All the Light Science You Need to Know to Grow a Plant – LED Grow Light Basics

According to your fifth grade science class a plant needs three things to grow:
  1. Energy from Sunlight
  2. Carbon Dioxide from Air
  3. Water from Soil.

Quick Review of Photosynthesis (and I mean quick)

Let us talk about photosynthesis. If you can stretch your mind back to fifth grade, then you’ll remember that plants are amazing because they can produce food for themselves. They take carbon dioxide and water (not foods) and use the energy from sun to turn these “not foods” into sugar (foods).

If a plant can’t go through the process of photosynthesis, then it will die. What does this mean for you? It means that you need light to turn the “not foods” into “foods”. Simple, right?

All the Light Science You Need to learn about LED Lights

You need light to grow your plants. Well, you have various choices (all are good):

  • The Sun (a very popular, free light that many plant growers utilize)
  • High-Intensity Discharge Lights (HIDS). Not as popular as the sun, but still popular.
  • Metallic-Halide Lights (MHs) Great Lights
  • High-Pressure Sodium Lights (HPS) Great Lights
  • Fluorescent Lights Great Lights
  • Light-Emitting Diodes (LED) My personal favorite (yes, I’m biased )

Generally, people use sunlight to grow plants because of the price-savings. Scientists and your average gardeners have found that other lights like LED lights can be used to grow plants as well. Many people have had success growing plants using LED grow lights.

The sun’s light contains a variety of different colors. Plants, for the most part, absorb the red and blue light put off by the sun and reflect the other light (as illustrated below). Plants reflect green light and that is why they appear green to us. The sunlight and other growing lights take out light colors that aren’t required by the plant. LED lights could be fine-tuned to just create the light plants need.

Because of this control over the light output by LED lights, they are said to be “more efficient” than traditional lights. This means they provide the plant what it needs without even as much waste. There are many science behind this, but all you really need to know is that LED grow lights consume low energy and last longer than traditional grow lights.

Red and Blue Light Basics

The blue light helps the plant grow big, green, and tall (the vegetative stage) and the red light helps the plant flower and produce vegetables, or whatever it is the plant is producing. Most LED grow lights come with both reb and blue light now so they can grow your plant from start to finish.

Hours of Sunlight

So you understand the fundamentals, but you most likely want to know how many hours every day should the light be pointing in your own plants? The truth is it depends on what you’re growing. I’ll provide you with some general advice though. I recommend 6 hours of darkness and 18 hours of light during the germination stage (when the plants are just seeds). After the seeds sprout from the ground, move it to 8 hours of darkness and 16 hours of light. When the plants grow and start flowering, it’s not a bad idea to switch them to a 12 hours off, 12 hours on schedule.

This pattern mimics the sun (that big free light in the sky). The nearer to winter it gets, the less the sunlight shines. The diminished amount of light acts as a warning sign for plants to “get a move on it” and start flowering and yielding their vegetables or fruits.


Now all the light science you need to know to grow a plant. Do yourself a favor and quit researching more about this. I know that sounds pushy, but I’ve seen too many men and women get bogged down now in their own plant growing journey. People spend hours and hours researching when what they actually have to do is learn the basics, move on, and start growing and experimenting. Move on to step two by reading my following article about determining which type of grow light is best for your situation, choose the type that you think most closely fits your situation, purchase the thing, and for heaven’s sake start growing (this is where you will find the true happiness that comes from gardening).

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Charles Selvage
Hey, this is Charles Selvage Hollywood, CA. I have 5 years experience about gardening, planting, and others. If you have anything to know, please email me here.
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