growing facilities only use HPS lights as a supplement to natural light.
Among the multiple HID lighting choices, HPS lights are equally as energy efficient as
MH bulbs, but far more efficient in their photosynthetic worth.
Ceramic Metal Halide Lights
Ceramic Metal Halide (CMH) grow lights are a variation of MH lights with a combination
of HPS added to the mix. The difference being that CMH lights use a ceramic tube, like
the ones used in HPS lights, as a substitute to the quartz that is used in customary MH
lights. The ceramic tubes will operate at higher pressures than quartz glass tubes,
allowing manufacturers to make the variations on the spectrum, more precise than
previous technologies allowed.
Light emitting diodes (LED’s) have now become the grow light of choice for both
professional and hobby growers. LED lights are capable of emitting light in wavelengths
ranging from 250 nanometers to more than 1,000 nanometers.
As previously mentioned, most plants require wavelengths of light ranging from the blue
side of the spectrum at about 400 nanometers to the orange side of the spectrum at
about 700 nanometers. LED’s are special in that we can manipulate the spectrum of
wavelengths, with the same bulb, as needed for the lifespan of the grow. Compared to
other grow lights, LED’s have the longest lifespan lasting more than 50,000 hours.
Moreover, LED lights do not need additional equipment such as reflectors, because the
light is emitted directly towards the plants. Although LED lights have so many
advantages, the drawback is in the price, as they are the costliest of the options.