What Color Light Is Best For Plant Growth

Today we will learn what color light is best for plant growth, all you need to know about plant growth with light colors is here.

The use of artificial light for indoor plants is a great solution, especially if we do not have those wonderful and large windows that we often see in decoration magazines. 

They also allow us to make early seedbeds or grow exotic plants, even in a basement.

But the question is that many times we can feel quite confused when it comes to knowing which are the correct lamps that we should use in each case or in general. 

Today’s note will try to make this information clearer, we will talk about the requirements of the light of plants and wavelength and color spectrum of different artificial light bulbs to decide which are the most suitable bulbs for our indoor plants.

The natural light of the sun contains the full spectrum of light including all the colors of the rainbow. Plants use all this spectrum of colors present in sunlight, the most important being red and blue.

There are many options on the market for choosing an artificial light for houseplants, including special lights for growing plants called “grow lights” or “broad spectrum lights.” 

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Without a doubt these last ones are the best, since they will give our plants all the colors they need and it is the most similar to the sunlight that we can find. However, if they were not available for any reason, we can put together our own play of light so that our plants grow healthy indoors.

In the following image, you can see the wavelength of each type of light, with a graph that shows the color spectrum. We will take sunlight as an ideal and thus we can compare with the spectra of the different lamps most used.

If you can not access a so-called broad spectrum lamp, what I would do is a combination of a warm white LED, this way we can provide a wider spectrum, low temperature and a really low and economical consumption.

The right intensity

The intensity of artificial light that a plant receives is determined by the power of the bulb and by the proximity between the spot and the light source.

Just as each plant differs in its need for certain colors of light, they also need different intensities. In general, those plants that come from tropical climates or shady forests do not require as much light as those that grow in dry and sunny climates.

Most flowering houseplants, such as begonias and African violets, are happy to be about 25 to 30 cm away from the light source.

Plants grown for their foliage, such as ivy or philodendron, can be placed up to 90cm away from an artificial light source for houseplants.

However, many flowering plants, such as orchids and gardenias, as well as most orchard and citrus plants, require a higher light intensity to flourish and bear fruit.

Anyway, when we talk about the distance between our plants and the light source, it is important to consider what type of lamp we are using, incandescent lamps, for example, produce a lot of heat and could burn the foliage, but fluorescent lights, almost they do not emit heat, so they can be closer to plants.

The right duration

No matter what type of plant we are growing, they all need a break.

During the dark hours, plants breathe, which is a fundamental part of their growth process.

This resting time affects many biological processes of plants, including their growth rate and the production of new shoots, fruits and flowers.

Botanical experts usually divide plants in general into three large groups according to the number of hours of light they need per day, basically these groups are:

Short day plants: such as chrysanthemums, kalanchoe, azaleas and begonias. These types of plants thrive on less than 12 hours of light per day. In fact, these plants necessarily require a period of even shorter days to start their flowering process.

Long-day plants: require between 14 and 18 hours of light per day. Most seasonal vegetable and flower seedlings are long-day plants. When they don’t get enough light, they pale and grow “lanky.”

Neutral day plants: geranics, coleus, African violets and foliage plants in general, are usually satisfied with 8 to 12 hours of light per day throughout the year.

What and how much artificial light for indoor lighting do I need?

Fluorescent lights produce two to three times more light than incandescent bulbs with the same power consumption. They are the most economical lights for interior gardening and also have a much longer useful life than ordinary lamps.

Broad spectrum fluorescent lights produce a balance between warm and cold light (red and blue) which allows the natural solar spectrum to be reproduced fairly accurately.

Anyway, as I mentioned before, we can make a combination between cold and warm LEDs or (fluorescent and incandescent lights) to imitate this type of lamps and thus, provide artificial light for indoor plants more efficiently. You can use a ratio of 3 to 10, that is, for every 30 watts of warm light (spectrum with more reds), provide them with 100 watts of fluorescent or cold light (spectrum with more blues).

As a final guide to choose the type of light and its intensity, an initial idea may be to use lamps that provide from 200 to 400 watts, ensuring that they are at a distance of no more than 40 centimeters. But as always, each plant has its requirements, so this choice will also depend on the type of plant you are growing.

The formula

I have found a formula, to determine how many watts we need to light a certain space. The formula is in “square feet” but the final result will be passed in meters.

This formula mentions that as a general rule, we could need between 20 and 40 watts per square foot (1 ft2 = 0.092 m2). Entoces proposes to do these two accounts:

1000/20 = 50 and 1000/40 = 25

The answer to this formula indicates that with a 1000 watt system it could efficiently illuminate between 25 and 50 square feet, which in meters would be between 2.3 to 4.6 square meters.

Let’s also remember that both the lack of lighting and its excess, can be harmful to our plants. So the following table can help you identify if you are providing artificial lighting for indoor plants in the wrong way:

Signs of poor lighting in your plants or seedlings.

Excess light:

The leaves wrinkle and the edges turn brown or brown burn spots appear.

Small leaves lose the green color to become too whitish.

The plant becomes sad, it loses vigor in the hottest hours of the day.

The plant orients its leaves towards the opposite direction of light.

Lack of light:

The leaves turn yellow and fall.

Plants barely bloom and when they do, the flowers are often incompletely developed or too small and often fall before flowering.

The plants develop stems that are almost colorless, too long and thin, with little vitality and with a great distance between the internodes and that extend in search of the light source.

Its development is slower and weaker.

What color light is best for plant growth

Plants use sunlight to make energy. The process by which they do this is called photosynthesis. Chlorophyll in the plant is the pigment that absorbs light. Light is made up of three different colors: red, blue and green. The reason that green plants appear that color is that they reflect that color in the light spectrum. In other words, the chlorophyll in the plant absorbs the red and blue light much more readily than the green light.

How does green light affect plant growth

Professor Kevin Folta of the University of Florida has produced experiments in which plants’ development, especially as seedlings, is actually harmed by green light. Specifically, he found that green light can reverse the stem growth in certain plants.

Daniel Mosquin, the education and technology manager for the University of British Columbia Botanical Garden and Centre for Plant Research, also gave as his opinion that green light, though it might not cause plants to actually die, will have detrimental effects because of the lack of photosynthesis that will result. The red and blue lights are the ones that produce the energy needed for photosynthesis and plant growth and development.

How does red light affect plant growth and why is red light good for plants

 Red light can convey caution or danger or stopping at intersections, but for plants red light is highly effective at regulating growth and development. Within the photosynthetically active waveband (400 to 700 nm), sunlight emits roughly similar amounts of blue, green and red light. With conventional electric lamps, the proportion of light is somewhat similar, ranging from 24 percent for coolwhite fluorescent to 40 percent for high-pressure sodium (HPS) lamps. With arrays of light-emitting diodes (LEDs), the proportion of red light can range from 0 to 100 percent. Many commercial LED fixtures developed for plant growth applications emit a large proportion of red light, with 75 to 85 percent of the light spectrum commonly emitted in the red region. The primary reasons why LED fixtures emit a lot of red are 1) red LEDs are among the most efficient at converting electricity into photosynthetic photons, 2) chlorophyll strongly absorbs red light, thus it is effective at photosynthesis, and 3) red LEDs are relatively inexpensive. Let’s take a brief look at how red light influences plant growth and development. 

Red Vs. Green

Experiments have been recorded showing the difference between plants grown under red and green lights, respectively. A simple demonstration of this was at the 2004 California State Fair, where Nichele R. Lee presented a project with the title: “What Color Light Helps Plants Grow?” The conclusion was that the red light grew the stronger plants, though it was noted that the green light had plants that germinated more quickly.

A study of the effects of red and green light on plants was conducted by Lewis H. Flint and Charles F. Moreland at Louisiana State University. The pair studied and compared plant growth with red and green lights, but specifically simple leaf development of intact and decapitated bean plants. Decapitating the bean plants reversed some of the effects the different colors of light were having on the plants.

How does white light affect plant growth

White light is great for plants. I mean, think about it. What color is sunlight?

It only makes sense that providing artificial light that has a similar spectrum to natural sunlight would work well for plants.

Plants need mostly red and blue light for photosynthesis. White light, like sunlight, contains large amounts of red and blue wavelengths. But it also contains large amounts of green, yellow and every other color.

Because plants absorb primarily red and blue light, those other colors go mostly unused. In the case of the sun, that doesn’t really matter, since it is an endless energy source.

How does yellow light affect plant growth

Plants make the least use of yellow light, but they do use it as well. Give them some, but they won’t need much. Just keep in mind yellow light exhibit less growth for plants compared to blue and red light 

How does Violet light affect plant growth

On its own, violet light has a limited effect on plant growth, but it is very useful when combined with red and blue light. The addition of violet light enhances the color, taste, and smell of plants. It does enhance the color, taste, and aroma of plants.

How does orange light affect plant growth

A plant can have one photopigment devoted to absorbing deep blue, another devoted to absorbing yellow, another for orange, and another for red.Orange light is used like red light. It is not the ideal wavelength that a darker red is, but it is still absorbed like red. You want to provide some orange light, but more light that is a darker red than orange.

Advantages Of LED Grow Lights

Are there substantial advantages to using an LED system as opposed to HID lighting for your indoor grow?

Actually, yes.

LED grow lights have become popular with growers for good reason — they offer many benefits that other lighting systems don’t. Advantages of choosing LED lights for growing plants indoors include:

  • Efficiency
  • Temperature
  • Lifespan
  • The spectrum of light they provide
  • Their size

Greater Efficiency

Nearly every grower who recommends using LEDs for growing plants will talk about the efficiency of such a lighting system. LEDs are in fact way more efficient than HID lights, which translates to lower utility costs for you.

Cooler Temperature

LEDs run significantly cooler than HID bulbs. HID systems can become extremely hot, putting crops at risk of heat damage, and can even become fire hazards when they’re used in small spaces. (Learn more about the importance of moderate grow-room temperature here.)

Longer Lifespan

LEDs offer more than just improved efficiency and cooler temperatures. You’ll also get more grow hours out of your LEDs — a lot more. LED grow lights typically last for 50,000 hours or more, whereas HID bulbs generally last 10,000 to 18,000 hours, depending on the specific type of bulb. When it comes to longevity, there’s really no competition.

The Full Spectrum

A major advantage of using LED grow lights is the huge spectrum of energy they provide. When you choose LED, you don’t have to worry about switching out lights as your crops mature through their growth cycle. Even better — you can actually install a system that’s tailored specifically to the type of crop you grow.

Less Bulk

Are you growing in close quarters? If so, that’s another reason to go with LEDs, which have the distinct advantage of being able to fit into smaller, tighter grow areas. This advantage goes hand in hand with the cooler temperature of LEDs — not only can you create a more compact grow room, but your crops can grow fairly close to the lights without the risk of heat burn.

Keep in mind that heat burn isn’t the same as light burn — being too close to any type of light bulb puts your crops at risk of suffering from light burn. Reduce the chance of your crops facing light burn by keeping them within the ideal distance from your LEDs — 12 to 18 inches.

State Rebates

Another perk of choosing the LED route is that you could end up saving a good amount of money. Both the federal government and local municipalities issue rebates on LED lighting systems as a way to incentivize growers to invest in energy-efficient models.