What LED Lights Work For Plants And Why

LED is the newest lighting technology on the market and many plant growers and owners ask themselves whether it can effectively be used as growing lights for plants. As a matter of fact, LED lights prove to be a very good artificial light source for indoor plants if used the right way.

LED lights work for plants as they typically emit light from 250 nm – 800 nm of wavelength which lies within the photosynthesis activity radiation (PAR) of plants. Besides, LED brightness levels of 300 – 800 lumens best mimic natural daylight intensities if timed according to daylight hours.

I was intrigued to find out that LED lights work so well for indoor plants as they come at lower cost than other artificial lighting systems and in a great variety of bulbs and light colors. In this post, I will share all about what LED lights work best and how you use them on your houseplants.

Can Plants Photosynthesize With LED Light?

Regular LED lights typically emit light from around 250 nm – 800 nm and therefore generally enable plants to photosynthesize under their light. Photosynthesis activity radiation (PAR) of plants lies between 400 – 700 nm of wavelength. Besides, LED brightness levels of 300 – 800 lumens best mimics natural daylight intensities.

Hence, most LED lights generally will work as plant lights. However, if your plants solely rely on LED lights or you really want to make them thrive under LED light, there are a couple of things to pay attention to which I will explain in this post.

LED Lights For Houseplants: Best Imitation Of Natural Light

There are many reasons why LED lights make for great plant lights:

  • Low cost: LEDs use less energy which saves money on electricity bills
  • Energy efficiency: LED lights consume less energy than other artificial lighting types
  • Versatile color range: Full spectrum mimics natural sunlight the best and various colors for various growth stages and effects available
  • Effective: Less LED lights needed to create bright environment
  • Less heat production: LED lights don’t get as hot as other grow lights
  • Customer-friendly: LEDs come in many shapes and sizes and are easy to install at home

Tip: To enhance the positive light effects, you can buy specific LED grow lights for plants which have the most appropriate wavelength coverage and brightness and are sometimes specifically made for certain plant types.

Are There Any Downsides To Using LED Lights On Houseplants?

Even though LEDs are great plant lights, there are some downsides worth mentioning as well:

  • Initial cost: LED lights are generally more expensive to buy than other artificial lights, though they last forever and save you money on electricity later
  • Weight: Some LED grow light systems can be quite heavy
  • Effectiveness of regular LED lights: Obviously, specific LED grow lights have much more effect on plants than regular LED lights do. Though always ask yourself how much artificial light your plants really need.
  • Overexposure and rhythm: Using artificial lights takes proper timing. Do not leave the lights on for more than 8-10 hours otherwise you risk overstimulating and overexposing your plants to light.
  • Natural light beats artificial light all day: From a plant as well as an energy perspective, it is always best to use the natural light available. By using natural light, your plants will be best adapted to its biological as well as seasonal rhythms and there is less that you can do wrong in this regard.

Please Note: Whenever possible, choose natural light sources over artificial lighting as it prepares plants best for seasonal and biological changes. A plant doesn’t need to grow a lot the whole year, it is actually just natural for them to go through periods with less light as well. Make sure to give your plants the seasonal rest they need.

LED Lights That Are Suitable As Grow Lights: What Wavelengths And Brightness You Need

Buying Regular LED Lights: Don’t Trust The Color Only, Always Check The Wavelengths

LED lights come in a great variety of colors. The color temperature of an LED is indicated by Kelvin (K).

In addition, most manufacturers also give their LED colors names such as pink-blue, bright red, purple and so on. This is supposed to make it easier for customers as you no longer have to interpret the Kelvin indications but can choose a lamp according to the color name it has.

The higher the color temperature in Kelvin, the cooler the light appears. Here are some daily-life examples of color temperatures in Kelvin:

  • Embers (orange, red color): 800 K
  • Candles (orange, amber color): 2000 K
  • Daylight (neutral, white color): 5500-6500 K
  • Computer screen (cool, blue-ish color): 6500 K
  • UV light (ultraviolet, invisible to human eye): 12’000-20’000 K

Now that you’ve already learned that plants need wavelengths of 400 – 700 nm which on the electromagnetic spectrum mainly refers to red and blue light radiation, you might think that you can just opt for the red and blue LEDs as plant lights.

Unfortunately, the Kelvin temperature or visible color of LEDs is a false friend. This is due to the fact that each color is usually made up of a combination of wavelengths that produce that certain color. Kelvin light temperature indications therefore cannot be converted into wavelengths.

This is based on the principle of additive color mixing which you might remember from school or if you work with lighting, you will be well aware of this.

What Is Additive Color Mixing? Additive color mixing is a color model that predicts the color appearance of combinations of different light components. The sum of the three primary colors blue, red, and green yields white light. The opposite model is subtractive color mixing of components of light-absorbing materials and the sum of the primary colors red, yellow, and blue yields black color.

Fortunately, most manufacturers mention not only Kelvin but also nanometers on their packaging or at least in the product information sheet. For example in IKEAs online shop, the product information sheet is available at each LED product, giving all specifications you need to know about the LED bulbs.

Ironically, white lamps may cover a better range of wavelengths than purely red or blue lamps as producing white light needs a combination of all colors. Unless you are using a plant light for only a specific stage of growth with very specific wavelengths required, I recommend opting for the whiter bulbs as they cover most wavelengths of normal daylight.

Regular LEDs Or Specific LED Grow Lights?

Most regular LED lamps have an indicated spectrum of about 250 – 800 nm which includes the wavelengths necessary for plant lights – they will work for your plants though best effects are obviously achieved with specific LED grow lights as these are designed to be plant lights.

Regular LED lamps are usually also of warm or cool white tones which are less obtrusive to the human eye then let’s say blue or red lamps – keep in mind that you will see the light emitted by these lamps daily and you don’t want to be distracted by them.

Besides, if you want to go for regular LED lights, I recommend choosing bulbs instead of light strips or fixtures as bulbs are more adjustable to the plant’s position and needs of brightness levels by adapting the distance to the light source.

For more sensitive plants or if you really want to get only the best for your plants, buying an LED grow light is a very good option and is not even that much more expensive than regular LED lights. You can find LED grow lights from SANSI imitating natural daylight starting at 15-20$ on Amazon or from Grow Light on ebay for similar prices.

Tip: When you’re looking for a standard grow light that suits most plant types and growth stages, always look for “Full Spectrum” and “PAR Spectrum” grow lights. Full and PAR spectrum comes closest to natural daylight which means it covers a broad range of wavelengths to best cater for any light needs a plant might have.

Brightness Levels Of LED Lights: Knowing What Lumens You Need For Plants Per Area

As a rule of thumb, LED lights with 300 – 800 lumens (lm) have an appropriate brightness for most plant types. For light-intensive plants such as certain succulents or other sun-loving species, stronger bulbs or specific grow lights can be applied. To know whether your plants need more light than the average 300 – 800 lm, please check the requirements for each plant species before deciding on an LED light.

In regard to brightness of the lights, not only the strength of the light source matters but also the number of bulbs and as well as their distance to the plants.

I recommend installing the light source about 25 – 35 inches (= 63 – 73 cm) from the top of the soil. An average of 500 lm per square foot provides sufficient lighting for most plant types.

Conclusion: LED Lights Work Well For Plants While Best Effects Are Achieved With LED Grow Lights

LED lights work perfectly fine for plants and are an easy-to-use and low cost solution for artificial plant light. Here’s a short but helpful sum up of the main tips to keep in mind when buying LED lights for plants:

Regular LED lights:

  • Check the spectrum of wavelengths (best 400 – 700 nm)
  • Choose bulbs instead of light strips or fixtures (better adjustable to plants’ position)
  • Choose white tones instead of colors (less obtrusive color for daily use and more similar to daylight)
  • Choose brightness of at least 300 – 800 lm
  • Position them at about 25 -35 inches (= 63 – 73 cm) above plants (brighter bulbs further away than weaker bulbs)
  • Provide brightness of about 500 lm per square foot

If you don’t want to opt for regular LED lights, there are plenty of specific LED plant grow lights available, too. Make sure to keep in mind these tips when buying LED grow lights:

  • Choose bulbs that specifically aim to imitate daylight wavelengths
  • Choose brightness of at least 300 – 800 lm or as indicated for the desired plant species
  • Check the specifications of use of the lamp before buying (suitability for what plant species, etc.)
  • Follow the user manual: Do not exceed indicated hours per day and install at appropriate distance from plants
  • Provide brightness of about 500 lm per square foot or as indicated for the desired plant species

With these tips in mind, I am sure you will purchase just the right LED lights to make your houseplants happy!

Can You Use Any Light As A Grow Light For Plants?

As a general rule, any light source that emits wavelengths between 400 – 700 nm and has 300 – 800 lm intensity can be used as a grow light for plants with varying effectiveness. However, specific plant grow lights come with more extensive and intense wavelength coverage best suited to the needs of various plant types as well as growth stages.

Please Note: The color of a light bulb can be misleading as colors are always made of combinations of wavelengths which makes it difficult to judge wavelengths by only color, especially with whiter tones where many wavelengths are covered. Hence, always make sure to check what wavelengths the light source emits.

Is UV Light Good Or Bad For Plants?

UV light radiation is not essential for plants, though studies have shown that exposure to low levels of UV-A and -B radiation can promote faster growth as well as enhance pathogen resistance and production of flavonoids in plants.

Most of these benefits are rather relevant to agricultural crops than houseplants but some UV exposure can also benefit your indoor plants that are stuck in a dark corner.

Read On: If you are interested in using UV light on your plants, make sure to read my post on that topic to know exactly what effects it has and when UV light is good and when bad for your plants.

What Water Is Best For Houseplants?

Not only light is essential to plants but also water. Plant water should contain all the necessary nutrients for plants and preferably no harmful substances.

Generally, rainwater is the best water for indoor plants due to its high nutrient and oxygen levels.

Read On: In my post on plant water, I explain what alternatives there are to rainwater and how to prepare the best plant water possible. Enjoy reading!

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