How to choose CFL bulbs for your home grow

Whether you're a minimalist just looking to grow some cannabis in your window or an enthusiast looking to invest in a more fleshed-out system, chances are you already know how important light is for your plants. (And if you don't, the answer is very!)

Aside from the finer points of nailing down your supplemental lighting game — distance from the plants, the quality and spectrum of the light, lighting schedules and timers — perhaps the best place to start your journey is with the bulbs themselves. While you can park a plant in a window and let it do its thing, if you want to coax your indoor plants into optimal productivity and yields, supplemental lights are the way to go.

There are lots of lighting options available to the home grower, but for now, let's dig into one specifically: compact fluorescent light (CFL) bulbs. Widely available and simple to use, CFL bulbs are often employed by home growers of all skill and interest levels. So let's unpack them for you.

cannabis plant
Widely available and simple to use, CFL bulbs are often employed by home growers of all skill and interest levels.
Photo by: Dimitri Newman/Weedmaps

What are CFL bulbs?

Compact fluorescent light bulbs use a combination of argon gas and mercury vapor to produce light. When exposed to an electric current, the argon and mercury combination generates an invisible ultraviolet light. This light hits a fluorescent coating on the inside of the tube, and voila, visible light.

CFLs were originally developed to replace incandescent bulbs, which are not all that energy efficient. Compared to incandescent bulbs, CFLs last 10 times longer and generate much less heat (which is actually a good thing for indoor cannabis grows). Thanks to LED lights, they're no longer the most energy-efficient option, but they do require less wattage to deliver the same amount of lumen output as incandescent bulbs.

What is better, LED or CFL bulbs?

Speaking of LEDs, which is better? LED lights have quickly become quite popular with indoor cannabis growers, and with indoor gardeners in general. Aside from being useful in growing devil's lettuce, LED lights can be useful in growing regular lettuce, along with kale, herbs, and other consumable plants.

While many indoor cannabis growers will definitively conclude that LEDs are better, both CFLs and LEDs have pros and cons.

CFL bulbs for cannabis home grow
LED lights have quickly become quite popular with indoor cannabis growers.
Photo by: Gina Coleman/Weedmaps

The pros of CFL bulbs

We'll get into the shifting legal landscape of CFL bulbs in a minute, but generally speaking, CFL bulbs are still pretty easy to find at local hardware stores and even grocery stores in most states. 

Unlike high-intensity discharge (HID) lights that are often used to grow cannabis, CFL bulbs don't need special fixtures or setups — they will screw into any lamp you already have for incandescent bulbs. This — combined with the fact that they don't generate a ton of heat — makes CFL bulbs good for small grow spaces. CFLs also come in a variety of temperatures, meaning you can adjust to the plant's need in the vegetative and flowering stages of growth.

Finally, CFL bulbs require the smallest initial investment compared to HID and LED setups. When thinking about electricity bills, CFLs are the middle of the road when compared to expensive HID lights and inexpensive LED lights.

To summarize the pros of CFL bulbs, they are:

  • Easy to find
  • Easy to use, no special or custom fixture needed
  • Good for small spaces
  • Cooler than HID lights
  • Cost-effective in the short-term
  • Available in a variety of temperatures for vegetative versus flowering stages of growth

The cons of CFL bulbs

On the flip side, you will need to adjust your setup regularly as your plant grows. CFLs have a limited range of efficacy, and the plants need to stay fairly close to the bulbs. Do the “back of the hand test” by holding your hand over the top of the plants for 30 seconds to see if it's too hot, but generally speaking the sweet spot is about 4 to 5 inches between bulb and plant.

While cheaper for initial setup, CFL bulbs have a shorter lifespan and are less efficient than LEDs, meaning they will cost more in the long-term. As mentioned, CFLs also contain a small amount of mercury, which can pose some risk to you and other living creatures in the vicinity should you break one. (Read on to learn more about that.) Because of this, they also require special disposal to avoid sending mercury into landfills.

CFL cons include that they:

  • Have a limited range of efficacy
  • Will require adjustments as the plants grow
  • Are more expensive in the long run 
  • Contain a small amount of mercury
  • Need special disposal
LED and CFL bulbs for growing cannabis
When it comes to growing cannabis, there are two types of CFL bulbs to consider: daytime or daylight and warm white or soft white.
Photo by: Gina Coleman/Weedmaps

How to choose the right CFL bulbs

When it comes to growing cannabis, there are two types of CFL bulbs to consider: daytime or daylight and warm white or soft white. The difference between these two types of bulbs is their color temperature, and color temperature needs change as the plant matures.

If you think about your lighting game as trying to mimic the natural cycle of sunlight, then it would make sense for plants to need a stronger and more intense light early in their life when they'd be happily growing out in the summer sunshine. That's the daylight CFLs. Then, during the flowering stage, your plants will benefit from the gentler soft white CFLs since out in nature, summer would be turning to fall when sunlight becomes weaker.

In an ideal setup, you should be using both types of bulbs to meet the needs of your plants at different stages of their life cycle: daylight for the vegetative stage and warm white for the flowering stage.

Can you still buy CFL bulbs?

The answer depends on where you live. As of this writing, the fate of CFLs is unclear due to some backtracking by the Department of Energy around efficiency requirements for light bulbs that were supposed to come into effect back in 2019. The matter is currently being litigated and, much like cannabis laws, there is a patchwork of regulation that varies by state.

Are CFL bulbs dangerous?

Compact fluorescent light bulbs do contain a small amount of mercury, and mercury can be dangerous. On the plus side, manufacturers have drastically decreased the amount of mercury they use in CFLs and are trying to reduce that amount even further.

The only real risk CFL bulbs pose is if you smash them. When that happens, the mercury vapor escapes and it could pose a risk to you, other humans, and pets. If you break a CFL bulb, be sure to keep kids and pets away, open the windows, and don't vacuum. The Environmental Protection Agency provides a very helpful guide to cleaning up broken fluorescent bulbs.

Bottom line

Compact fluorescent light bulbs have lots of pros for the novice grower: ease of use, minimal investment, and decent efficiency. That said, they do carry some minimal risk, are less environmentally friendly than other options (like LEDs), and will cost more in the long term. 

To make sure you cover the bases throughout your plant's life, be sure to use daylight CFLs during the vegetative stage and warm white CFLs during flowering. And don't forget, if you do choose CFLs for your indoor grow, do the planet a solid and make sure you properly dispose of them.

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The information contained in this site is provided for informational purposes only, and should not be construed as medical or legal advice. This page was last updated on June 14, 2021.