Best lighting for indoor cannabis growing

Grow lights for indoor marijuana growing have been changing lately due to technological developments in lighting and due to discoveries of how different light spectrums are used by cannabis plants.

Simply sticking a bright light over your plants for the duration of their grow and flowering cycles is longer seen as adequate. These days smart indoor marijuana growers will use different types of lights at different stages of the plants’ growth.

We’ll look at these newer grow lights for indoor marijuana in a minute. But to start, let’s take a look at the old standby lights that still many growers use – perhaps because its easier to use what you know than to contemplate change.


HIDs (High Intensity Discharge Lamps)

high pressure sodium grow lights hpsMost indoor marijuana growing gardens used to use High Intensity Discharge (HID) lamps. The two types most commonly used were Metal Halide (MH) which produce an abundance of light in the blue spectrum promoting plant growth.

The other kind are High Pressure Sodium (HPS) lamps which emit an orange-red glow triggering hormones in plants to increase flowering/budding.

The problem with HID lights is that they consume a lot of electricity for output, produce high operating temperatures, and produce a wider spectrum of light – much of which is not needed or used by the plants. In other words, HID lights are expensive to run, inefficient and a potential fire hazard.

That not to say that HID lights, if used properly won’t deliver great results. They most certainly will. But when you figure in the factors of cost and safety, the newly developed fluorescent grow lights as well as the most recent kid on the block, LED lights, have clear advantages.


Fluorescent lights (CFLs, Compact Fluorescent Lamps)

cfl lights indoor marijuana

125w cfl

High powered fluorescent lights are now specifically produced for indoor gardening. They are available in 2 types – Blue 6400K that emit the wavelength of light needed for plant/vegetative growth, and Red 2700K that emits the right wavelength of light for flowering growth.

To produce great crops of marijuana you’ll need both these minds of lights – more of the ‘blue’ wavelength for the first two months and then more ‘red’ when it comes to the flowering phase.

Unlike HID lights, no light falls outside of the needed spectrums which results in less waste and better growth for less power consumption.

With the development of CFL grow lights, HID lighting has been largely replaced.


LED (Light Emitting Diode) lights

best lighting for indoor cannabis growing

LED lights

The development of LED lights for growing is still in its infancy but holds the greatest promise for the future due to the huge saving in electricity costs. They’re also cooler, so you’ll have no worries about overheating your precious plants. (Although don’t think this means you can put them closer to your plants – LEDs need to be at least a foot away, which is obviously not an advantage in small spaces.)

Currently there is still debate over the preferable diode frequencies (light spectrum), best ratio of spectrum, and wattage of diodes.

Some companies say that the higher wattage per diode the better, with wattages of 2.5 to 3 being promoted – and some growers have said that they find this the most effective.

Other research has indicated that anything over 1 watt per diode means inefficiencies come into play, or in other words, you get increased power consumption for less output.

Basically, the jury’s still out on this one.

For standard LED lights, the red / blue ratio is generally 3 to 1 which is considered good for all round plant growth.

Other LED lights offer a wider range of red, blue, orange, purple and dark red, at a 6:1:1:1:1 ratio. Experiments are still on-going to determine the best ratios and colours to include.

If you’re thinking of using LEDs, do a bit more research to find the best ones for you,  bearing in mind that good quality LEDs are pretty pricey.


So what is the best lighting for indoor cannabis growing?

At the current stage of development, CFL lights still offer the best choice when considering a range of factors such as performance, power consumption, safety and upfront costs.

Using both ‘red’ and ‘blue’ spectrum CFLs will ensure fast growth and abundant flowering.

LED lights win on the power consumption front but the verdict is still out on the performance factor.

The upfront costs of LED lights is considerably higher than other types of lights but users claim that the lights will pay for themselves in time due to less electricity costs to run.

HID lights are the old standby for indoor growing gardens but due to the advancements in CFLs and LEDs, HIDs are now largely a thing of the past since the high power consumption, high heat generation and general inefficiency no longer makes them a viable option.



In short, if you’re the experimental type who likes to be on the cutting edge of technology, LED lights might be right for you – especially if you’ve got some extra coin to invest.

Otherwise you can’t go wrong with specially designed CFL grow lights. Power consumption and start-up costs are reasonable. Good performance is well documented.

Here are some links to good quality CFL lights, and also to one of the cheaper LED lights, which has been recommended by several experienced growers as a good one to start with if you want to do a very small grow under LED lighting.


UK – selection of CFL grow lights on grow light cannabis uk

click on the image to see specs, prices and availability

125-300W CFL grow lights, around £20 each



250W cfl marijuana grow light usa

USA – CFL grow light on

250 Watt CFL Grow Light 2700, from $88




LED lighting for indoor cannabis growingLED grow light –

Lighthouse Hydro BlackStar Flowering LED Grow Light, 135-watt, $179.95




A few tips on using CFL grow lights

During the vegetative phase (first two months depending on strain) the plants should be given 16 to 20 hours of light per 24 hours.

Some say you should grow your crop longer before inducing flowering as it results in a better more potent crop. But of course it depends to a degree on the strain and opinions differ even among growers of the same strains.

The length of the periods of light should be reduced to no more that 12 hours every 24 hours when shifting to flowering period (which will usually last between 8 and 11 weeks depending on strain).

The plants will continue to grow in the flowering phase and can easily double, or even triple in size.


Using UVA and UVB lights for indoor cannabis growing

“The Dutchman” grower is experimenting with using UVA and UVB lights and claims they are the best lighting for indoor cannabis growing if you want to increase the potency of your crop. For how to do this, watch the video up top.

And to get the grow lights he recommends – 4 ft Zoo MedReptiSun 10.0 UVB/UVA Bulbs –  click here:

UVA-UVB lights by Zoo Med on

UVA-UVB lights by Zoo Med on

Alright, good luck with your grow!

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