Compact Fluorescent Lamps (CFLs) explained

Using Compact Fluorescent Lamps (CFLs) is one of the most popular methods of providing indoor grow lighting for plants. These convenient units contain an inbuilt ballast, so don’t require an additional power pack, as is the case with HID (high Intensity Discharge) lighting systems. They do however required an E40 screw-in lamp fitting, so beware they will need a CFL lamp lead or a dedicated CFL reflector to function, and cannot be plugged into conventional household light fittings.

CFLs explained: 125w blue spectrum CFL

Above: A 125 watt Compact Fluorescent Lamp (CFL) grow light.


Like HID grow lamps, Compact Fluorescent Lamps are available in light spectrums suitable for either vegetative or flowering growth (6400K blue light for vegging, 2700K red light for flowering). Models are also available that emit dual spectrum light, so one dual spectrum CFL grow lamp can be used throughout all phases of a plant’s life if required.

CFLs explained: CFL lamp lead

Above: An E40 screw-fit CFL Lamp Lead for connecting CFL lamps to a power socket.

Due to the fact that they are less intense than HID lighting, CFLs are most commonly used for propagation and vegetative growth using a 6400K Blue Spectrum model, either used on their own or as supplementary lighting in conjunction with a metal halide HID set-up.


To set up a CFL lamp, simply screw the lamp into a CFL lead and plug it into a power socket, preferably via a timer in order to control the light cycle in the grow room.

CFLs explained: E40 screw fitting


Above: Screwing the CFL grow lamp into a CFL Lamp Lead

CFLs explained: grow light timers


Attach the 3-pin plug to a timer to control the grow room light cycles

When used as supplementary lighting, CFLs can be hung vertically at the side of the grow room or grow tent. Be sure to set the timer on the CFL lead to the same settings as any other lighting in the grow room.

For propagation, many growers leave CFLs on for 24 hours and don’t use a timer, but we recommend always giving plants at least a few hours rest in order for them to perform at their best, much as we need rest to be at our best!

We recommend for vegetative growing that you set the timer to on for 18 hours on and six hours off. If switching to 2700K Red Spectrum CFL grow lamps for flowering growth, switch the timer settings to 12 hours and 12 hours off. Be sure to ensure that the plants are in complete darkness during the ‘night’ period, as exposure to light can confuse the plant into reverting to the vegetative growth associated with longer, mid-summer light cycles.

CFLs explained: supplementary grow room lighting

Above: A Blue Spectrum, 6400K CFL grow lamp hanging vertically at the side of a grow tent as supplementary vegetative lighting.


Dedicated CFL reflectors can be used to hang the lamp horizontally and reflect all the light downwards on to the plant canopy.

CFLs explained: CFL in dedicated CFL Reflector



Above: a 250 watt CFL positioned horizontally above the plants using a CFL Reflector.

What types of CFLs are available at Straight Up Hydroponics?

Here at Straight Up Hydroponics you can obtain the following models of Compact Fluorescent Lamps:

CFLs explained: 65w CFL

Secret Jardin’s 65 watt Pro-Star CFL grow lamp. A perfect 6400K, blue spectrum model for small areas. We love this handy little CFL – it’s also great for indoor-grown herbs.

Maxibright’s 125 watt 6400K blue spectrum CFL – great for bringing on young plants. Vegetative growth phase grow lamp.

Maxibright’s 125w 2700K red spectrum CFL – for the flowering phase in small-scale grow rooms.

250w CFL. 6400K. Blue spectrum. Vegetative phase grow lamp.

Red spectrum CFL grow lamp. 250w. Good for flowering growth.

CFLs explained: Dual Spectrum CFL from Maxibright!

Maxibright’s dual spectrum CFL grow lamp. Great all-rounder. Blue and red spectrum for both grow phases. Nice choice of lamp, especially with a CFL reflector. Just add a timer and you’ve got all the light you need for a small-scale indoor grow!

If you require any more information before choosing which Compact Fluorescent Lamp (CFL) is the best for your needs, feel free to give our shops a ring. Happy growing!