This is the beginning of a series of articles covering each type of light commonly used to grow indoor plants. Fluorescent grow lights for indoor plants are not my first pick but they definitely have their place in the “growing” world. Their low cost and energy consumption are huge pluses.
Are All Fluorescent Grow Lights for Indoor Plants Created Equal?
The quick answer is no but more on that in a second. First of all, however, I would like to say a quick word on incandescent bulbs: don’t use them. Incandescents do not have anywhere near the light spectrum of a fluorescent and throw way too much heat to be of any use to plants. By the time the plant gets close enough to them to get adequate light, the heat will desiccate and burn them up.
Most large-scale and commercial operations use LED lights because they last longer and emit more light. Fluorescent bulbs are also more fragile, meaning a farmer can incur additional labor costs to maintain them, and that may not be worth the time or money. However, the small-scale or hobby farmer may find fluorescent lights to be an economical choice, especially for low-light plants or plants at a low-light stage of development.
How Fluorescent Lights and What to Look For
All fluorescent lights work in a similar fashion:
- An electric current heats up gas inside the tube, which emits ultraviolet light.
- Meanwhile, a phosphorus coating inside the tube turns that ultraviolet light to visible light.
- A ballast on the back converts the incoming electrical current into a usable form.
You’ll see several numbers on a fluorescent light that give you information about how it works, and help you avoid lights that are too dim.
Tubular lights have a “T” rating that tells you the diameter of the tube. T12 lights have that designation because they have a diameter of 12/8 of an inch or 1.5 inches. These tubes were commonly used in indoor lighting applications, but they’re just not very bright, even with a coating to make them full-spectrum.
T5 lights are narrower than T12s, with a diameter of 5/8 of an inch. Look for a T5 bulb with an additional “HO” rating, which stands for “high output.” That means the ballast has been adjusted to make them even brighter—and for growing purposes, more efficient.
When buying a full-spectrum grow light, you also need to look at the Kelvin rating, which indicates how warm the light is. Fluorescent lights, in general, tend to be bluer but look for a light ranging from 5,600–6,400 Kelvin, which will be indicated on the bulb. On the lower end of that spectrum, the bluer light will give you stockier growth, while the higher rating is great for any kind of vegetation.
Fluorescent lights will also come with a wattage rating to tell you how much electricity the bulb uses, usually 54 watts.
What Colour Lights do Plants Grow Best In?
Plants need the full spectrum of light of they do best with blue and red, depending on the stage of growth they are in. The ideal ration is 5:1 red to blue but don’t forget that red light without the blue light is actually worse than red without the blue.
Blue light is the most important during vegetative growth. Blue is the most important light for plant growth, because it is readily absorbed by chlorophyll and converted into energy through photosynthesis. That said, blue light on its own is not nearly as effective as blue combined with red. And you want far more red than blue light.
Red is the second most important wavelength of light for plants. On its own, red is actually not all that effective, but when combined with blue, it becomes incredibly important. In fact, you want far more red than you do blue, especially during the flowering stages of growth. Adding red light leads to stronger growth with more leaves during vegging and far better fruit and bloom production during flowering. Not only do you get higher yields, but also higher quality yields.
This is one reason why LED lights are much better than fluorescents unless you are only growing leafy green vegetables.
Advantages of Fluorescent Grow Lights
- Very low heat emission, making them safe to place close to plants
- High energy efficiency
- Lower initial costs compared to other types of lighting systems
- Can be placed in different positions to ensure all parts of the plant have adequate lighting
- It is the best type of light for seedlings and clones, due to low radiated heat
- Can accelerate plant growth when used as under-lighting for outdoor plants or in greenhouses
- Fluorescent lights produce the right intensity of light for healthy stems and foliage
- They can produce sufficient energy for flowering (though this is not their strength)
- To reduce energy consumption, the fluorescent light can be used to supplement other types of grow lights
- Fluorescent lights are very simple to use
- They have a natural light spectrum lying between the red and blue wavelengths, which ensures healthy plant growth and productivity
- They are the best for most house plants due to the full daylight spectrum, similar to the sun
- Produced in a wide range of sizes and shapes, which means they can be placed in varying positions, including in close proximity to plants, which adds to the convenience of use
- Come in a range of light colors (warm white, cool white, daylight, etc.)
- Can be hung vertically and horizontally
- Most have a life span of tens of thousands of hours of service
- They have no-glare light which is friendly on the eyes
- Some of the latest fluorescent lights can give more than 90% of the solar spectrum
- Fluorescent light tubes fit easily into reflectors, so you can get set up very quickly and easily
For example, if you have a system such as one pictured here, fluorescents would be perfect to fit between and above the levels.
Disadvantages of Fluorescent Lights
The main disadvantage of any fluorescent grow light is its usefulness during flowering. They can certainly be used for flowering, but they just don’t have the power to give you the same results as an HPS bulb or a good LED light.
You can improve results by swapping the bulbs out for warmer ones with a temperature of 2700 to 3500K. But even then, T5 fluorescent lights are not ideal for flowering. That said, they cost less initially, use much less power and emit less heat than the alternatives. Some people are happy to sacrifice a bit of yield for those advantages.
The other disadvantage is that, for a large garden, electricity costs and heat output start to add up with fluorescent lighting. This is where LED grow lights start to make more sense, even if you’re only vegging, but especially if you need lighting for all grow cycles.
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Hydrofarm AgroBrite T5 Fluorescent Grow Light
These grow lights are priced much lower than competitors of similar quality and deliver far more than any similarly priced lights. They are available in 7 different sizes, from a 2 foot, 2 bulb unit to a 4 foot, 12 bulb unit. No matter the size of your garden, there’s an AgroBrite fixture to cover it.
T5 fluorescent grow lights emit much less heat and use far less electricity than metal-halide bulbs and they cost less initially, too. They don’t beat LED lighting in terms of heat or power consumption, but they are obviously far cheaper.
Their main disadvantage is that they are not good at flowering. If you are looking for a flowering light, you are better of with LED grow lights or with metal-halide lights but if you need a light for vegetative growth, cloning or for your seedlings, the Agrobrite fixtures are perfect.
- Uses 48 to 648 watts — wattage depends on the number of bulbs and their length; see table below
- 4000 to 60,000 lumens — also depends on the number of bulbs and their length; see table below
- Includes 6400K T5 bulbs — ideal for vegging stage of growth
- Can hang 3 ways — overhead, vertical or horizontal
- Powder coated steel housing — sturdy and sleek
- High performance faceted specular aluminum — better light distribution
- Daisy chainable — run multiple fixtures from one outlet
- Multiple on/off switches on larger fixtures — control the lumen output by turning off bulbs when less light is needed and save money
Hydrofarm’s Agrobrite series of T5 fixtures come with 6400K spectrum T5 grow bulbs, making them perfect for seeding and cloning. They are also excellent at vegetative growth.
You can see these lights on Amazon in all of their different configurations HERE.
The Agrobrite line of T5 fluorescent lights from Hydrofarm are the only T5 fixtures I’ve shown on this blog for a reason. They are easily the best value on the market AND they come with a 5 year warranty, which is unheard of in this price range.
Yes, there are better lights, but they cost a lot more. And obviously, there are cheaper lights, but they just don’t perform well enough to give you good, strong plant growth. And again, none will give you a 5 year warranty.