What Type Of Light Do Plants Need?

Plants need light to grow. They’re the only living organisms that can form complex starches from the carbon in the air, so they need light energy to make it happen. But what type of light do plants need? Let’s find out the details.

How Do Plants Use Light?

Plants are marvelous creatures that have amazing abilities far beyond what we, humans, do.

They possess the power to turn light into food through photosynthesis. They do it by grabbing light energy using special pigments in their cells and turning the light into chemical energy. These pigments include chlorophyll, which gives plants their green color.

They then use atmospheric carbon in the form of CO2 to turn this energy into complex carbohydrates. The plant will use some of the carbohydrates to survive, and the rest of the food sustains the entire planet.

To put it simply, light is essential for your plants to survive and thrive. That’s why you should provide as much light to your growing leafy babies as you can.

What Type of Light Do Plants Need?

Plants appreciate almost all types of light. The original light source they use is sunlight, which has all the visible (and invisible) light spectrum available to the growing plants.

Most plants require specific wavelengths of light to grow and flower.

  • To aid growth and photosynthesis, plants need blue or violet light. It has a shorter wavelength and higher frequency.
  • To promote flowering, plants need red light. It has a longer wavelength and lower frequency.

The two colors fall on either end of the visible light spectrum and are components of white light sources, like sunlight.

plant growing with sunlight
Plant growing under natural sunlight

White light also contains yellow, orange, green, and other wavelengths that plants utilize. The optimal wavelength range for plants is between 400 –700 nanometers.

In our increasingly cramped living situations, it’s not feasible for indoor plants to have enough sunlight. That’s where artificial assistance comes in handy.

That said, not all artificial light is created equal. Some light sources are more suitable for use as a grow light, while others leave much to be desired.

What Type of Artificial Light is the Best for Plants?

Indoor light fixtures have come a long way since their early days. You can get various colors, shapes, and intensities based on your plant’s needs at a relatively cheap cost. Let’s go over the available types of artificial light:

Incandescent Plant Light

What once was the most common indoor light source isn’t as usual to see nowadays. The incandescent light was the standard for decades until better light sources came about.

Incandescent light bulbs were the result of heating a tungsten coil until it glowed, so they had more than a few problems. The coil was super fragile and broke easily. They also had a super short operating time and died often.

But the biggest downside of incandescent bulbs is the amount of heat they emit. The amount of electricity they turn into light energy is only 20%, with the remaining 80% being lost as heat.

multiple plants under incandescent lamp
High temperature from incandescent light can harm your plants

Aside from being economically terrible, they also harm plants when used as grow lights. Most plants can’t handle being at a close distance to an incandescent light source. They would burn to a crisp at such temperatures!

That’s not all. Incandescent light also covers the warmer end of the visible light spectrum, with more yellow, orange, and red wavelengths. This leaves a gap where blue wavelengths are missing.

All in all, incandescent light isn’t a suitable choice for growing indoor plants.

Fluorescent Plant Light

After the introduction of fluorescent light in the second quarter of the 20th century, more people adopted it into their homes. With a much longer tube lifespan, versatile colors, and relatively cheap operation cost, it was the way forward.

Fluorescent light sources aren’t without their faults, though. The biggest and most obvious was the presence of mercury inside the tube, which would escape and turn to vapor if the tube broke. This huge hazard would be the ultimate downfall of fluorescent light.

The second fault was its limited applications. Tubes were the only form you could get fluorescent light for the first 50 years after their invention. That was before Compact Fluorescent Lamps (CFLs) were invented in the 1970s, making fluorescent lighting more portable.

indoor plant farm with fluorescent lighting
Fluorescent plant light fixtures

In our modern world, fluorescent light is still used, though much less frequently than 20 or 30 years ago. The light fixtures are usually cumbersome and energy inefficient compared to newer technologies like LED.

The main issue with fluorescent light as a plant “grow light” is the opposite of incandescent light. Pure white, daylight, or cool-white fluorescent tubes don’t have enough warm light wavelengths for a flowering plant’s needs. This means you’ll need to supplement it with another type of light.

Warm white fluorescent bulbs are a good choice if you want those warm wavelengths without buying new lights.

High-Intensity Discharge/Sodium Vapor/Halogen

HID lights are known for being the most common street lights until recently. They’re an uncommon choice for indoor lighting because the fixtures are huge and quite noisy.

While they have good light intensity, the color isn’t quite right. Sodium vapor bulbs produce a yellow-colored light that lacks blue light wavelengths, which isn’t ideal for growing plants

LED Plant Light

Last, but certainly not least, we have the newest addition to indoor lighting options; the LED. The commercialization of Light Emitting Diodes (that’s what LED stands for) is a huge step forward for lighting technology.

Just think of how versatile, inexpensive, and flexible LED lighting is. It has solved almost all the issues discussed earlier when it comes to older artificial light sources.

LED lights can be made to emit certain wavelengths of light and not others. Unlike old “spotlight-style” grow lights that had a colored filter masking a white light, LEDs can produce pure blue, red, or violet light.

indoor plants with LED grow light
Modern LED plant light for indoor plants

Innovation of that sort made it that much easier to create zones in your indoor garden for green plants (blue LED light) and flowering plants (red LED light).

You can also very well use white LEDs as a grow light. However, aim for something on the warmer side so you’d get all the wavelengths you need.

One problem that used to make LED grow lights less desirable is that the light intensity was pretty weak. Well, nowadays, LEDs are made in higher intensity options called “high power LEDs.” They should take care of that issue with no problems.

Perhaps the greatest advantage LEDs have over any other light source is how cool they run. There’s almost no need for cooling systems if your grow lights are LEDs, and they can be placed near plants with no danger of scorching them.

How Much Light Do Plants Need?

Depending on the number of plants you have and their light needs, you can easily calculate the number of bulbs to light up a room.

Per square foot, you’ll need anywhere between 20–40 watts.

To determine how much coverage your light bulb gives you, divide the wattage of the bulb by 20 or 40. This should give you the area covered by a single light bulb. Divide the room area by the number you got, and you should know how many bulbs to use.

The calculation above gives you the highest light intensity possible. You can go for something more subtle if need be.