Using CFLs to grow autoflowers
CFL or Compact Fluorescent Lights are bulbs that use the fluorescent (daylight) tube technology but can be placed in regular household E27 sockets. The way that these bulbs work is by fluorescence and that means that there is a gas inside a glass tube that gets excited when electricity is passed through it. When the gas gets excited it produces ultraviolet waves that passes through the glass wall that is usually coated with phosphor from the inside. As this ultraviolet light passes through this coating the Phosphor starts to fluoresce and that in fact produces the visible light waves.
This technology is nothing new and it has been used by fluorescent T12, T8 and T5 tubes for decades but because those lights need ballasts to sustain a continuous current they can’t be made smaller. Here comes in the CFL lights that have a ballast in the base of the light just above the socket contact. This ballast is usually the hottest part of the light because it needs to transform electricity from your regular E27 socket output to one usable by that folded fluorescent tube. In fact if you have seen a T5 or T4 fluorescent tube light then you can imagine how that long tube is folded in various curves and fit together to form a compact bulb like shape.
How CFL lights work on autoflowers
Many growers think that because CFL lights are less efficient in their lumen output per watt that they would grow smaller plants but that is not the case because fluorescent lights have a greater photo synthetically active radiation index than HID grow lights. This means that light produced by CFL lights is more usable by plants and there is less light that is created and simply lost because plants cannot use that light. There are various spots on the spectral scale where cannabis uses light more and less and you can see that light usage scale at the image behind this paragraph. but for example the green light is entirely unusable and also yellow light is used in low amounts and if we think that HPS lamps create most of their light in the yellow spectrum but CFL lights produce Blue or Red light depending on the bulb type then we can imagine how less efficient light can produce the same and maybe bigger yields.
Basically if you use a proper grow guide and a lot of CFL lights you can grow better plants than HID bulbs could produce!
CFL variations and efficiency
Compact fluorescent tubes come in different variations and shapes and they also come in various Wattages and lumen output and not all of them have the same efficiency ratings.
Basically when looking at various different shapes you will find that all of them can be divided in two categories the Spiral and Tubed shapes and usually the tubed ones are longer but thinner and the spiral bulbs are wider but shorter but they can go both ways so just pick the bulb that suits your need.
As for the efficiency ratings the shape doesn’t matter and almost always the wattage is the main thing to look and and calculate the lumen per watt ratios. Here are some sample efficiency ratings of CFL bulbs. There may not be completely accurate and you should calculate them before buying any light bulb.
- 13 W = 825 lumen => 63 lumen/watt
- 26 W = 1610 lumen => 61 lumen/watt
- 42 W = 2700 lumen => 64 lumen/watt
- 45 W = 2800 lumen => 62 lumen/watt
- 85 W = 4250 lumen => 50 lumen/watt
- 125 W = 7,000 lumen => 56 lumen/watt
- 200 W = 9500 lumen => 47 lumen/watt
- 300 W = 13,975 lumen => 46 lumen/watt
From these ratios you can see that the most efficient CFL bulbs are at the start of the range from 12 W to 45 W but 13 W bulbs are too weak and you would need a lot of them to grow cannabis so the best CFL lightbulb for growing marijuana is the 42 W one because it is the most efficient and will grow the biggest plants. Because that 42 W bulb emits around 2700 lumens you will need a couple of them to truly utilize the light and get maximum amount of bud production because cannabis plants need from 5000 to 10000 lumens per square feet of growth so you should measure your growing area and calculate the total volume and if for example it is 10 square feet you would need at least 20 CFL bulbs to support the plants that are growing there but you can place them all around those plants and get the best light penetration and growth.
CFL color temperatures
As you may know by now Cannabis plants need different kind of light for various growth stages and it is best to supply more Blue light at the seedling and vegetative stages but give more red light at the flowering stage but basically these plants use almost all color spectrum light except green and CFL light come in different kind of spectral outputs that are measured in Kelvin (K). There are the two main categories like the 6500K for seedling and vegetative growth and 2700K for Flowering but because you will need a lot of bulbs to grow great buds you can supply both spectrum bulbs and even the middle range 3000K and 4000K ones because they will have different spectral outputs and your plants will receive more diverse light that will be more usable to them. I usually give my plants the majority of 6500K light at the vegetative stage and a majority of 2700K or 2500K light at the flowering stage but also have a few opposite spectrum lights and one or two middle range ones.
Why use CFL lights?
As you may know CFL light can be as efficient in growing marijuana plants as HPS bulbs but you need a lot of them but that can be a very helpful thing because you can place them around the grow room and around your plants to maximize the light usage. This can be done because CFL light emit low amount of heat and your plant can be within 2 inches (5 cm) of the lamp and won’t get burned and it is better to have multiple light sources than one big one because you decrease shadows and more leafs get light and that means faster growth!
- Cheap bulbs
- Easy to replace
- Will fit into regular E27 bulb sockets
- Come in various color temperatures
- High PAR efficiency
- Stay cooler than HID lamps
- Can be easily placed around plants in different angles
- Higher wattage bulbs get less efficient
- You will need many bulbs to supply adequate light amount
- CFL’s have shorter lifespans than LED lights
As you can see CFL lights are good for growing cannabis and you just need a lot of them to grow dense buds and get big yields but they are cheap, easy to use and don’t get as hot as High Discharge Lights!
This Cannabis CFL growing post was written by Midowo from Autoflowering cannabis Blog
Many thanks to him!!