When growing indoor plants, you need to think about your lighting needs. And while natural light is ideal for plants, it’s not always an option. So when considering artificial light for plants, some growers are debating a grow light vs. regular light. In this article, we’re looking at this debate, going through what’s best for plant growth, providing options for indoor lighting, and giving basic information to help you make the most of your indoor gardening experience.
Table of Contents
- 1 Why Use Regular Lights?
- 2 Types Of Lights: Definitions
- 3 How Do Plants Use Wavelengths?
- 4 What Do We Mean By Regular Light?
- 5 Here’s Where It Gets Tricky: PAR Vs. Lumens
- 6 Can You Convert Lumens To Par?
- 7 Do You Actually Need Complex Conversions?
- 8 Did You Know?
- 9 Which Regular Lights Work For Indoor Growing?
- 10 What Plants Grow Well Under Regular Light?
- 11 How Do I Know If My Plant Is Getting Enough Light?
- 12 How Close Should My Regular Light Be To My Plants?
- 13 How Long Should I Have My Lights On My Plants?
- 14 Conclusion
Why Use Regular Lights?
Before we get started, I’m going to make some assumptions about why you’re reading this. There are a couple of reasons you might want to use regular lights instead of grow lights.
- You already have a lot of regular lights and don’t want them to go to waste
- You’re new to the indoor gardening space and want to dip your toe before committing (i.e., you don’t want to spend money on grow lights yet)
- You’re not able to afford grow lights
- You’re curious if the wavelengths can create similar results as traditional grow lights
These are all completely legitimate reasons for the discussion of grow lights vs. regular lights. That said, for the most part, regular lights (we’ll define what this means in a second) aren’t going to have as good of intensity – or a great of light wavelengths – as most modern grow lights.
That’s not to say there aren’t some use cases for regular lights in the indoor gardening space. In fact, several regular light bulbs and lighting fixtures produce significant blue wavelengths – which is suitable for foliage growth, seedlings, and seed germination.
So while, holistically, grow lights are the winners in the grow light vs. regular light competition, this article is going to be more about what you can do – not necessarily what’s the most optimum for plant growth for commercial indoor gardeners. And for a lot of indoor growers, this is enough.
The Youtube channel Gardening in Canada does an excellent job of laying out the conversation:
So let’s dive into the definitions of regular lights vs. grow lights.
Types Of Lights: Definitions
We should begin by saying that there are many types of lights, and under each category, some lights have been manufactured to produce better results for plants. Let’s go through the differences of each to give you an overview of the lighting space.
This is the classic light that some of us still use at home. With this type, electricity is passed via a filament, which heats up and produces light.
Options in the incandescent category produce a lot of red light but don’t generate much blue light. Because of that, they’re a pretty poor option for growing plants. They also emit a lot of heat, so they’d need to be further away from the plants to protect them from burning.
Although there is still some healthy debate over which lighting type is ideal for indoor cultivation, no one thinks regular incandescent bulbs are still a viable alternative. And, while LED light products improve year after year, incandescent light has mostly stayed the same.
Halogen lights are an enhanced version of incandescent lights. With this form of lighting, electricity goes through a socket and travels through a tungsten filament. The main difference between halogen and incandescent lights is that halogen bulbs have halogen gas, while incandescents have argon gas.
Because of this, halogen bulbs shine a little brighter and last longer than incandescent alternatives. Halogens are considered 20% more efficient than incandescents.
Fluorescent lighting encompasses CFLs, linear fluorescent tubes, T5 bulbs, T8 bulbs, T12 bulbs, and other types of fluorescent lighting. Stores, schools, workplaces, and even indoor gardening employ this adaptable lighting solution. Electricity enters fluorescent fixtures through the ballast and feeds into the metal pins on both ends of the fixture to produce light. The gasses react as the voltage passes down the tube, creating light visible to the naked eye. Fluorescent lights are less expensive to buy, have a smaller carbon footprint, and are more energy-efficient than incandescent bulbs. And T5s are well-known for supporting seed germination.
In terms of regular fluorescent tubes, they’re a surprisingly effective artificial light source for some plants at home. As a whole, they a cooler – both in color and temperature. Standard fluorescent bulbs work well for some indoor plants, specifically low-light plants.
Ceramic Metal Halide Lights
With ceramic metal halide lights, an electric current runs through metal halide gas and mercury, producing light. This option falls under the high-intensity discharge umbrella. It has a high-quality light emission that is 3-5 times more efficient than incandescent lights. However, they take a long time to heat up, so unlike LEDs, you won’t be able to turn on the light right away.
High-Pressure Sodium Lights
HPS systems were the industry standard for commercial growers because they are less expensive, have a higher intensity, produce a lot of red light.
HPS lights also produce a lot of yellow light, which is why they’re commonly employed for security and street lighting. Because of their enormous outputs and broad color spectrum, HPS lights were chosen by indoor and greenhouse growers for many years. It’s not been until the last few years that LEDs have started dethroning them as the king of the grow lights space.
LEDs are the up-and-comers in the field of grow lights. They’re practical, energy-efficient, and getting cheaper every year. Two semiconductor materials, one charged positively (protons) and the other negatively (electrons), make up LED lights. Energy is emitted in the form of a photon when these two particles clash. The hue of the light is determined by the amount of energy released. The light is then focussed and directed in a precise direction. An LED grow light is well-known for generating a large amount of light, particularly full-spectrum light.
Regular LED lights are becoming more common in homes, as they last longer and are more energy-efficient. Entire countries are beginning to phase out halogen and incandescent bulbs to lessen their overall national carbon footprint. Since they produce a broader spectrum of light and not as much heat as the alternatives, they are often considered acceptable for low-to-medium light houseplants.
The main downside with LEDs is that they cost a lot of money compared to other options. Fortunately, though, as the technology improves, the price continues to drop.
How Do Plants Use Wavelengths?
The color of the light (or wavelengths of light) is exceptionally important for plants. There is still a surprising amount of debate about this, but plants use all of the wavelengths of visible light, including blue light, red light, green colors (although some growers will tell you differently), and more. There is even value to the non-visible light, such as the far-red and ultraviolet parts of the spectrum.
If we want to know the best light for plants, start by looking in the sky. The sun emits the entire spectrum of light. This is what we call full-spectrum light or direct sunlight. LEDs, specifically, can mimic this type of light, which is why we often credit them as having the proper spectrum of light for plants.
Most indoor plants flourish in full-spectrum bulbs (also called white light), which produce a balance of cool and warm light that simulates the sun. Seedlings, houseplants, culinary herbs, and a variety of other plants thrive with them.
The blue spectrum, in general, promotes the development of leaves, stems, and overall vegetative growth. Red wavelengths promote flower development, making it crucial for fruit-bearing plants. However, there is a wealth of information available on the unique advantages of red and blue lights. Some of it is also deceptive.
A good video on frequent misunderstandings about the color spectrum, notably red and blue light, may be found here:
What Do We Mean By Regular Light?
Most people would say that a regular light measures between (on average) 2,000 and 8,000 Kelvin, with lights on the lower end of the scale having a warm, yellowish-orange tint and on the higher end having a cool, almost bluish tint. Kelvin represents the color temperature of the light bulb.
This light is designed for two primary reasons – it’s used for people to see, and it’s used to make people feel a certain way about a room. A warm light, for instance, is said to make a space feel cozier and is sometimes recommended for living rooms.
Humans also deal in lumens, which is the measurement of light generated from a bulb. When purchasing bulbs for most home spaces, you typically need about 10 lumens per square foot. This means you can take your square footage and multiple it by 10-20. That said, a bathroom usually has more lighting, meaning you would want closer to 70-80 lumens per square foot.
Definition Of The Day: Foot Candles
A foot-candle is a British term for the measurement of lumens per square foot.
Here’s Where It Gets Tricky: PAR Vs. Lumens
While humans deal in things like Kelvin and lumens, plants experience light very differently. When measuring light for plants, we look at the following variables:
Photosynthetic active radiation (PAR)
PAR is the light at the wavelengths of 400 to 700, which is typically considered the light that drives photosynthesis.
Photosynthetic Photon Flux (PPF)
PPF refers to the measurement of PAR produced by a light source per second. This is expressed in μmol/second.
Photosynthetic Photon Flux Density (PPFD)
PPFD is the amount of PAR that actually reaches your plants. A light is scattering photons from its lights, so only a portion is actually getting to your plants’ leaves.
Can You Convert Lumens To Par?
Okay, so if humans deal in lumens and plants deal in PAR, surely there’s a way to convert them. Again, this is tricky. You won’t be able to convert lumens to PAR unless you have the spectral power distribution (SPD), which is a graph of the energy levels of your light – shown as wavelengths.
If you really want to do this, we recommend starting with this calculator from Waveform Lighting.
Do You Actually Need Complex Conversions?
We’re getting in the weeds a bit with this. In truth, most of us don’t need to understand the science between what humans and plants experience in terms of light.
Because of that, let’s go into the use case of when you can use a regular house light – what plants they work for – and how they compare to traditional grow lights.
Did You Know?
Did you know that, beyond lights, there are several factors to consider when growing plants indoors? When growing indoors, you need to also consider variables like humidity, growing mediums (LECA balls), fertilizer, watering needs, and more.
Which Regular Lights Work For Indoor Growing?
In terms of regular lights, you likely won’t be able to access the full spectrum of light in a single bulb. Blue light, though, is the primary color used for leaf and other foliage growth. So you want to use/purchase a cool light on the Kelvin spectrum – approximately 6,000 – 7,000 Kelvins. There are a surprising amount of houseplants that will do well under regular lights like these.
In terms of the type of bulb used, fluorescent lights and LEDs will be your best “regular light” options.
What Plants Grow Well Under Regular Light?
According to the University of Missouri Extension, low light plants need as few as 10-foot candles of light. For these low-light plants, a “single fluorescent tube such as a 2-foot 20-watt tube or a 4-foot 40-watt tube” provides enough light for the plants in this category.
Here are some plants that do exceptionally well under regular lights. These are also plants that are considered low-light plants.
- Philodendron Birkin
- Snake Plant
- Calathea (Prayer Plant)
- Spider Plant
- Chinese evergreen
- Peace lily
How Do I Know If My Plant Is Getting Enough Light?
The plant’s growth pattern might give you a decent idea if it’s getting enough light. No growth could suggest a lack of light, but it could also indicate other issues. Long internodes (stem length between leaves) or smaller-than-normal leaves, pale green stems and foliage, loss of leaves, and leaf yellowing could all be signs that your plants aren’t getting the light they need.
How Close Should My Regular Light Be To My Plants?
For low-light plants, you don’t usually need to worry about how close your lights are. Simple overhead lights should do fine, especially if they’re LEDs or cooler fluorescents. A plant that requires medium-to-bright light – such as the Monstera in the video above – will need a light much closer to the plants’ leaves.
Medium-to-high light plants may need a greater light intensity, so keep the bulbs within a foot of the leaf canopy.
You may need to adjust your light based on the needs of your plants. If it shows signs listed in the section above, you may need to bring the light closer or add additional lights. If you notice the edges of the leaves start to burn or turn black/brown, it may be a sign that your light is too close to the plant.
How Long Should I Have My Lights On My Plants?
A typical low-light plant needs about four hours of light exposure. But since you’re growing under a regular light, the lower light quality could mean that you need to extend the exposure. Start with at least six hours a day on low-light plants and see how your plants respond.
When it comes to regular lights vs. grow lights, it all depends on what you’re trying to accomplish. If you’re an entrepreneur growing food for the farmer’s market, regular lights do not make sense. But if you’re just trying to start seeds or grow low-light houseplants, everyday lights, specifically LEDs and fluorescents, do a fine job at keeping your plants alive and thriving. Like all things with gardening, the type of plant is a significant consideration, and you should expect to experiment to get the best results for your garden.
Are you using regular lights for your indoor plants? We want to know about it! Send an email and any pictures you have to [email protected]