Lighting Systems
Watch the following video and read through this page to learn about LED grow lights and their utility inside a classroom growing environment.
(1 minute, 16 seconds)
Video Transcript: LED Grow Lights
Why Use a Lighting System?
Photosynthesis is the process by which green plants use sunlight to create food for themselves. During photosynthesis, oxygen and carbon dioxide are turned into sugar in the presence of light energy. To grow during GTS’s academic year we must supplement outdoor sunlight with another type of light the plant can use.
Lighting Systems in GTS
There are two different lighting systems used in the GTS curriculum.
Outdoors we use sunlight. Because we know going to have decreased sunlight length and decrease sunlight intensity growing outside during the academic year, we try to select a growing site that will capture the maximum amount of sunlight.
Indoors we use artificial lighting. Artificial lighting is generally provided by LED panels. Supplementing natural light with LED lighting allows you to grow plants indoors faster than they would otherwise grow outside during most months of the year. These panels are optimized to grow plants. You may see basic LED panels with just white light. White LED bulbs contain the full spectrum of light needed to grow plants. However, sometimes LED panels include blue and red bulbs as well to achieve faster and more efficient growth. Red light causes plants to elongate and grow faster. Blue light slows down growth and makes them grow stockier.
Compact fluorescent lights can be used as grow lights as well. If you to to buy a compact fluorescent light, it is recommended that you choose a “daylight bulb,” as opposed to a “cool white” or a “warm white” bulb. Daylight bulbs generally have the greatest intensity. Whereas LED lights are typically rated for 50,000 hours of functional use, compact fluorescents generally fatigue to where plants can detect decreased light intensity in about 3 to 5 years. They will need to be replaced at this time.
You may be tempted to use incandescent lights. These lights may seem bright to us, but they actually do not have the amount of light intensity needed to grow plants.
Light Length and Intensity
LED panels need to be put on a timer. You want to make sure you are light is delivered for the length of time needed by the plant, not just at the intensity needed. A timer is often set to keep the light on for 15 or 16 hours per day. If the timer is be set for more than this the plants will not have the necessary rest period needed for healthy growth. On the other hand, when the timer is not set long enough, you can encounter leggy plants. Leggy plants can also be caused by a lack of light intensity when if plants are too far from the LED panel.
If you suspect your timer is not working properly once it is set up, check that you are not bypassing the actual timer component, where it’s just like an on/off switch. If this is happening your plants will generally be stressed and probably bolt or go to seed rapidly and not have a normal growth phase.
One way to ensure your light intensity if great enough for your plants is to keep them close together. Tabletop LED light panels have a set minimum height which may be further away from the seedling than needed. You can use books or a box to get shorter plants closer to the light, lowering the plants as they grow. Ideally, the plant should be kept 3 inches or so from the light, but this recommendation will depend on the plant. For example, lettuce requires much less light intensity when compared to tomatoes.
Selecting a Grow Light
It can be tricky to pick the right lights for growing indoors because there are so many options. Vegetables require more light compared houseplants and other shade-tolerant plants, so you will need to look for a light that is specifically rated for use with vegetable plants. The term “grow light” is not necessarily accurate enough to describe the light you need. Even if the light has blue and red light, it doesn’t mean the light is going to be optimized for vegetables because it’s not just the color, but the intensity, that is important to consider.
Setting up Your Grow Light
It is not recommended to set up an LED light panel by a window. A spot by a window could create a chill that is not favorable to the growth of the plants. Also, the small amount of natural light provided by the window will not create enough light to be beneficial for growth.
Please click NEXT at the bottom of this page to advance through the module. To return to the list of modules, PC users click “Modules” in the top left corner, App users click the back arrow in the top left header.
