As indoor farming gained popularity, artificial lights got better at replicating the sun. Now, we have plenty of choices for growing plants without any sunlight indoors. These fixtures are referred to as grow lights.

7 Steps for Picking the Best Grow Light
7 Steps for Picking the Best Grow Light

Leah Soto | Pure Greens LLC

We all know plants use sunlight to grow.

That’s one reason we usually grow plants outside.

But as indoor farming gained popularity, artificial lights got better at replicating the sun.

Now, we have plenty of choices for growing plants without any sunlight indoors. These fixtures are referred to as grow lights.

Choosing a grow light might be overwhelming, but it doesn’t have to be.

Follow these 7 steps for a smooth process to find your perfect grow light.


Choose your crops

Planning the crops you’re going to grow ahead of time will make your decisions a lot easier.

You need to know what type of and how much crops you’ll be growing in order to know how much and what lighting you’ll need.

The list doesn’t have to be too detailed.

But crop type will influence the intensity, spectrum, coverage, and type of bulb you need for your farm.

For example, if you plan on only growing microgreens, your lighting needs will be very different from someone growing flowers.

This is because plants need different lighting at different stages of growth.



Having a budget in mind before you start shopping will also make the process easier.

This way, you can eliminate some options right away.

When planning your budget, consider your desired energy costs and the amount of light needed.

The wattage of the bulbs you choose will influence how much you spend on energy.

If you have a small operation, where you’re only growing a few plants, this might not be too big of a concern.

But for commercial scale farmers, you’ll want to search for high efficiency lights.

Remember that these lights will be on for at least 12 hours per day. That’s quite a bit of energy!

Plus, the type of light you choose will influence the cash you spend on it.

You may be searching for an entire fixture, but you may also only purchase bulbs, which is cheaper.

You’ll also have to factor in whether you plan on only buying one light or multiple.

We’ll get more into bulbs later but note that different bulbs are also priced differently.


Choose Your Bulb Type

The three most common bulb types for grow lights are fluorescent, LEDs, and HIDs.

Incandescent bulbs aren’t on the list because they give off too much heat, which can burn foliage.

Fluorescent bulbs are the most affordable choice.

They’re best for growing just one or two plants.

However, they’re not very efficient and have a shorter shelf life.

In fact, LEDs use half of the electricity and last five times longer than fluorescents. 

LEDs have the best spectrum coverage, emit little heat, and are highly efficient. LEDs also come in an high intensity option that is suited best for sun-loving crops, like rosemary.

They’re a solid choice for almost every operation.

But they are more expensive than fluorescents.

HID lights are most commonly found in large-scale commercial growing.

They need special fixtures, but they can be installed just about anywhere.

They’re extremely bright and replicate sunlight the best.

However, they’re the most expensive option and emit a lot of heat.


Decide on Spectrum

Light comes in different colors, referred to as the spectrum.

Most plants use light from the blue and red ends of the spectrum, with a little bit of yellow and green thrown in.

Blue light is used mostly for vegetative stages to establish leaves and roots.

Meanwhile, red light is used for producing flowers and fruit.

Grow lights come in two types: Targeted spectrum and full spectrum.

Targeted spectrum lights emit a specific color, like red or blue. As a result, they’re best for only specific crops or specific growth stages.

Full spectrum bulbs imitate sunlight more naturally and cover all stages of growth.

Plus, because full spectrum bulbs emit white light, it’s easier for us humans to see.

However, it’s important to note that some targeted spectrum lights come with a switch that allows them to change color, making them useable for different stages.

To go back to our example, if you’re only growing microgreens, you don’t need full-spectrum light as the plants need more blue light to grow.


Look at Intensity

Intensity refers to how much light actually reaches the plants from the fixture.

Intensity is important because you’ll want to be sure you can provide the right amount of light for the number of plants you have at each stage of their growth cycles.

The higher the intensity of a grow light, the farther you can place it from the plants to minimize heat and light burns.

To decide if the intensity is right for your desired coverage area, consult the manufacturer.

The manufacturer will provide an estimated coverage area. However, if you want the best results possible, you’ll need to go a bit further.

First, find the photosynthetic photon flux density (PPFD) measurement of the light.

This measurement is the average density of the total light output of the fixture. It indicates how intense the light is within a set area.

Keep in mind that light intensity is higher at a center point and gradually lessens as you move away from that spot.

That’s why you’ll next want to consult the manufacturer’s photosynthetic active radiation (PAR) chart.

The PAR chart shows the distribution of the light’s PPFD in an area.

The density will be most intense in the middle, less intense on the edges, and least intense in the corners.

Ideally, you want a light that has a low PPFD with an even distribution, as shown in the PAR chart. This will influence the number of grow lights you’ll want for your grow space.

Vertical farming produce


Figure out Needed Coverage

Once you’ve narrowed down your list of potential candidates, you should determine how many you’ll need to purchase.

First, measure your grow space.

The general recommendation is 20 to 40 watts of coverage per square foot.

Look at the wattage of one of your potential grow lights and divide that number by 20. That will give you the lowest area of square feet that bulb will cover.

Divide the wattage by 40 for the highest area it’ll cover.

For example, a 1,000-watt bulb will light between 25 and 50 square feet of your grow space.

Additionally, be sure to match up the results of the PAR chart with your grow space for more precise coverage.

For example, a PAR chart may show fairly uniform density until it reaches a 16-square-foot area.

To light an 80-square-foot grow space with that bulb you’d need 5 of them.

In other words, the total grow space area divided by the bulb’s coverage area.

Unless you’re truly only growing a few plants, you’ll want to buy multiple lights rather than one large one.

This way you can ensure full coverage, with even intensity distribution.


Consider Height and Mobility

Before committing, consider how far away from your plants your grow light(s) will be and how mobile you want it.

Many grow lights are adjustable in order to keep a consistent distance from the plants as they grow.

In other words, the light will sit lower when the plants are sprouts. Then, it’s moved higher as the plants mature.

When choosing a grow light, you’ll want to make sure it has this function installed already, or that it won’t be too difficult to adjust manually.

Especially if you’re growing taller crops.

The hotter the bulb gets, the farther you want to keep it from your plants.

If this interferes with your desired intensity and wattage at all, you may need to choose a different light.

Remember, at the end of the day, there’s no universally right or wrong choice when it comes to grow lights.

Use these 7 steps to make the process of finding the perfect grow light for your grow space easier!

If you’re still looking for a space for your indoor farm, check out our Pure Greens Container Farms.

They come turnkey ready, so you won’t even have to pick out your own lights!


The content & opinions in this article are the author’s and do not necessarily represent the views of AgriTechTomorrow

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