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What Kind Of Fluorescent Lights To Grow Plants (Including Weed)?

Last updated October 9, 2020 By Steven 20 Comments

The short answer is: any type of fluorescent light will help any type of plant grow, whether it is cannabis or lettuce or orchids.

But it’s not quite so simple.

While you can use any type of tube or bulb and see results, you want to provide the kind of light your plants want most.

That’s how you get the best results.

So what type of light do your plants need?

That depends on a few things.

  1. Are they plants that flower (like marijuana) or ones that don’t?
  2. If they flower, they need different type of light depending on their current stage of growth, so you’ll need to take that into account
  3. Are they already getting some natural light or will they be growing under artificial light only?

Fluorescent Growing Lights: CFL or T5 Tubes?

Before we get into the specifics on the types of bulbs or tubes, let’s first decide whether we want to go with fluorescent tube lighting or with compact fluorescent bulbs.

The answer is simple.

If you’ve got a very small garden, CFL bulbs (pictured at the beginning of the article) make the most sense.

If your garden is large enough to warrant a larger T5 tube fixture, go with that. And perhaps supplement the light with a few CFLs, especially for plants with high light requirements, like weed.

As for which bulbs to get, it doesn’t matter with CFL bulbs. You can just get any standard bulb from your local Home Depot or Walmart or order online (if you’re unsure about the correct color temperature, I cover that below).

There is no need to get a specialized (and overpriced) grow bulb. They’re basically the same thing. It’s just a way to get more of your money.

For T5 fixtures, I recommend the Agrobrite line from Hydrofarm (pictured above). We reviewed them here, but the quick summary is that they cost about the same as most no-name fixtures from China, but work far, far better.

You can use regular fluorescent bulbs from any local store, but for larger fixtures like this, it make more sense to buy from a company specializing in horticultural lighting. And Hydrofarm is the biggest name there is.

Now, let’s take the first question from above and tackle plants that flower and those that don’t separately.

The second and third questions will be answered naturally as we go along.

What Fluorescent Bulbs for Growing Flowering Plants (Marijuana, tomatoes, etc)?

Flowering plants, like cannabis, need more and different light than non-flowering plants. But only during the latter stages of growth.

In the beginning, flowering plants need the same light as non-flowering plants. When they are seedlings and when they are growing (vegging), they need light that contains more blue than at other times. This is also often referred to as ‘cold light’. It is the kind of light our sun gives off naturally during daylight hours.

When the plants have grown enough to begin fruiting or flowering, they need more light than before and they prefer a warmer light, i.e. light that contains more red.

So how can we give them the light they need with fluorescent bulbs?

By using bulbs with varying color temperatures.

During the seeding and vegging stages, we want to use bulbs labeled ‘cool white’ or ‘daylight’. They will have a color temperature (usually indicated on the package) in the range of 6000K to 6500K.

During flowering, ‘warm white’ bulbs are ideal, with a color temperature of 2700K to 3500K.

It might seem like a hassle to change bulbs when it is time to go from vegging to flowering, but it’s really only a big deal if you have a very large garden with a lot of lights.

And if that is the case, you should not be using fluorescent lighting anyway, as the disadvantages outweigh the advantages once a grow gets too large.

However, if you just don’t want to bother with having to change the bulbs, you can get lights with a color temperature in the middle, somewhere around 5000K.

These bulbs will work fine for all stages of growth. In reality, any bulb will work for any stage, but using bulbs that provide the right kind of light yields much better results.

In most cases, you will want to supplement the light you use during vegging with some additional bulbs. Personally, I just hang a few CFL bulbs (warm light) here and there to add some more output and really stimulate flower and bud production. If you are unsure how many CFLs you need, this article will help.

What Kind of Fluorescent Bulbs for Plants that Don’t Flower?

If you are growing plants that don’t flower, like cacti, herbs, lettuce, etc. then you do not need to worry about providing warmer light during flowering.

You just need to get some ‘cool white’ or ‘daylight’ bulbs and use them all the time. No need to switch lights. This article reviews the best T5 bulbs for vegging.

Best Fluorescent Grow Lights

Let’s quickly summarize which fluorescent lamps are best, whether you are interested in getting CFLs or T5 lights.

As mentioned above, when it comes to compact fluorescent lamps, I would not worry about getting a dedicated grow bulb. They cost a lot more, but are basically the same as a regular CFL bulb.

As for which brands are best, follow the links provided above to see my recommended bulbs for each color temperature. I like those lamps, because they offer the best value for money.

Amazon will also show you other options, so you can easily see some alternatives and do a quick comparison for yourself, if you don’t like my recommendations.

When it comes to T5 lights, I always recommend the AgroBrite fixtures from Hydrofarm. Check out my AgroBrite review to see why I prefer these lights.

If they don’t have a fixture in the size you need, or if you only need bulbs, this post reviews and compares the top T5 tubes on the market.

Update: while I still love fluorescent light for growing cannabis and other plants, these days I tend to recommend T5 LED lights instead. They are basically exactly the same as a T5 fluorescent light, but they run cooler and use less power. They also last much longer.

They do cost more, but end up paying for themselves within a year, since they cost less to run and you don’t have to replace them for many years.

The short answer: any type of fluorescent light helps plants grow. But it's not that simple. There are a few things you need to be aware of to avoid…

Grow Light Breakdown: Heat, Cost & Yields

For the many growers who are unable to cultivate cannabis outside in the free abundant sunshine, grow lights are necessary to successfully grow cannabis indoors. Grow lights take the place of the sun, and power the growth of your plants and their buds. Light is like “food” for your plants, so without a lot of bright light, even a healthy cannabis plant won’t produce much bud at all.

More Light = Bigger Yields!
(up to a point, it is possible to give your plant too much light!)

3 Main Classes of Marijuana Grow Lights

There are lots of options for grow lights that work well for growing cannabis indoors but in the end they boil down to 3 major types:

  • (LEDs come in a huge variety of sizes and form factors. There aren’t really any “standard” types yet, though some lamps get better results than others.)

Note: Some growers may have heard of “Induction” grow lights, which are pretty rare these days but still pop up from time to time. There are two types: “Magnetic Induction” grow lights do okay for growing cannabis but they’re pretty much glorified fluorescent lights. “Plasma Induction” grow lights actually perform pretty poorly at growing cannabis.

Some types of induction lights are well suited to stadium lighting but honestly they just aren’t that great for growing cannabis and they come with huge price tags. Even a lot of LEDs are cheaper and you’ll get better results with them. You can learn more about induction grow lights here.

Note 2: Incandescent light bulbs (old fashioned light bulbs) are NOT suitable for growing marijuana!

Compare the Pros and Cons of Each Grow Light

1.) Fluorescent Grow Lights

Fluorescent grow lights come in many different shapes and sizes, from twisty bulbs to long tubes. Fluorescents are popular because they make efficient and pleasant lighting for humans, and also work great for herb gardens and other types of low-key indoor gardening without using a lot of electricity.

CFL Grow Lights

CFL grow lights are the twisty-looking bulbs you can find anywhere you normally buy light bulbs. They produce a great spectrum for growing cannabis and can be used in tiny spaces where no other grow light would fit such as the inside of a cabinet.

Keeping CFLs close results in the best yields and growth

T5 Grow Lights

T5 grow lights are one of the most easily available types of grow lights and are used to grow many different types of plants. As a result, they’re available in many garden and home improvement stores.

T5s are much bigger/wider than CFLs and usually come as part of a panel, but they can still be kept mere inches away from your plants without worrying about burning them.

These cannabis plants are thriving under T5 grow lights

Pros of Fluorescents

  • Cheap to buy
  • They don’t use a lot of electricity or make a lot of heat unless you have a lot of them packed together in a small space
  • Great light spectrum for growing cannabis
  • Since lights can safely be kept just a few inches away from plants, they’re a good choice for short spaces
  • One of the best lights for clones, seedlings and young plants. Big lights must be kept far away from young plants to avoid burning them, which ends up wasting a lot of light and energy. By using smaller lights like fluorescents while plants are still short, you can save quite a bit of money on electricity during those first few weeks compared to using a high-powered grow light.

Cannabis plants under a T5 grow light – when plants are trained (like these ones in a Scrog setup) you can get pretty decent yields from fluorescents.

Cons of Fluorescents

  • Fluorescent grow lights get smaller yields per watt than the other types of grow lights if you use them in the flowering stage while buds are forming. With fluorescents you can expect about 0.25 grams of buds for every watt of electricity (using the true watts out the wall, not any type of “equivalent” watts), while LEDs and HPS get 2-4 times as much yield per watt of electricity.
  • The light from a fluorescent lamp doesn’t penetrate far down into the plant so they are best suited to plants that have been trained to grow short and flat; they aren’t powerful enough to support tall plants in the flowering stage.

Fluorescents are a great choice for clones, young plants, supplemental lighting and can save you money on electricity in the vegetative stage compared to using high power lights when plants are too young to use it all anyway. They can also be used to flower plants in spaces that are shorter than what’s possible with other grow lights (aka ‘stealth growing’).

That being said, when it comes to the flowering/budding stage, if you can fit a bigger light you will get significantly better yields/watt by using an HID or LED grow light!

2.) High Intensity Discharge (HID) Grow Lights

HID grow lights are much more efficient than fluorescent lights and are powered by large, oddly-shaped bulbs. They are usually screwed into a reflector or hood to reflect more light down onto the plants. HIDs are great at growing cannabis, but they also get very hot and are usually hooked up to an exhaust to help vent out heat.

Full tutorial on MH & HPS grow lights
(most common grow light combination for cannabis)

Full tutorial on CMH / LEC grow lights
(LEC stands for “Light Emitting Ceramic” and is a type of Metal Halide bulb that is built with ceramic like an HPS – basically it’s sort of like a blend between MH and HPS bulbs)

Metal Halide (MH) Grow Lights

Metal Halide grow lights are generally used for the vegetative stage because they produce a bluish light that vegetative plants love, though this type of light can also be used all the way to harvest.

The light from a Metal Halide appears a little bluish, and is well suited to growing cannabis plants in the vegetative stage

High Pressure Sodium (HPS) Grow Lights

High Pressure Sodium grow lights are often used during the flowering stage because they are very efficient and their yellow light stimulates bud production. HPS grow lights in the flowering stage get better yields per watt of electricity than any other type of grow light available today, which is a big part of why they are so popular.

The light from an HPS appears yellow, and is great for flowering plants because the light spectrum stimulates bud production

Ceramic Metal Halide (CMH) & Light Emitting Ceramic (LEC) Grow Lights

These are actually just two names for the same thing. This type of metal halide bulb uses ceramic as part of the lamp just like an HPS. As a result, CMH bulbs are more efficient than regular MH lights (though still not as efficient as HPS bulbs).

“LEC” and “CMH” both refer to Ceramic Metal Halide grow lights, which is a type of HID light that is a bit more efficient than a regular Metal Halide light

Pros and Cons of HID Grow Lights

  • HIDs are the most efficient type of grow light (gets the highest yields/watt).
  • Of all the HIDs, HPS grow lights are the most efficient and the best for the flowering stage. When using HPS grow lights in the flowering stage, you can expect about 0.5-1 gram/watt if all goes well.
  • HID lights are simple to use because they can be hung the right distance from the plants with no guesswork on your part (unlike LEDs), and no need to adjust the lights all the time (like fluorescents).
  • HID bulbs get really hot and generate a lot of heat. Because of the concentrated heat production, you will almost always want to put the bulb in a hood and also provide some sort of cooling to prevent heat from beaming down onto your plants and driving up the ambient temperature of your tent/grow room. This is especially important for the bigger lights with power above 250W.
  • Additional setup – As a result of the heat mentioned above, most growers use an exhaust fan with ducting to vent out heat. Unfortunately, the prospect of having to deal with the fan and ducting scares off many growers from HID lighting.
  • More parts – HID lighting means a few more parts than other types of lighting. Fluorescents are just the bulb and a fixture and most LEDs are just the light itself. But most HID setups have at least a bulb, fixture, an external ballast and an extra cable if you don’t count the exhaust systems parts, too.

Example of MH/HPS Setups That Yield 1-5 Ounces/Month

  • 1-2 oz per month
  • Electricity: $69/month (including electricity for fans)
  • Initial Setup Cost: $605.00
  • 1.5 – 3.5 oz per month
  • Electricity: $96/month (including electricity for fans)
  • Initial Setup Cost: $744.00
  • 2.5 – 5 oz per month
  • Electricity: $128/month (including electricity for fans)
  • Initial Setup Cost: $780.00

There is a larger size MH/HPS grow light available (1000W), but at that size it starts going outside the scope of a “hobbyist” grower as far as ease and yields. In addition to needing a lot of extra cooling which costs electricity, a 1000W HPS grow light is less efficient compared to a 600W grow light (as far as how much light is put out for electricity used). I think most hobbyist growers would be happier with a 600W, or even two 600W lights, over a 1000W 🙂

HIDs are very well suited to growing cannabis and very easy to use once they’re set up. If your main goal is to get the highest yields possible, then HIDs are the way to go! However, they do require extra setup compared to the other grow lights because chances are you will need a fan to vent out heat from your grow space.

3.) LED Grow Lights

LED grow lights are very popular among cannabis growers as an alternative to HPS grow lights. They tend to run cooler and also usually come with built-in cooling. They can often be plugged into a wall and simply hung over plants which is definitely easier than setting up an HID grow light. LEDs also have great penetration so they don’t need to be moved frequently like fluorescents.

Simply hang an LED light over your plants and start growing!

  • LEDs almost always have built-in cooling that pushes heat up and away from the plants (unlike HID bulbs which beam heat down on your plants and need to be cooled separately). As a result LEDs run very cool and many growers are able to get away without venting heat at all.
  • The smaller size LEDs can be plugged directly into the wall and hung up over your plant, without needing to do anything else. You can just plug them in and start growing!
  • Some growers believe LEDs produce more resinous bud. Combining LEDs with HPS grow lights seems to be getting some growers really great results, though more testing is needed.
  • Although the LED lamp itself usually does run a lot cooler than a similar wattage HPS bulb, they still produce heat and the bigger sizes like 300W+ may need to be vented with an exhaust fan to prevent the grow space from getting too warm.
  • Despite what some sellers may tell you, LEDs get slightly smaller yields per watt than HPS grow lights on average (LEDs commonly yield about 0.5g/watt, though some growers and lamps get better results than others!). There is a learning curve when it comes to getting the best yields from your LEDs, partly because each lamp is different and there are no “standards” to go by yet. A little experience with a specific lamp can improve your yields by a lot!
  • LED grow lights tend to need a lot of space between the lamp and your plants, which means you need a tall grow space to get the best results. This is actually the main thing holding me back from trying LEDs more. Smaller LED panels should be kept 18″ or more away during the second half of the flowering stage to avoid light burning your buds (buds can be burned from too much light even if the temperature is cool), and some of the bigger models need to be kept 30″ or more away from the buds. When in doubt, contact the manufacturer!

If you get very high-wattage LEDs, you may need to vent out heat to keep the grow space cool

For growers who are looking to harvest 1/2 to 1 ounce of cannabis a month, LEDs may be your best choice. At this size, they are super low on electricity, run cool and need almost no setup! They get better yields than fluorescents but don’t run as hot as an HPS of similar wattage.

Note: When shopping for LEDs, make sure they contain some amount of green or white (full spectrum) light. Plants grown without at least a tiny amount of green or white light are very prone to nutrient deficiencies and simply don’t grow as well. Learn more about how light spectrums affect cannabis growth!

Now that you are familiar with all the most common cannabis grow lights I hope your choice is a little easier. I wish I’d had this information when I first started growing indoors 🙂 Happy growing.

There many grow lights that work well for growing cannabis indoors, but they boil down to 3 popular types: fluorescents (CFLs, T5s), HIDs (MH, HPS, LEC) and LEDs. Learn the differences so you can pick the best option for your setup!