Plant lights Plant science

Why Are Leaves Green?

Drawing of the blue, red and green light bouncing off a leaf to get to an eye.
Plants reflect green light. Photo: Nefronus.

The simple reason is that plants reflect green light. The visible spectrum, the range of colors visible to the human eye, ranges from blue to red, going through green and yellow. When light of a certain color bounces off an object to our eye, that’s the color we see.

Tomatoes under purple light
Have you ever seen “blurple” LED lights, a mixture of blue and red? Photo: Rawpixel Ltd

Purple LED Lamps

Some will say that if the leaves reflect the greens, it is because it is not necessary for photosynthesis. Have you ever seen purple LED lights, a mixture of blue and red? The idea is that plants would only need blue and red light, because green is reflected anyway. Sounds logical!

The green light penetrates through the forest canopy.Photo: Silverkey (Mickaël Delcey)

Green Light, What’s It Good For?

In fact, 85% of the green light that reaches the leaves is absorbed. It is this remaining 15% that is reflected and reaches our eyes, giving them the signal that the leaves are green. It’s true that blue and red are better absorbed than green. So why should we care about green? There’s a good reason: green light has the particularity of penetrating deeper into the leaves than blue and red light. When the light is of higher intensity, the leaves surface becomes saturated with red and blue. Green light, on the other hand, penetrates deeper and manages to be absorbed. This is also why green tends to penetrate through the forest canopy.

Planter on a wall with full spectrum lighting.
Full spectrum light. Photo: Robert Bolen via Soltech Solutions, Wikimedia Commons.

Full Spectrum Light

Full-spectrum lamps are your best bet for your houseplants. As the name suggests, they cover the entire electromagnetic spectrum. This includes infrared to near ultraviolet. In other words, these are the wavelengths that are useful to plants. Research continues in this area to try to optimize the efficiency of the lamps so that they best meet plants’ needs. Is there something better than full spectrum: yes, absolutely. Though, it has to be said that this will be more useful in a commercial setting than in your living room. Here a simple full spectrum light will do the trick.

While the laidback gardener wants to make things simple, be careful not to simplify information from scientific studies. Before adopting new practices, take the time to become well informed and ask yourself what you really need. Maybe your old fluorescent tubes are still good enough for now?

Garden writer and blogger, author of 65 gardening books, lecturer and communicator, the Laidback Gardener, Larry Hodgson, passed away in October 2022. Known for his great generosity, his thoroughness and his sense of humor, he reached several generations of amateur and professional gardeners over his 40-year career. Thanks to his son, Mathieu Hodgson, and a team of contributors, will continue its mission of demystifying gardening and making it more accessible to all.

1 comment on “Why Are Leaves Green?

  1. Lakewood Exterminating

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