All About What Kind of Light Plants Need

In their natural habitat, each plant type grows in spots where it gets the right amount of sunlight to meet its light requirements. For houseplants, things look a little different as natural sunlight is not always available indoors in the right amounts. Luckily, sunlight isn’t the only light source that can make plants grow.

Blue and red light with correspondent wavelengths between 400 – 700 nm is the kind of light plants need the most. These wavelengths are also termed as photosynthesis activity radiation (PAR) as they stimulate plants’ photosynthetic processes.

Once you understand what kind of light plants need, you can make your plants thrive even in darker corners of your living space. Read on to find out what you need to look out for considering the light requirements of your plants and you will brighten up your plants’ days in no time.

Photosynthesis: The Reason Why Plants Need Light in the First Place

Light is one of the essential needs plants can’t do without, as we probably all know. This has one major reason.

Plants are able to produce their own food (at least partially) through a chemical process called photosynthesis. Carbon dioxide (CO2) and water (H2O) react through light energy which produces sugar (glucose).

Glucose is the base of a plant’s metabolism. Without it, plant bodies would be unable to work the way they do. Plants convert glucose into cellulose to build cell walls and into starch that is stored as a food source.

Reading Recommendation: Light is not the only essential ingredient to a happy plant life! Check out my post linked here to find out what else plants need to live and grow.

The Kind of Light Plants Need: Mainly Red and Blue Wavelengths

What kind of light plants need is not limited to light sources but rather depends on what kind of wavelengths the light source consists of. Not all light contains the same wavelengths. Let’s first delve into a bit of light theory to better understand what light plants need.

Light consists of varying wavelengths of the electromagnetic spectrum. The full spectrum comprises the full range of electromagnetic radiation (= waves) that exists. It goes from the longest wavelengths of several kilometers such as radio waves all the way to very short wavelengths of 100 nanometers or less such as UV light or gamma rays.

Each wavelength has a certain color. The human eye is only able to see light in the range of about 380 – 700 nanometers; all other wavelengths remain hidden from view for us. Hence, what we define as visible light goes from violet, blue, green, yellow, and orange all the way to red light. Ultraviolet or infrared light is already invisible to our eyes while some animals can still see it.

Theory Explained: For those interested, I’ll link a well-explained short Youtube video here on the electromagnetic spectrum which gives great examples to better understand that concept.

Plants are similar to the human eye: Not all wavelengths are useful to them. Generally, plants need red and blue wavelengths (400 – 700 nm) for photosynthesis. This is also called the Photosynthesis activity radiation (PAR) of plants and is often indicated on grow lights.

Do Plants Need Sunlight or Just Light?

Now, given that a plant needs mainly red and blue light for photosynthesis, does any light source do the trick or does it only work with sunlight?

If the appropriate wavelengths are covered by the light source, not just sunlight but any light source will do for plants.

You can use any artificial light covering a good part of the spectrum of red and blue wavelengths (best are full spectrum lights) that have the right intensity. There are plenty of specific grow lights available and some of them are easy to install and do not cost a fortune either.

What I just want to mention here is that some of these artificial lighting methods can be quite strong, especially if you buy specific plant grow lights. Make sure you use them as indicated and do not exceed the maximum lighting hours. Whenever possible, I recommend using natural daylight for your plants.

If you want to learn more about what benefits artificial light sources have and how to use them correctly, check out my posts on UV as well as LED light as grow lights which I will link for you right here:

Short Wrap-Up: Not only sunlight works for plants but also artificial lightings such as LED, UV light, incandescent or fluorescent lights, and other grow lights.

How Much Light Do Your Plants Need?

Appropriate lighting of plants does not only depend on what kind of light your plants get but equally on how much light they get each day as well as throughout the year.

Depending on the plant type, indoor plants need approximately 12-16 hours of light each day which is the equivalent amount of light they would get growing outdoors in their natural habitat. Plant species that prefer sunnier spots need more while shadier plants need a little less.

You should also consider the intensity of light according to plant type. If using artificial lighting, make sure to set up a lighting routine, turning the lights on and off always at the same time each day.

Darkness is just as important as light: Give your plants about 8 hours of rest in complete darkness. Also, take their dormant phase into consideration and adapt artificial lighting in wintertime when your plants naturally are less productive.

Tip: I recommend installing an automatic timer for artificial lighting that includes dimming the lights in the mornings and evenings. This best imitates natural sunrise and sunset.

Full Sun or Half Shade: What the Tags on a Houseplant Really Tell You About its Light Requirements

When you buy a houseplant, they usually come with a tag or label specifying the plant type as well as what its watering and light requirements are. The specifications are fairly short and do no more than give you a hint at what that plant really needs in terms of light such as full sun, half sun, half shade, and shade.

Here is a little more explanation of what each label means with regard to the light requirements:

Full Sun or a Sun Symbol: The Sunbathers

If the tag mentions “full sun” or has a sun symbol indicated this means that this plant type loves direct sunlight. Those plants are true sunbathers and can’t get enough sunlight.

They should get at least 6 hours of direct sunlight while more is always better.

When placing these plants in your home, choose the sunniest spots closest to windows and where nothing obstructs direct sunlight coming in (such as curtains or a tree outside the window).

Half-Sun or Half-Shade: The Allrounders

Plants that come labeled as “half-sun” or “half-shade” can do with both a bit of shade and a bit of sun. The symbol for this label varies a little. Sometimes it is represented as a half-blackened sun or circle, other times it is depicted as a sun partially covered by clouds.

These plants will grow well in various spots in your home.

To make these partially sun-loving plants happy, you can place them anywhere where no intense midday sun can burn them. They are fine with morning or afternoon sun combined with some indirect light as well as spots that may be partially shaded due to obstacles such as trees outside or the occasional light curtain drawn.

Full Shade: The Darker Side of Plant Life

Even though light is an essential need of plants, some plants just love the murky corners.

Full shade is usually depicted either by a cloud symbol or by a blackened circle or sun and it means this plant type doesn’t tolerate much direct sunlight at all. Such plants are sensitive to direct sunlight, especially in summer when the sun’s rays are strongest.

Make sure that these plants are in a spot that gets no midday sun and generally no more than 3 hours of direct sunlight per day. They will do well in places a little further from the windows that only get indirect or diffused daylight.

How to Tell if Your Plant is Getting Enough or Too Much Light?

Depending on where your plants are in your living space, they might not get the appropriate amount of light needed to thrive.

  • Not enough light: If your plant doesn’t get enough light, you will notice that it doesn’t grow much at all and is rather stagnant. It will also look a little leggy and grow very lopsided toward the light. Any new leaves will remain smaller than average and probably show an unusual color.
  • Too much light: Especially too much direct sunlight can leave its traces on a plant. If a plant is close to a window and you start noticing scorched patches or yellowing, curled up edges of the leaves, then the plant is probably getting too much light or light that is too intense.

Good to Know: A regular health check for your indoor plants is recommendable. You can easily integrate a health check into your weekly watering routine. In this post linked here, I’ll show you what steps to take and what to look out for when checking your plants.

Do Plants Need Drainage Holes?

Drainage holes are essential to a plant’s well-being as they help regulate waterflow through the plant pot. No plant likes to sit in water constantly and without drainage holes, excess water will just get stuck in the soil.

In my post on why plants need drainage and how to create good drainage in any type of pot, you’ll learn all you need to know about this plant-essential method!

How to Water Indoor Plants?

A healthy plant needs water regularly. But don’t overdo it! One of the most common plant care mistake is overwatering. Plants don’t need as much water as we generally assume.

Learn more about how to water your houseplants the right way through this link.

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