You are hereHow to Grow Weed With CFLs
How to Grow Weed With CFLs
by Nebula Haze
Table of Contents
- Learn the Basics
- Get Supplies
- Set Up Your Grow Space
- Start Your Plants
- Vegetative Stage
- Flowering Stage
When growing cannabis indoors, grow space for a garden is often limited! This is where CFL grow lights shine in every sense of the word! If you have a very small grow space, CFLs may be just what you're looking for.
Today, I’d like to share some extra tips and hints for growing cannabis with the super-cheap grow lights which also happen to fit in extremely small spaces... CFLs!
Don't have much space to grow indoors? Try CFLs!
What are CFLs?
CFL stands for "compact fluorescent light" and even though these lights can be found at any hardware or grocery store, they actually give off a really great light spectrum for growing marijuana.
Benefits of growing with CFLs
Easy to find in grocery and home improvement stores
Suitable for very small or short grow spaces, like the inside of a cupboard, small grow tent, or even a 5-gallon bucket
Are growing in a very small or short space
Plan to grow only 1 plant
Want to harvest about 1-3 ounces of bud
Are willing to check on your cannabis every day
Want to 'try out' growing cannabis without investing much
CFLs are not well suited for growers who...
Want to harvest more than 3 ounces each grow
Can’t tend plants regularly
Have lots of space; if you have at least 5 feet of height in your grow space, I recommend upgrading to a more efficient grow light.
Learn more about CFLs vs other popular types of cannabis grow lights
Hint: There are tons of ways to get the most out of your indoor grow space. In the past, we’ve covered how to train your cannabis plants to grow into a short "table" shape that is more efficient under grow lights than letting the cannabis plant grow without interference. These cannabis training techniques are especially well suited to growing cannabis with CFL grow lights.
- Understand the Basics of Growing Cannabis
- Get Your Supplies
- Set Up Your Grow Space
- Start Your Plants!
- Vegetative Stage
- Flowering Stage
You may not want to hear it, but before you do anything related to growing cannabis, you need to make sure you understand the basics of growing cannabis. Skipping this step will cause you all kinds of unnecessary heartbreak!
Today I will walk you through the steps of growing cannabis with CFLs, but you'll get more from this guide if you at least understand the life cycle of a cannabis plant. Taking 20 minutes to read the basics tutorial will answer 95% of the most common cannabis growing questions new growers have. Plus, having a primer will make the learning experience smoother and more fun!
What Do I Need to Understand?
Basically, you need to understand that cannabis plants go from seedling > vegetative stage > flowering stage > harvest. Your job is to give the plant light, water and nutrients, just like any other plant. In the vegetative stage the plant grows only stems and leaves (vegetative growth) while it gets bigger. In the flowering stage the plant eventually stops growing new stems and leaves and starts growing buds. Only female cannabis plants make buds, while male plants make pollen sacs and need to be thrown away immediately. When buds are "ripe" it's time for harvest.
If you feel confused by a lot of that, please take a few minutes to learn the basics of growing cannabis before you proceed to the next step!
You will need light (CFLs), a place to grow, nutrients and a few other supplies to get started growing cannabis with CFLs.
Basically you need...
- Seeds or clones
- A light-proof place to grow (closet, grow tent, etc)
- Growing Medium (soil, coco coir, hydro)
- pH Test Kit or Pen
- Electrical Timer
See a complete list of all the supplies you need (broken down with pictures and links!)
Now it's time to get set up!
Examples of Great Spots to Use CFLs
In a closet
You can literally put your plants in a closet under your CFLs and go. Although it's not the best setup, that's actually what I did for my first grow (see pic!). I did run into problems with heat and ventilation, plus I can't believe I started growing on a carpet without even putting down a tarp or blanket! But it was a cheap and simple way to get started!
Don't do what I did; never grow on carpet! Always put something down to catch spills!
Soon after I started growing, I upgraded my growing environment by getting a grow tent. If you want to start out with a turn-key grow space without any work setting up, you might want a grow tent. You can buy a small grow tent that's perfect for growing cannabis with CFLs! A 2.5'x1.5'x3' grow tent is great for CFLs and will easily fit in the back of your closet. A bigger 2'x4'x5' grow tent is also be a good starting tent size that can be upgraded with bigger grow lights later.
DIY Grow Box, Cabinet or Dresser
Some growers will include both a vegetative and flowering section, or they might dedicate the whole box to one grow.
These small DIY buckets work well with CFLs.
Many new growers already have an idea of where they might grow their plants!
Now it's time to put real plants into the grow space you have created!
- Sprout your seeds (learn how to get seeds and germinate them). Some lucky growers also have access to clones.
- Put your timer on an 18-6 schedule so lights are on for 18 hours a day, with a 6 hour dark period. You can set the schedule however you want so it's most convenient for you. I usually put the dark period during the hottest part of the day to help keep the temperature comfortable for the plant. Learn more about cannabis light schedules.
Set an electrical timer on an 18/6 schedule, then plug in your CFL grow lights
Right after your seeds have germinated, cannabis plants grow just like a normal houseplant. Just give your plants basic care and watch them grow. In the vegetative stage, cannabis really does grow like a weed!
Don't worry, there's more specific info below!
The vegetative stage starts as soon as your young plant starts growing real leaves. At this point, your plant is only making stems and leaves. It grows just like most houseplants at this stage, so your main job is just to provide water, light and nutrients.
- Water your plants regularly, but not too often
- Regularly adjust CFL bulbs so they are within 4" of plants but not burning them.
- Give nutrients (but don't go overboard!) and check pH
- React quickly to any plant problems - most are really easy to fix!
A good way to check if a CFL is too close to the plant is to use the "hand test." Put your hand where the plant is and leave it there for 30 seconds. If it's too hot for you it's too hot for your plants and the CFL needs to be moved further away! Plants can grow a lot in a day, so make sure to give yourself some "breathing room" so your plants don't grow into the bulbs and burn themselves!
Even if you choose not to train your plants, keeping your CFLs close will dramatically increase your yields compared to keeping them further away!
Keep CFLs Close So the Whole Plant Gets Direct Light!
Besides basic care, your main job in the vegetative stage is to train plants to grow short and wide so they'll be able to best take advantage of the CFLs in the flowering stage. This will dramatically increase your yields!
While you don't have to do training to get to harvest, plant training is actually really easy and will reward you greatly!
For biggest yields with CFLs, train plants to grow short and flat using plant training!
It's a good idea to start training when the plant is young, since new stems are flexible and easy to bend (LST). If you start early, you can train your plant to grow flat and wide under your CFL grow lights with only gentle bending and tying down.
Twisty ties are a convenient way to tie down stems after bending them, but you can use just about anything to tie down plants except for things like string, which are sharp and can cut into the plant over time.
Plant twisty ties can easily hook around a stem, while the other side can be hooked to almost anything (like the pot)
Here's an example from above of LST (bending) plus tying down to keep a plant short:
Think about creating a "star shape" from above by bending all stems down and away from the center of the plant.
This is what you're going for - the top of the plants are flat so all the buds are an equal distance from the CFL grow lights. Each bud gets access to lots of light, and grow bigger as a result!
This was just a quick walkthrough, learn step-by-step how to make cannabis plants grow flat and wide!
Vegetative Stage Tactics to Yield More with CFLs
Plant Training - Don't skip at least basic plant training since it's extra important for getting good yields with CFLs!
Adjust CFLs Regularly - You want to adjust your CFLs around your plants as they grow, so make it easier on yourself by setting up your CFLs so they can easily be adjusted in your grow space. Keep in mind that CFL adjustment can be a daily task!
Keep CFLs Close - CFLs should be kept 4" away from the tops of your plants as long as it's not too hot (use the hand test). If possible, try to arrange CFLs so all parts of the plant are within 8-10” of a CFL bulb.
No Shadowy Areas - If you see a “shadowy” area on the plant, it means you need another bulb there, or need to use bending (LST) to rearrange the shape of the plant so all parts are getting direct light.
Don't Move Plants - Try to avoid moving the plants. With CFLs you want to train the plant to grow around the lights which is difficult if the plants move every day. If hand-watering your plant, set up the grow space so you can remove runoff water without having to move the plants.
More Light = Better Results with CFLs. In fact you pretty much can’t really give your plant too much light when growing with CFLs (this isn't true for all grow lights).
- Switch to Flowering When Plants Are Big Enough - Once plants are half the desired size, use your electrical timer to switch your plants to the flowering/budding stage by changing the light schedule to 12/12. Learn more about cannabis light schedules.
In order to switch to the flowering stage you need to switch your CFLs to a 12/12 light schedule using a timer. This means that the plants should get 12 hours of light and 12 hours of dark each day. It's really important to make sure the plant doesn't get any light during the dark period.
Light leaks cause problems! Your grow space needs to completely light proof in the flowering stage!
About 2 weeks after the switch to 12/12, your plant will start making flowers. If it's a female plant it will start making buds, but if it's a male plant it will start making pollen sacs which growers don't want. It's important to remove male plants from the grow space right away because they can pollinate your female plant and give you seedy buds. Learn more about male and female cannabis plants.
You will thank yourself for plant training when you see what happens to all the buds close to the light in the flowering stage!
Flowering Stage Tactics to Yield More with CFLs
Give Buds Intense Light - In the flowering stage, make sure that buds get direct access to intense light & keep CFLs as close to buds as possible without burning them (this will dramatically increase yields with CFLs). Pay close attention to making sure bulbs are close but not too close in the flowering stage.
Give Plants a Comfortable Temperature - Care is basically the same as before, except during the flowering stage it becomes more important to control temperature than ever. If it feels comfortable for you, it's good for your plants, but if you feel hot, they do too. Cannabis plants are much more finicky in the flowering stage, and it's easy to trigger problems if you aren't controlling your environment.
Create a Gentle Breeze - Watch over plants closely, and in addition to making every effort to expose all bud sites to light from your CFLs, try to give all your buds and leaves a gentle breeze. This helps the plant grow better as well as prevents various types of mold.
No More Bending or Training - In the first few weeks after the switch to 12/12, your plant will still be growing new stems and leaves so you can still train plants by gently bending too-tall colas if the stems feel bendy. However, it's important to avoid any more major training once the plant has started making buds.
This plant was grown under CFLs, notice how all the buds are about the same height - this helps increase yields with CFLs by giving you many large colas!
When plants are mature, it's time to harvest!
When it comes to CFLs you basically can't give your plant too much light. With more powerful types of grow lights (like HPS or LEDs) you can light-burn your plants even in cool temperatures, like a sunburn. But with CFLs it's almost incredibly difficult to give too much light so your main job is to get as many bulbs as you can as close to the plants as possible (without burning your plants from heat).
CFLs that are in the 40-42 watt range are great for growing marijuana, and also make great seedling and/or supplemental lighting
Don't get CFLs confused with old-fashioned incandescent light bulbs!
How Many CFLs Do You Need To Grow Marijuana?
Follow these principles with CFLs to get great yields every time:
Start with about 150W worth of CFLs, which is enough light for a small plant
Smaller bulbs = better results
Because the penetration of CFLs is poor, many many smaller CFLs is more effective than a few big CFLs because they can be spread in an array around the plant
For example, 6 x 26W CFLs (at 156 watts total) will be more effective for cannabis growth than 1 x 200W CFL, even though the smaller bulbs use less electricity in total.
Color Spectrum - Not That Important
There are bulbs with different CFL color spectrums and it's generally recommended to get "daylight" (6500k) CFLs for the cannabis vegetative and "soft white" (2700k) CFLs for the flowering stage. Each color spectrum has a impact on how the plant grows, but power (total wattage) is much more important than spectrum in this case! CFLs in any spectrum will do the job! If you do want to get all of one color spectrum, get all "soft white" (2700k) CFLs.
The size and shape of your plant is going to have the biggest effect on how many CFLs you’ll need, and that’s why no “formula” is going to be accurate all the time. Any formula is just a rough estimate, but if you follow the steps in this tutorial you'll get great results every time!
When you’re buying CFLs, they come in different “colors.” Some are more orange/yellow, some are almost blue, and others almost look like bright white daylight on a sunny day.
Having a Bigger Total Wattage is a Lot More Important Than Color Spectrum in CFLs!!!
The truth is that all CFLs will work for growing, but some can help encourage your plants to grow a certain way by imitating the light of the sun during different seasons....
By using the 6500k colored bulbs during the vegetative stage, you’ll be giving your plants more blue light, which can help a plant grow more short and bushy.
However, you can still use bending and training to make your plant grow however short and bushy you want!
The soft white 2700k colored bulbs have more reds/yellows that help your plant "get in the mood" for making buds
Mix of Different Color Bulbs (Daylight, Bright White, and Soft White)
Best suited to Any Stage of Life
An incredible example by grower iskraiskra
What About (5500K) Photography CFLs?
"Will a 5500k photography CFL bulbs work for growing? I know you're supposed to get 6500k colored bulbs in the vegetative stage, and 2700k colored bulbs for flowering..."
"I have a 150w 5500k photography bulb which looks identical to other bulbs rated 5500k specifically sold as "grow bulbs" so could this be used for growing?"
Any CFL will work for growing marijuana. Again, it's much more important to get a high wattage than the right color spectrum. Wattage = light = yields. I've used 5500k photography CFL bulbs in the past and they work great.
As far as spectrum is concerned, blue (6500k) encourages shorter vegetative growth, red/yellow (2700K) encourages longer/taller vegetative growth and flowering.
The 5500k bulbs are in between. However, they can all be used successfully in all stages of growing.
How much light (wattage) will have a much greater affect on your results, and more light/wattage is better with CFLs. For example, I'd rather have 150W of 5500k bulbs than 100W of 2700k bulbs for flowering. The increased light intensity will help your plants more than getting the exact right color spectrum.
The increased wattage will give you more return on yields than getting the proper spectrum.
Light Sockets & Splitters
Make sure to get a light socket for each CFL bulb! This is what you use to get light to your bulbs from the wall.
Get a light socket for each CFL bulb!
A common method for setting up CFLs is to use a 2-way or 4-way splitter plus a light socket extender to fit more bulbs into a clamp light socket (without the extender, they might not fit inside the reflector).
As a bonus to doubling up, setting up more than one bulb per socket can often be cheaper than buying an individual light socket for each light, especially if you buy online. It also is really convenient for arranging CFL bulbs around your plant.
Over the years I've seen many creative solutions for setting up CFLs above cannabis plants indoors! A large part of using CFLs is improvising ways to get them in a proper position close to your plants!
Light splitters like the following are a helpful way to get more CFLs in a smaller place. They also help you use less total light sockets which can save you some money.
Reflect your light for max efficiency
Use the power of reflection to minimize light loss. Cover your walls with something reflective like flat white latex paint (which has 85-95% reflectivity) and/or utilize reflectors to aim more light where you want.
Make walls of grow space more reflective to get more light to your plants. A common way to quickly add a lot of reflectivity is to paint walls with flat white latex paint
Use Black/White Poly Film (also called 'Panda Film')
Use reflectors (or make your own like WasabiMayo does below!)
Learn more about increasing your yields with reflectivity
If you don't have a good growing space, you can easily buy one that's perfect for growing cannabis with great reflectivity!
A 2.5'x1.5'x3' grow tent is great for small spaces. If you have more space, a larger grow tent model will give you a lot more flexibility as far as accessing your plants and being able to arrange your lights.
(choose whether you plan to grow in soil, coco coir, hydro, etc)
- If you're not sure, I recommend starting with coco coir since I believe it's one of the most forgiving ways to grow. It's how I got started and I think it's the perfect way to learn how to grow cannabis without spending a lot of money. Feel free to read my complete guide to growing cannabis in coco coir with CFLs!
- Soil and hydro are also great growing mediums!
Learn more about different growing mediums
- If you're not sure, a simple but very effective nutrient system is from Dyna-Gro. It works well for growing cannabis. You will need to get a bottle of both Grow & Bloom. "Grow" is used during the vegetative stage, and "Bloom" is used in the flowering stage. Dyna-Gro can be used at half-strength to grow cannabis in soil, water, coco coir, or any growing medium.
- When growing in coco coir, I personally use the General Hydroponics Flora trio plus Calimagic (a Cal-Mag supplement). This is the schedule [PDF] I use with those nutrients.
Learn more about cannabis-friendly nutrients
pH Test Kit or Pen
Soil: Maintain 6.0 - 7.0 pH
Hydroponics: Maintain 5.5 - 6.5 pH
An electrical timer is used to make your lights go on and off on a schedule.
The timer I use cost less than $10 and has served me well for years, but any timer will work great!
Don't want to think about it? Here are example setups as far as how many and what kind of CFLs to get! Getting many small bulbs tends to work well and are great for some situations, but getting all those light sockets and arranging all the lights in an easily adjustable way can be a pain. Larger bulb setups let you use fewer bulbs in total to deal with, and have slightly increased penetration, but when they're that big they become more unwieldy and start generating a lot of heat.
A.) Smaller Bulb Setups
Alternative: 6 x 26w 'soft white' CFLs
B.) Medium Bulb Setups
Alternative: 4 x 42W 'soft white' CFLs
C.) Larger Bulb Setups
Alternative: 3 x 65W 'soft white' CFLs
D.) Mix & Match! Just aim for 150W of CFLs in Total to Start
List of Suitable CFLs for Growing Cannabis
CFLs make nice gentle grow lights for seedlings and young plants. CFLs also make great supplemental lighting. Here are CFLs that work well for growing cannabis:
42W CFLs <--- Recommended - great balance of size and brightness
To all you growers on a budget: It's possible!
Check out WasabiMayo's amazing (and budget) CFL microgrow in pIctures...
View full album with a write-up by WasabiMayo right here:
I'm still not sure which grow lights to get... You may be interested in this discussion on the pros and cons of CFLs vs other grow lights for a small space Learn more about CFLs vs other popular types of cannabis grow lights
I want to see a real CFL grow in action! Show me a CFL dresser microgrow with lots of pictures: CFL Micro-Grow Pictures - Week by Week
I'm definitely choosing CFLs... if you know you’re ready to get started growing with CFLs, click here to view my step-by-step tutorial on growing weed with CFLs in coco.
I'm thinking about choosing HPS grow lights instead... Help me get started using HPS grow lights