How to Grow Cannabis with Fluorescent Lights?

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Added 29 July 2023

Let’s go back in time a bit. It’s your biology class and your teacher is talking about photosynthesis in plants. It’s a process that must’ve sounded magical at the time, especially if the teacher wasn’t good at explaining. But the process is pretty simple. Photosynthesis is where a plant uses energy from sunlight to produce energy, which helps it grow bigger and produce the flowers that we’ve all come to love and cherish. 

This process occurs naturally when you’re growing cannabis outdoors. The sun is one giant grow light that produces enough light in the right color for the right time, ensuring optimal cannabis plant growth. But what happens if you want to grow cannabis indoors?

The answer is: grow lights. And while there are a few types of grow lights, one that stands out is fluorescent lights. While they may not be your first choice, they are terrific grow lights, especially if you are a beginner or a hobby grower. 

So, let’s learn all about fluorescent grow lights and how you can use them to grow healthy cannabis plants. 

What are Fluorescent Lights?

What are Fluorescent Lights?

Fluorescent light is a type of grow light that produces light via a chemical reaction within the bulb. The bulb contains certain gasses and mercury, which produce phosphor coating upon reaction. This phosphor produces UV light, which is beneficial for the cannabis plant. 

While we can’t see UV light, your cannabis plant can really benefit from this type of light. UV light is classified as abiotic stress for plants. Thanks to UV rays, your plant begins to produce secondary metabolites to protect itself from the light, and these metabolites are nothing but cannabinoids and terpenes — don’t we all love these? 

Apart from producing UV light, fluorescent lights offer other benefits for the cannabis plant. They are more efficient and run cooler than HID or HPS lights, and are much cheaper to buy than LED lights. 

These fluorescent lights allow you to create lighting conditions within your grow room that mimic the natural sunlight. And for many growers, especially those on a budget, fluorescent lights are often the ideal choice as you’ll learn later in this article. 

Fluorescent Grow Lights Types

Fluorescent grow lights come in various types, which may be confusing for growers at first. Some of the most popular types are CFL, T5, T8, and T12. Essentially, these naming systems signify the diameter and wattage of the lights, where the letter T stands for tubes and the number indicates the diameter. For example, a T5 light is a tubular fluorescent light whose diameter is five-eighths of an inch. 

Here’s more on the types of fluorescent grow lights:

  1. T12: These were the first types of fluorescent lights that found their way into cannabis grow rooms, and these lamps produced light by electromagnetic induction but they weren’t really efficient for gardening.
  2. T5 and T8: These two categories are often represented together since they are more similar than different. These lights came out later and were more powerful and efficient than T12 lights. Here, T5 has the upper hand for being the more efficient and powerful of the two. 
  3. CFL: CFL stands for compact fluorescent lights, and these are the lights that we often use in our homes. Since these are not grow lights by nature, they work best for smaller setups where you can jerry-rig a CFL bulb to a socket suspended above your cannabis plant. 

Out of all these lights, the best type of fluorescent light is T5 followed by T8, but if you are in a pinch, you can get by by using CFLs or T12 lights. 

Fluorescent vs LED Grow Lights 

LED grow lights are all the rage in the horticulture industry, but how do they differ from fluorescent lights? Here are a few major differences:

  • LED lights are way more energy efficient than fluorescent lights 
  • Fluorescent lights are cheap and easy to buy anywhere on Earth
  • Thanks to industry standards, you know exactly what you’re getting into with fluorescent lights 
  • Fluorescent lights come in a variety of color options, but LED lights can produce lots of colors from a single panel 
  • LED grow lights produce more heat than fluorescent grow lights 
  • LED grow lights last over a decade but fluorescent ones can barely last for over a year

In comparison, LED grow lights look like the better option — and for good reason. LEDs are a relatively new innovation and are touted as the future of grow lights, potentially putting HPS and HID lights out of business. However, LED lights are expensive and hard to pick. For most new or hobby growers, fluorescent grow lights work just fine. 

Advantages of Fluorescent Grow Lights to Grow Cannabis

Advantages of Fluorescent Grow Lights to Grow Cannabis

Fluorescent lights may not always be the first choice, especially considering LED and HID lights, but they do serve a purpose in many cannabis grow rooms. Here are some of the reasons why you may want to consider using fluorescent grow lights for growing cannabis. 

1. They are Readily Available 

One of the biggest advantages of fluorescent lights is how easy they are to source. Even if you live in the remotest part of Siberia, you can still find reliable and powerful fluorescent lights at the general store. Sure, they may not be grow lights but they can work if you use the right methods. 

2. They are Cheap

Along the same lines, since fluorescent lights are so common and old-tech, they are super cheap to purchase. In fact, you wouldn’t be making financial mistakes even if you used them as disposables — that’s how cheap they are. Of course, a T5 fluorescent light is a bit expensive, but it’s pennies compared to HIDs or LEDs of the same light production capacity. 

3. Fluorescent Lights are Efficient 

Leave LEDs aside for a minute — nothing beats LEDs when it comes to energy efficiency. However, fluorescent lights can give LEDs a run for their money, considering how expensive LED grow lights are to produce. 

For example, for a medium-sized cannabis setup, you would need around 800 watts of energy to produce enough light for your cannabis plants. So, during the vegetative stage, when you run your grow lights in an 18/6 light cycle, you will spend roughly $2 a day to run fluorescent lights. 

On the other hand, an 800W HPS bulb would set you back by around $8 a month in the same 18/6 light cycle. And we’re not even considering the cost of ballast and cooling fans that you require for running HPS bulbs. 

If you compare fluoros with HIDs and LEDs, you’ll notice that fluoros come in lower wattages and draw less energy. This is particularly advantageous if you are worried about electricity costs. Less energy consumption also equates to less heat, which means that the growing environment will be stable. 

That said, comparing HIDs and fluorescents is like comparing apples and oranges since HIDs produce way more yields than fluoros; however, they are pretty decent for beginners who want to test the waters before they start swimming. 

4. They Don’t Heat Up Too Much 

Why do you need cooling fans for HPS bulbs? Because they tend to run hot — a good set of HPS bulbs can raise the ambient temperature of your grow room and even cause heat stress to your cannabis plants unless the heat is managed by external fans. That’s not the case with fluorescent grow lights. 

With fluorescent lights, you don’t have to worry so much about heat because they run much cooler and don’t require heat mitigation devices like cooling fans or external fans. And, you certainly won't need air conditioners unless you live in a really hot location. Even if you were to place fluorescent grow lights 2 inches from your plant — which you shouldn’t — your plants won’t burn. The same can’t be said about LED and HID lights. 

5. Suitable for Small Spaces

Fluorescent lights are particularly fit for cultivators with limited growing areas or those that want to maintain discretion when it comes to growing cannabis. As fluorescents are compact with less heat output, they fit easily in cabinets or grow tents. Thanks to their flexibility, you can start growing immediately without having to invest in complex setups that require more space and are expensive. 

6. Easy to Set Up

Fluorescent lights are simple and you don’t need to research too much about how to use them. This means that you can set them up in a jiffy without worrying about complicated electrical work. Needless to say, this convenience makes it easy for even amateurs to start growing marijuana in their own homes. 

7. Supplemental Lighting

While fluorescent lights might not be one of the most effective light choices, you can use them to supplement extra light in larger grow tents. If you combine them with HID lights or LEDs, fluoros can fill gaps and provide additional coverage to ensure more uniform light distribution across the entire cannabis canopy, thereby helping you get better yields. 

8. Reduced Maintenance

Fluorescent lights are popular for their sturdiness. Although they won’t last as long as LEDs that run for more than 100,000 hours in many cases, you can expect at least 15,000 hours from fluoros. Considering that you’re paying much less for these bulbs, it’s a decent return on your investment. It’s great for hobby growers that want to grow just a couple of plants and see how it goes. If you’re using fluoros for clones and seedlings, you don’t need to replace the bulbs very often. 

9. Adaptability

Fluorescent lights can be found in numerous types such as T5 tubes and small fluorescent lights (CFLs). T5 tubes are superb for offering consistent light coverage over a bigger location making them ideal for several plants (if you purchase several T5 tubes). CFLs on the various other hand, are smaller and are more suited for clones or small plants. You can even use CFLs as supplement lights in areas where there’s less light coverage in the grow room. 

10. Ideal for Propagation 

The blue range of fluorescent lights is especially valuable during the vegetative phase when plants concentrate on establishing solid stems and leaves. They are great for seedlings, clones, or small plants as the blue light encourages compact and bushy growth. Utilizing fluorescent lights on seedlings establishes the structure for healthy plants before you switch to heavy-duty lights during the blooming phase.

11. They Distribute Light Uniformly

The final benefit of using fluorescent grow lights is their uniform light distribution. Since they are built in a particular way and how they produce light, the light is always emitted in a uniform way. This is terrific for your cannabis plants as there won’t be any light hot spots on the canopy. 

To conclude, while fluorescent lights might not provide high-intensity lights, they have some advantages for growers with specific needs. Whether you have a limited budget or just want to experiment with a few small plants, fluoros can help. 

Disadvantages of Fluorescent Grow Lights to Grow Cannabis

Disadvantages of Fluorescent Grow Lights to Grow Cannabis

Despite the upsides, fluorescent grow lights do have some downsides, which are as follows.

1. You Need to Change Them During Each Stage of Growth 

If you’re growing cannabis with LED lights, a single light works for the entire life cycle of the plant, but the same isn’t the case with fluorescent grow lights. In this case, you need to change them during each of your plant’s growth stages so your cannabis plant can get a suitable spectrum of light. 

For example, you need to use 6500K fluorescent grow lights during the vegetative stage and switch to warmer 2700K during the flowering stage. This is because cannabis prefers cooler light during vegging and warmer during the flowering stage. 

2. They Aren’t as Powerful as LED or HID Lights

Another major downside of fluorescent grow lights is that they are not as powerful as LED or HID grow lights. So, they only work for smaller cannabis operations and it is often recommended to prune and train your plants to improve light penetration when using fluorescent lamps. 

3. The Yield Won’t Be Extraordinary

Fluorescent grow lights are excellent but they only provide the bare minimum of what your plant needs. As a direct consequence of limited light intensity and penetration, the yields under fluorescent lights are generally lower compared to those grown under more powerful lighting options. In addition, the lack of intense light during the flowering stage can result in smaller buds and reduced resin production, ultimately leading to less overall harvest weight. So, while they can grow healthy cannabis plants with an average yield, you shouldn’t expect extraordinary yields that you would from LED or HID grow lights. 

4. They Don’t Last Very Long 

If you don’t intend to grow cannabis in the long term, fluoros are great for you; however, if you plan to grow several plants stretched over multiple cycles, fluoros aren’t all that great as they don’t last a long time. As mentioned already, most of them have a life of about 15,000 hours, so you can only grow a few batches of plants before the lamps die out. But since they are cheap to replace, this shouldn’t be a major deal breaker for most cannabis growers. 

5. Much Less Light Penetration

Fluorescent lights release light in a linear pattern that ultimately restricts their capacity to permeate deep into the canopy. As a result, the lower parts of the plant don’t get too much light, resulting in underdeveloped buds with reduced yields. 

6. Longer Growth Period

Due to their low-intensity light, cannabis plants may take longer to reach their desired size during the vegetative stage. This is not really a disadvantage if you’re growing photoperiods, but the plants grow a bit slower compared to being under HIDs or LEDs. If you’re growing autos, though, this could be a slight problem as longer vegetative periods can extend the overall cultivation time.

7. Ineffective for Flowering Stage

The blooming phase is a vital phase that determines the potency and size of the buds. Fluorescent lights are not equipped to provide the specific light spectrum needed during this stage, which requires an increased amount of red light. Without sufficient red light, cannabis plants might not develop dense and large buds as they would under more suitable light sources designed for flowering. 

8. More Lights Needed

To make up for the reduced light intensity and coverage, you may have to use numerous fluorescent lights to cover the canopy. Although this won’t be a problem if you have a small grow room, it can be problematic if you’re growing many plants in big areas. This can lead to higher energy costs that defeat the purpose of using fluoros. 

9. Frequent Bulb Replacement

Although fluorescent bulbs have a longer lifespan than traditional incandescent bulbs, they still require periodic replacement. Over time, the light output of fluorescent bulbs diminishes, leading to reduced light efficiency. Growers must replace bulbs regularly to maintain adequate light levels for healthy plant growth, adding to the ongoing maintenance and costs. 

10. Lack of Light Spectrum Control

Fluorescent lights are not as customizable when it comes to adjusting the light spectrum for different growth stages. While certain fluorescent tubes or bulbs might be labeled as "warm" or "cool", they lack the precise spectrum control found in more advanced lighting options like LED grow lights where you can fine-tune the spectrum. 

As you can understand, while fluorescent lights have their benefits by being cost-effective and ideal for clones, seedlings, and plants during the early vegetative stage, they are inefficient to be used for the entire life cycle of the plant, especially throughout the blooming phase.

If you want good yields fast, you’re better off using fluoros just for clones and seedlings and using other high-intensity lights to grow cannabis. 

How to Choose the Right Fluorescent Grow Lights to Grow Cannabis?

How to Choose the Right Fluorescent Grow Lights to Grow Cannabis?

Choosing the right grow light is never easy; it’s a complex subject, but let’s make it easier for you. 

First, you need to select the right type of fluorescent light. As stated previously, there are two primary types of fluorescent lights you can use to grow marijuana: T5 and CFLs. 

T5 lights are much more effective than CFLs. They can be found in different sizes, varying from 2 feet to 8 feet, and are appropriate for bigger grow rooms or for growing several plants. T5 lights are great for commercial cultivators seeking high coverage and output. 

On the other hand, CFLs are smaller and perform well in smaller grow rooms. You can also use them for seedlings and clones or plants that are early in the vegetative stage. They come in different wattages and configurations, providing you with more flexibility in your setup. CFLs are often used by beginners or hobbyists with limited space and budget constraints.

Next, you need to know two terms: wattage and kelvin scale. Wattage is the amount of energy the light consumes, since fluorescent grow lights’ light emission depends on the wattage — it’s directly proportional to how much energy they consume. 

On the other hand, the Kelvin scale is the temperature of the grow lights, i.e., the light spectrum they produce. Some light panels produce warmer light and others produce cooler light, and you need to pick the right one based on your plant’s growth stages. 

When it comes to choosing the right fluorescent grow lights for your cannabis setup, you need to pick the highest possible wattage for your growing space. The higher the wattage, the more the light. You can also refer to lumens when picking the right intensity for growing lights. 

Ideally, each cannabis plant should have at least 10,000 lumens of light. So, if your fluorescent bulb produces 2,500 lumens, you need four of them for a single plant. If you’re using lumens — it’s more reliable than wattage — it’s ideal to invest in a good lux meter. And if you’re using wattage, a 42W CFL light produces 2,700 lumens. You can find many accurate wattage-to-lumen calculators online for fluorescent grow lights

Let’s move to the Kelvin scale now. Most fluorescent grow lights come in 2700K, 3000K, 4100K, and 5100K modes. The lower the kelvin scale, the warmer the grow light, which is suitable for the flowering stage. And the higher the kelvin scale, the cooler the grow light, which is ideal for the growth stage of cannabis. You can even use lights that fall between these ranges to get a good balance of color, depending on your preferences. 

Here’s an ideal guideline for the color temperature you need to pick for your grow lights:

  • 5000K to 6500K for the vegetative stage, since it mimics daylight colors 
  • 2700K for bloom since this color temperature is rich in the red spectrum, which promotes better bud development 

Apart from these factors, stick to well-known brands and you’re good to go. You can even use regular home-use fluorescent lights, but make sure you pick one with adequate wattage and the right color temperature.

How to Set Up Fluorescent Grow Lights for Cannabis Plants?

How to Set Up Fluorescent Grow Lights for Cannabis Plants?

If you’ve made up your mind about using fluorescent grow lights, here’s a guide to help you set it all up. Remember, this guide focuses on a smaller space, considering you’re working with fluorescent grow lights, but you can feel free to tweak the steps to suit your individual cannabis operation. 

1. Gather the Supplies

Before you begin, you need to gather the supplies. Let’s assume you are only growing a single cannabis plant, so you need at least 150W to 200W of fluorescent lights. So, you can get two 50W bulbs of 5000K to 6100K and two 50W bulbs of 2700K. You can feel free to tweak this based on your preferences and setup. 

Here, we’d recommend you get multiple smaller lights than a single big one. This is because, as you already know, fluorescent lights have poor light penetration, so many smaller bulbs can help light get through the canopy more easily. Remember to stick to around 10,000 lumens of light, regardless of the size of the bulbs you choose. 

But there’s a flipside — don’t choose fluorescent lights that are too small as they’d be pointless. Ideally, stick to at least 40W fluorescent grow lights. 

If you’re using fluorescent grow lights, chances are this is your first cannabis plant. Fortunately, these grow lights are versatile and can work with a variety of indoor cannabis plant setups, such as the closet, PC towel, grow tent, grow room, or most kinds of hydroponic systems. 

Depending on the size of the lights and your setup, you need to pick the right method to suspend the lights above your cannabis plant. The sky’s the limit here — pick a system that works best for you. It could be suspending the panels with rope, using a wooden frame to hold them in place, or using zip ties or tripods to hold them up. 

2. Using Fluorescent Grow Lights During the Seedling Stage

Fluorescent lights can be used during the seedling stage of your cannabis plant. Start by germinating your cannabis seeds, and when they’re ready, transplant them into their containers. At this stage, stick to an 18/6 light cycle with the CFL lights and water your plant adequately. 

Here’s a tip: even if you move to better grow lights in the future, stick to fluorescent lights for the seedling stage. They are gentle and won’t burn the delicate seedlings. 

3. Using Fluorescent Lights During Vegging

Once your cannabis plant has moved into the vegetative stage, things get real. During this growth stage, your cannabis plant needs more daylight, which is often cool white in the outdoor environment. So, use daylight bulbs that produce a light spectrum of 5000K to 6500K. 

Next, place the lights around 4 inches of your plant’s canopy, but not too close. A good way to check this is to place your hand on the canopy — if it feels warm on your skin, the lights are too close to the plant. Move them up a bit. 

Next, water the plant regularly, avoid overwatering, and give the right nutrients. Also, train your cannabis plants. This will improve light penetration from your fluorescent grow lights, ensuring all parts of the foliage get equal amounts of light for consistent growth. 

Training will also ensure your cannabis plants don’t grow into light panels. This is the stage where plants grow fast, and since fluorescent lights are so close to the plant, there’s always a risk that your plant will grow into them. Training prevents this. Some of the best training methods you can use here include LST, super-cropping, ScrOG, NFT, pruning, FIMming and topping, and monster cropping. 

4. Using Fluorescent Grow Lights During Bloom

When your cannabis plants are ready, you need to switch the light cycle so your plant starts flowering. So, switch the light cycle from 18/6 to 12/12. This switch in the light cycle signals the plant that winter is close and it’s time to start producing flowers — applicable for photoperiod cannabis plants. 

During this growth stage, use warm white bulbs with a kelvin scale of around 2700K, since these bulbs produce more red-dominant light, which is terrific for bud development in cannabis plants. If you don’t mind spending a bit, you can even use HPS lights during this stage. 

At the same time, pay close attention to your plant, watch out for flowering stretches, manage the temperature, avoid training your plant unless absolutely necessary, and religiously follow the light cycle. 

5. Pro-tip: Use Reflective Materials

CFL grow lights have a good spread but they aren’t as powerful as their rivals like LEDs or HIDs. So, you can use reflective materials around your cannabis plant to maximize light penetration and minimize light wastage. These materials will distribute lighting more evenly across the foliage, leading to better plant health and growth.

Some of the best reflective materials for growing lights include Foylon (90% to 95% reflection), Mylar (92% to 97% reflection), matte white paint (80% reflection), panda films (80% reflection, and orca films (95% reflection). Don’t hesitate to experiment and figure out what works best for you. 

Depending on the reflective material you pick, you can cover your plant in various ways. You can build a fence around the plant, you can prop the material like a tent over your plant, or strategically place pieces of it around to improve light penetration. There is no right or wrong method as long as you are minimizing the loss of light. 

Summary: How to Grow Cannabis with Fluorescent Lights?

Fluorescent grow lights are nothing extraordinary. They are bare basics grow lights that you may already be using to light up your living room. And while there are better alternatives out there, for many growers, fluorescent grow lights work just as well. It’s a perfect example of don’t fix if it ain’t broken. 

They have several benefits: they are cheap and easy to buy, energy efficient, easy to use, and produce even light throw. So, pick the right wattage or lumens of fluorescent grow lights (around 10,000 lumens for a single plant), and set it all up. 

Use cooler lights during the seedling and vegetative stages, and switch to warmer fluorescent grow lights during the flowering stage. It may seem like too much effort but the results will more than surprise you. And to learn more on how to grow cannabis the right way, stay tuned to our blog. 


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