An Introduction to Green Wall Lighting

Plants are not furniture; plants are living organisms that need water, carbon dioxide and sunlight in order to survive. We all learn about photosynthesis in elementary school, but most people seem to forget this simple science by adulthood.

We don’t have to think about giving our plants carbon dioxide since they take it out of the air on their own and most people remember to water their plants (over- & under- watering is a whole different topic). However, light is the ingredient that is most misunderstood or forgotten and poor lighting is often to blame for dying plants.

Proper lighting is absolutely essential to the success of a living wall, or any indoor plants for that matter. Light is the food that fuels healthy plant growth. Plants without enough light will get thin, lose color, grow “stretchy” and look unhealthy. Unhealthy plants are not attractive. Learning about proper lighting will ensure that your next living wall installation looks like a luscious green jungle.

The goal for my Ultimate Guide to Living Green Wall Lighting is to educate you on the different types of light, how to measure light intensity, light quality and how to select the right light bulbs for your next living wall installation.

First, a quick refresher: photosynthesis is a process used by plants to convert light energy, usually from the Sun, into chemical energy, in the form of a sugar, that can be stored and used later as food for the plant. Try to imagine the plant leaf almost like a mini solar panel. The raw materials of photosynthesis, water and carbon dioxide, enter the cells of the leaf and chlorophyll, the pigment in green plants, absorbs the solar energy. The products of photosynthesis are sugar and oxygen. Here is a simple diagram to help explain:

Photosynthesis

Insufficient lighting is the most frequent cause of living wall failures. We know that lack of light results in unhealthy looking plants, but it also causes the plants to stop drinking water. Because the plants stop drinking, excess water builds up in the soil and creates a toxic anaerobic environment. This damp soil downs the plants and causes root rot. It is also a fertile environment for soil-borne pathogens, molds and bugs, which can further compound the problem.

Since insufficient lighting can lead to a host of nasty problems, it’s imperative that we learn how to properly light a living wall. To do this, we need to understand the different types of light, how to measure light intensity, light quality and how to select the right light bulbs. The science behind can be complicated, so here’s the synopsis for those of you short on time:

What is Light?

Light is actually just waves of electromagnetic radiation. There is a wide range of electromagnetic radiation including X-rays, Microwaves and FM/AM radio waves. What we refer to as light is the portion of these waves which is visible to the human eye. Visible light has a wavelength in the range of 400 nanometres (nm) to 700 nanometres – between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).

Types Of Light

Visible white light is actually a composition of many different colors of light (think of a rainbow), with the primary colors being blue, green and red. Photosynthesis depends upon the absorption of blue and red light by the chlorophyll pigments in the leaves of plants (this is why plant grow lights are red and blue). Plants appear green to us because they do not absorb the green light, so that green light is reflected off the leaves and into our eyes.

Types of Light

Measuring Light Intensity

Light IntensityLight intensity refers to the total amount of light, or the degree of brightness, that a light source emits. The intensity of light is usually measured in lux or foot-candles. Light intensity can be easily measured with any off the shelf light meter and there are many guides for what is the desired lux or foot-candles by plant type. Your eyes cannot accurately estimate light intensity levels, so you need to buy a light meter. In general, it’s pretty difficult to have too much light in indoor conditions, so my opinion is that more is almost always better.

However, lux and foot-candle light meters are meant for measuring the amount of light as seen by humans. They can be used as a rough guide for lighting levels, but they don’t actually tell us anything about how plants will respond.

If you want to learn more about accurately measuring lighting for plants, including Photosynthetically Active Radiation (PAR light) and Daily Light Integrals (DLI), you’ll have to download my free Ultimate Living Green Wall Lighting Guide.

 

Eric Westerduin is a co-founder of Suite Plants, a manufacturer of living wall systems. Eric is a registered Green Plants For Green Buildings trainer and presents the accredited Advanced Living Walls continuing education course to architects & interior designers across North America. Eric earned his Bachelor's degree from Cornell University's College of Agriculture and Life Sciences. To learn more about Eric or Suite Plants please visit www.suiteplants.com

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  • This is a the best piece I have seen on light for plants. It provides appropriate technical detail, but is written in mostly lay terms Of course, much of this is not new information.

    What is relatively new is the availability of LED lights. Clearly, this is the lighting of the future as incandescents are already being phased out and LED’s are even more energy efficient and more versatile than fluorescents.

    What is still unclear to me is just how to recommend LED’s for plants in home and office environments where natural light is minimal or absent. Overhead fluorescent lighting has been standard in most offices for a long time and we know that most low light plants do just fine with that lighting as long as the lights are on for 8+ hours per day.

    When folks go to their local Home Depot to get lights for their plants, I am unclear about just what color rendering and intensity they should look for to benefit their plants.

    Will Creed
    wcreed@HorticulturalHelp.com

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