Grow Light Spectrum Compared: Full-Spectrum & Broad-Spectrum Which Is The Best？

Both full-spectrum and broad-spectrum LED grow lights have the same seven visible colors as outdoor daylight. Either the full or broad light spectrum for plants will produce crops, but which ones should you use in your situation? 

A Full Spectrum vs. Broad Spectrum LED Comparison 

A full-spectrum grow light strip or lamp will appear similar to a broad-spectrum one in color. You may not be able to tell the difference between the two by looking at them with your eyes. That’s because all you see is a single light, usually bright white with a blue or yellow tint. 

The (Not So) Subtle Difference Between Full and Broad Spectrum Grow Lights

According to some full-spectrum LED grow light reviews, the broad spectrum does contain the full spectrum lighting for growing plants. However, broad LED lights may not have the ultraviolet rays (UV) from the sun that could benefit plants. 

Pros and Cons of Full Grow Light Spectrums 

LED grow light spectrums vary, so their effectiveness for indoor plant growing may also vary. The ideal full-spectrum bulb will measure at a temperature (CCT) of 6500K, the same rating as natural light. At this color temperature reading, your plants receive about as close to what they could get from sunlight to promote their natural development. 

The problem arises when working around full-spectrum grow lights for too long. If you stay close to them for longer than about 15-20 minutes at a time, they could burn your skin. That’s because they do emit some UV rays not good for humans in large doses. 

Full grow-light spectrums at the 6500K reading do provide an ideal color light wave range. Each light wave color contained within a full spectrum of light also appears at the right concentrations. 

Full-spectrum light is hard on the eyes when exposed to for long periods, however. In addition to UV light rays, it’s because of the amount of visible blue light in them.

Pros and Cons of Broad Grow Light Spectrums 

It’s tough to find unbiased sources about grow lights. Some sources suggest that plants could benefit from UV-A and UV-B rays. Unfortunately, these UV rays may not be present in some broad-spectrum grow lights. 

On the other hand, the absence of UV rays can prevent human skin and eye damage. For that reason, some growers prefer the broad spectrum, UV-free lighting systems. 

Should you use the full or broad grow-light spectrum?

Now you know some of the subtle differences between the full and broad grow-light spectrum. Now, it’s time to decide what’s right for the plants you want to grow. 

For instance, some types of CBD derived from cannabis do better with broad-spectrum grow lamps. Other strains of marijuana may grow better using the full spectrum strip lights. 

Your choice of LED growth light spectrum also depends on the variety or sameness of your crops. For instance, are you going to grow only one type of tomato, or do you want to produce a mixture of red vine, Roma and grape or sandwich tomatoes? 

Factors to Consider When Choosing Full Vs Broad Spectrum Lights

It’s not an easy decision, and you have other factors to consider too. For instance, some lights perform better in smaller spaces, but others illuminate larger areas. 

You also may have specific growing objectives, such as producing as much fruit in a six-week period as you can. Otherwise, maybe you don’t mind if it takes your plants a little bit longer to develop as long as it increases the fullness of the plant leaves, stems, flowers, etc. 

Just about any type of light can have some growing benefit to plants. Even standard household bulbs work in a pinch, and so do fluorescent or HPS (high-pressure sodium) bulbs. However, nothing seems to beat the performance of full spectrum LED grow lights for indoor plants, but you have to ask the right questions to maximize your interior gardening experience. 

Plant Light Spectrum Questions to Ask 

Fine-tuning your plant light spectrum is possible. For instance, the TFDG Series toplights have multiple dimming modes and come in different wattages. However, you also need to ask yourself general questions about planting in addition to choosing the ideal plant light spectrum. 

How much are you willing to spend on power? 

Make sure you “count the costs” of preparing for your ideal plant light spectrum environment. You can use a simple calculator to determine how many kilowatts of power you’d use. 

Of course, this depends on how much your local utility company charges. Look at your bill for the amount per kilowatt-hour (kWh). Otherwise, contact your power provider and ask them. 

The cost of power to grow your plants also is determined by how many hours per day you run your lights. Figure on the high end of 12-18 hours of “daylight” and a lower light setting for nighttime that mimics the moon. 

Of course, you will want to add the cost of all the grow lights you install. You can determine this by their individual capacities, such as the square footage of illumination they would provide. For instance, some lights may provide a spotlight over about four feet by four feet area. 

Larger commercial lights might take up an entire 8 feet by 10 inches of space –or more. It depends on the system you install. 

Do you have enough space for your plants to grow? 

At first, you may not need as much growing space because younger plants don’t need much room. However, you will need to prepare for the future, so keep your seedlings about 18-24 inches apart from one another. 

If you’re planting seeds instead of starter plants (seedlings), you could place them about 6-12 inches from one another. If you do this, make sure you transplant them as your crop stems and leaves start to crowd each other. This may require you to also expand your growing area. 

How many plants do you want to produce?

If you’re just growing a few plants for yourself, you can probably get away with a seedling light. That will at least jumpstart your production, and the SYM series would work well for home LED grow light spectrum environments. 

In fact, we recommend conducting light spectrum for plant growth tests. Set up these experiments little by little at your house first.

For instance, you can designate a corner in a spare bedroom or near an attic window for now. Find out how well that works for you before you invest in large-scale, commercial full-spectrum growing lights. 

What are your primary growing objectives?

Some growers want to maximize their total yield, growing as many plants as they can as fast as possible. However, you may not always have the richest leaves or the sweetest fruit when performing your initial “mass growing” tests. 

You may also want to figure out how you can best activate the photosynthesis process. This usually requires blue light. Otherwise, you will want the red light used for sprouting, vegetative or flowering stages. 

How much “natural” light do you have?

Growing in a room with windows in it could cut down on the amount of full spectrum grow lighting you need. However, you may want to experiment with full-spectrum plant lights at different levels.

Also, test your full spectrum lights for plants both in an environment that takes in sunlight and in a room that has no windows. 

Additional Questions and Answers

Why should you use “white” (broad or full spectrum) lights? 

When starting out, you may not produce as high of an indoor gardening profit as an experienced grower. Installing either a broad or full spectrum growth light setup will help you cut down on the costs of production. It allows you to access all visible light waves, including the red, blue and green often used for plants. 

What are the most useful light waves in broad or full light spectrums? 

All the visible light waves, which are red, orange, yellow, green, blue, indigo and violet are useful. However, the red light waves seem to provide a better quality plant.

The blue light waves help produce the chlorophyll that helps plants convert light into food. The green light could be considered more of a “neutral” wave, being in the middle of the full spectrum. 

The green light, which you can switch on within some growing light setups, works well during the plant maintenance periods. It’s usually easier on the eyes than either the warmer (red, orange and yellow) and cooler (blue, indigo and violet) waves. 

So is full-spectrum or broad light spectrum better for plants? 

The necessity of UV lights provided by full-spectrum lighting leaves much to be explored. It wouldn’t hurt most plants in moderation. Still, you have safety issues to consider. 

If you don’t feel right about producing UV rays near pets or children, use broad-spectrum lights. If you’re setting up a large commercial growing environment, you may want to experiment growing with both broad and full spectrum lights. 

The intensity of your lights may matter more than whether they contain UV rays. For instance, you may want to set up less bright lamps during the initial growing phases. This can help you use less water. 

On the other hand, a brighter light will “jumpstart” your plant growth. It also will cause faster, more increased flowering come time to produce vegetables and fruit.