T5 Fluorescent Vs LED Grow Lights (The Lettuce Test)

LEDs are clearly better than fluorescent grow lights, right?

Well, not always. It really depends on the LED in question.

And on what you are growing.

For small grows, you’re often better off just using a fluorescent light.

This experiment proves that.

It also shows the ineffectiveness of using all-blue light for vegging.

Sure, plants need more blue light during vegging than flowering, but they still need the other colors, too.

The ideal vegging light has more blue light, but not only blue light. This is why the market has shifted to full-spectrum white LEDs.

Keep reading for all the details about the test and for a breakdown of the results. We’ll go into detail about what it means in terms of which lights, LED vs fluorescent grow lights, are most effective.

 

Fluorescent Vs LED Grow Lights: The Lettuce Test

Let’s get right to it and take a look at what this little experiment was all about. We’ll go over the setup and premise first, then cover the results and the conclusion.

 

The Experiment

This guy grew a head of lettuce (he used seedlings first, but discarded that experiment) under three different lights. One light was a T5 fluorescent grow light, the other a 15 watt all-blue LED (for vegging) and the third a 45 watt red and blue LED.

He actually tried a different fixture at first, but it didn’t draw the claimed wattage. Neither did the second, but he went with 45 watts to ensure it was powerful enough, even if it didn’t deliver as advertised.

This just shows you how many bad manufacturers are selling low-cost LEDs on Amazon. You really have to be careful, especially with the cheaper grow lights.

In terms of cost, all option were fairly close when calculated on a cost per square inch basis, though the LEDs would cost less to run long-term. How about the results?

Knowing what I know about grow lights, the results did not surprise me at all. I expected him to end up with one nice head of lettuce, one decent head of lettuce and one sad little shrub. And he did.

Can you guess which light was responsible for which head of lettuce?

Let’s find out.

 

Results

The experiment went exactly as I would have expected. The T5 fixture with its full-spectrum white light did the best job, the red an blue LED did the second best job and the all blue LED did virtually nothing.

• The T5 used about 48 watts per plant and resulted in the most growth by far.
• The 45 watt red and blue LED used about 29 watts and did well, but not as well as the fluorescent fixture.
• The 15 watt blue LED did virtually nothing.

Even in his original experiment with the seedlings, the all blue light proved to be basically useless. Everyone always says that plants need blue light when vegging, but they don’t ONLY need blue light.

They still want other colors as well, especially red. They just absorb more blue light during vegging than they do during flowering.

 

Conclusion

These results verify what I’ve always said.

Don’t bother with these low wattage LED fixtures, unless you’re using them as supplemental lighting. And in this case, they were only being asked to veg. If you were growing tomatoes indoors using artificial grow lights, or any other plant that flowers, you’d need even more power.

Also, don’t bother with lights that have only one or two different colors of diodes. Wondering why your grow lights are purple and make your plants look unnatural?

Because they only have red and blue diodes.

In the past, grow light manufacturers told us that plants need red and blue light to grow properly. Yes, they get all colors from the sun, but they only use red and blue.

Of course, their lights had only red and blue diodes. White diodes were not as easy to produce.

That said there is some truth to the red and blue theory. Plants do use those colors more than others. But they do not use only those colors, as mentioned.

These days, we know that full-spectrum white light grows and flowers plants much better. Especially if it is supplemented with some additional deep red light.

And that is the spectrum today’s best LED grow lights give you. If you get an LED grow light, definitely get one with mostly white diodes. Your plants, and your eyes, will be much happier.

You also have to consider the power of the LED light.

If you want to replace a fluorescent fixture with LED light, you need to get an LED fixture that draws at least 30 watts per square foot. Anything less just won’t cut it on its own.

Read about lumens versus PAR and the science behind LED grow lights to understand why.

Ideally, you want to get something even more powerful than that, if you are really trying to take advantage of the cost and heat savings that LED lights can provide over fluorescent grow lights and HID lighting systems.

But really, for small gardens like the one in the video, you’re often best off using a fluorescent light, unless you can afford to spend a few hundred dollars on a quality LED fixture.

If you go cheap, you’ll end up being one of those people that asks themselves: do LED grow lights work at all?

But if you spend a bit more money to get a quality LED grow light, and especially if you are growing more than a single small plant, then LED has many advantages over fluorescent lights.

 

Advantages Of LED Grow Lights

LED fixtures are better in most cases, as you will see from the advantages.

• Far more efficient, in terms of output per watt consumed
• Emit far less heat for the output they produce
• Spectrum can be anything you want, meaning quality LED fixtures give your plants the perfect light spectrum
• You can dim the best LED grow lights, so you can use less power during vegging and increase intensity during flowering when plants need more light
• Cheaper for larger fixtures

Basically, if you have a very small garden of plants that do not flower, then fluorescent may be the better option. Otherwise, you are definitely much better off with am LED grow light. But only if you get a quality full-spectrum LED grow light.

 

Advantages Of Fluorescent Grow Lights

Fluorescent lights have far fewer advantages and they really only come into play when you have a very small garden. As for T5 vs T8 grow lights, they both have the same advantages and disadvantages, but T5 is the newer technology and thus slightly more efficient.

• Much cheaper, but only for smaller amounts of light
• Produce less heat, but only for small lights

Basically, fluorescent fixtures are a good idea if you only need a small amount of output. For example, if you have a small herb garden or other non-flowering plant (like lettuce) and other leafy vegetables suitable for indoor growing. Or if you are seeding marijuana.

If you’re not sure which type of fluorescent lights to get, check out this post. If you already have a fixture and just need bulbs, this post has what you need.

Whichever light you get, you want to be able to move it up and down as the plants grow. This means either a ratchet type hanger or an adjustable grow light stand.

 

T5 Grow Lights Vs LED: Final Thoughts

T5 fluorescent grow lights are excellent at vegging small gardens. If you have a small herb garden, a few heads of lettuce, etc., they have a number of advantages over LED light. But mainly, they are cheaper.

However, if you have a larger garden, or if you have plants that flower like cannabis, then fluorescent light just are not powerful enough. You would need so many of them that you end up spending far more to buy, and to operate, them than you would on an equivalent LED grow light fixture.

In short, when it comes to fluorescent vs LED grow lights, LED lights are always a better choice, but fluorescent has enough advantages for certain situations to make them a better choice for some people. Outside of those situations, LED grow lights are always the much better option.