Grow Lighting Part I

The impact that light has on the human eye is different from the effect it has on your plants. Plants take in light to use in the photosynthesis process to convert energy into sugars to consume as food. Different colors of the light spectrum have varying impacts on the quality of your plants, the rate at which they grow, and when they fruit or flower. We had the chance to pick the brain of John G from Sunlight Supply, that was nice enough to share his knowledge and expertise. Come ride the colors of the rainbow with us and John and learn more about how light spectrums and light exposure affect your plants.

Eye Spy With My Little Eye

To better understand what you are offering your plants when flipping that light switch, let’s break down some industry info. We asked John G to give us the lowdown, “The light spectrum is measured in nanometers (Nm)—that’s one billionth of a meter. Typically, when evaluating the light spectrum you look at the realm of 380 Nm to 780 Nm. We call this the lumen scale.”

Well, you only “see” the scale of 400-700 nm with the human eye. That’s why in the industry we tend to say that “lumens are for humans.”

Somewhere Over the Rainbow

The 400-700 nm scale is what we know as primary (red, blue, and yellow) and secondary colors (orange, green, indigo, and violet). Plants can see further into the ultraviolet (<390 nm) and infrared (700+ nm)- the furthest ends of either side of the light spectrum. However, plants do not benefit from these extreme ends of the spectrum.

John G explains that “plants experience infrared and ultraviolet in the same capacity that humans do.” Infrared is perceived as warmth and does not aid in any vitamin or chemical processes and ultraviolet (UV) rays will prohibit growth and can burn and kill the plant, much like overexposure can burn skin.

Mimicking the Great Outdoors

It is a true artist of a grower that can truly mimic the sun. When growing indoors, you are constantly attempting to recreate environmental factors within an enclosed space. From your ventilation system to your lighting, you are trying to mimic both the wind and the sun to trick your plants into believing they are in their natural habitat. Part of mimicking the free offerings of nature is attempting to recreate the seasons for your plants so they know when to flower and/
or fruit.

Plants respond to the different colors of light due to their ability to trigger different stages of the growth cycle.

Plants’ photoreceptors and hormones are affected when exposed to certain spectrums in different intensities. The segment of the light spectrum that plants are responsive to is called photosynthetic active radiation (PAR). PAR accounts for the 400-700 nanometer wavelengths that plants see and utilize for growth and development. When playing with the spectrum that you apply to your plants, it allows you to forgo the use of plant growth regulators that can have potential weird side effects on your plants. By discovering the desired balance of spectrum and the ideal number of “daylight” hours your plants prefer, you can manage growth naturally (our preferred growing method).

Green Doesn’t Mean Grow

Your plants appear green because it is the color of light they do not absorb and reflect. Plants have no use for the color green on the light spectrum and as a result, is the color we perceive with our eyes when looking at them. Plants also appear green due to the chloroplasts in the leaves of your plants that produce chlorophyll and are the energy production system of the plant.

Red Light District

Plants have a photoreceptor that is blue-green in color and called a phytochrome. John G explains that “the sole job of phytochrome is to absorb red light. The absorption of red light will increase your plant’s production of a hormone called meta-topolin.”  This hormone prevents the degradation of chlorophyll in the foliage of your plants and is what allows a plant to stay green during the spring and summer months. The more chlorophyll that your plants have, the higher ability they have to process more energy and promote growth. Red light also helps your plants to determine when to flower and affects seed formation.

The secondary colors on the red side of the spectrum (yellow and orange) have a similar, but less intense, effect than red light would.

Due to the effect that red light has on triggering the flowering phase of your plants you should avoid exposing your plants to red light during their dark period. This means not opening the door to your grow for any reason during their dormant hours or having any other lights within your grow space that may affect them (i.e. power cord power buttons, automated controller LED lights). We recommend covering any lights with black electrical tape to minimize exposure to unintentional light sources. It may seem melodramatic but, just like your emo best friend, your plants are sensitive little souls. The exposure can extend the vertical growth period and put off the flowering phase, which means losing more time until a potential harvest. If your plants don’t move into the flowering phase when expected, it is more time spent on that crop cycle, and more money invested in nutrients, systems, and energy costs.

Blue Hue

Just as with the exposure to red light, plants also have a photoreceptor that uses blue, indigo, and ultraviolet light. The blue photoreceptor is called a cryptochrome. In the presence of elevated blue light, which is typically emitted more by the sun in the fall season, a plant will slow its vertical growth. This is because blue light slows down the production of the hormone called auxin. Auxin is responsible for both root development and vertical growth. When the production of this hormone slows, plants begin to branch out laterally, growing more bushier as opposed to taller.

John G shares that “plants also use blue light to determine how much or how little open their stoma (the pores of the plant responsible for taking in CO2 and emitting water and oxygen). The plants read the amount of blue light present and will use this information to either increase growth or to slow development and go into the flowering phase.“

The far side of the blue spectrum enters into the ultraviolet territory and can be both beneficial and harmful for your plants. Just like the UV effect on your skin, it can cause DNA and membrane damage. However, UV can also increase the production of anthocyanin, which can give your plants a purple hue but also help your plants naturally defend themselves against lethal microorganisms. It is a delicate balance.

Light My Way

Many different light methods have been used in the growing industry. More recently, the norm has shifted towards the use of mixed spectrum lights that are composed of both red and blue spectrums, created to mimic the sun. “Daylight as we call it is full spectrum. The only downfall to daylight is that in some cases it can be too much light. You will notice that many times at the brightest time of the day plants will drop their leaves and shut down photosynthesis. You can see this in garden centers when the plant description tells you how much exposure the plant likes.” -John G from Sunlight Supply.

This balance is best set at a 5:1 red to blue light ratio but many growers still use plant or light transfer methods. By this we mean, either changing out your bulbs from a primarily red to blue light when ready to move into the flowering stage in smaller operations. For larger operations, it is easier to move your plants into a “finishing room” with a higher blue spectrum lighting.

You can create a custom light spectrum by being intentional when combining and choosing your grow lights. When customizing your lighting spectrum, we are big fans of Hortilux bulbs. You can select lights, such as the Hortilux family, to fill your four-lamp or eight-lamp fixture to create a blue-specific formula to use during your veg cycle. We highly recommend the Hortilux PowerVEG T5 lamps during the vegetative stage as they provide a well-balanced spectrum for your plants and also delivers UVA and UVB. UV is an essential component of the spectrum that produces stronger, healthier plants, allowing them to produce higher-quality fruits and flowers. The Hortilux EYE Super HPS grow light is perfect for the flowering/fruiting stage as they provide 17% more total energy and 25% more energy in the violet blue and green spectrum than standard HPS lamps.

If you are looking to create a mixed spectrum fixture, you can combine lamps that will help simulate an outdoor growing environment and allow you to avoid any exchange or further thoughts to your grow lights than routine maintenance. To read more about lighting technology, check out this link to see what may be most beneficial for your grow.

The More You Know, The Better You Grow

Step Into the Light

Your lighting system is an art form to perfect as an indoor gardener. Developing a system for your plants that gets you the most return on investment takes time and experimentation. To help get you there a bit faster there are a few pro tips that can help you develop your lighting system:

• Give your plants a 24-36 hour darkness treatment to speed up your plant’s transition into bloom
• Stick to a rigid 12-12 lighting schedule with no interruptions once your plants have entered their flowering cycle
• Use a light timer to keep your plants on a consistent light schedule and know that schedule so you don’t disturb them when they are sleeping
• Even brief flashes of light exposure during your plants’ dormant hours can cause damage to your plants' cycle and can take upwards of a month to readjust

Lighting is an essential element to creating a quality grow op. By staying informed with our fresh industry information, the more you will come to know how to improve your grow! Keep your eyes peeled for more information about how to choose the right lighting for your grow and how to use it on our blog page.