Marijuana Grow Lights

Light = Weight

About Marijuana Grow Lights

Marijuana Grow Lights are one of the most important ingredients to achieve good grow results. The more light, the more weight your harvest will have.

When you grow cannabis, you will put your plants initially under 18 hours of light. For the remaining 6 hours they need total darkness.

Grow Lights

This 18/6 hours period is called “vegetative stage”. The plant thinks it is spring. It puts its energy into leaf and stem growth. It will not develop buds.

After 2 – 4 weeks of vegetative growth, you are going to switch the light to 12 hours on / 12 hours off. This will make the plant think that it has become middle/late summer. Time to develop buds!

If you have decided to use different light bulbs for vegetative / flowering stage, now is the time to change them.

If you want to avoid stress for your green friends, don’t switch the light radical from 18 hours on to 12 hours. Go 2 or 3 days with 16 hours / 8 hours and 14/10.

The switching of the lights is done by a timer. Not manually. Because otherwise one is likely to forget about it.

Light Color

As mentioned earlier, diferrent light bulbs have diferrent colors.

Plants in vegetation mode need more blue light. MH Lights provide that. MH lights even deliver some red light which makes it possible to use them over the whole plant life.

Flowering plants need more red light, as supplied by HPS lights.

The CFL Lamps are available in red, blue and mixed colors.

Light Color (also called light temperature) is described in Kelvin. 2700 K is a very red spectrum for flowering. 6400 K is a cool blue/green light, as needed for growth. There is also 14.000 K available which has even more blue.

Light Color Temperature Table

Used for Kelvin Color Name Color
Growing around 6400 Daylight, Cool blueish
Flowering around 2700 Warm yellowish – redish

3 Types of Lamps

There are High Pressure Lamps, Compact Flouro Lamps and LED Lights available. They all have their strength and weaknesses.

High Pressure Lamps

These are the (still) most commonly used Lamps.

Their brightness and good light color bring great results as Marijuana Grow Lights.

However, they also use a lot of Energy (200 – 600 Watt) and produce a lot of heat. Strong ventilation systems are needed. High Pressure bulbs also need a balast to start them up.

High Pressure Sodium Lights (HPS).

Marijuana Grow Lights

High Pressure Sodium Lights emit an orange/red light. Cannabis needs this during the flowering stage.

Do not use HPS during the vegetative stages of your plants growth.

These Bulbs have a lifespan of ca. 24.000 hours.

High Power Grow lights

Metal Halide Lights (MH).

Marijuana Grow Lights

They send out light in the blue spectrum, which is used in the vegetative (growth) stage of plants.

These bulbs also emit some red. Therefore they can be used for flowering, too. They will yield a good harvest. These bulbs are the best option when you decide to grow under high pressure bulbs.

One disadvantage of MH Lights is their relatively short lifespan of only 10.000 hours.

Compact Fluorescent Lamps (CFL)

Marijuana Grow Lights

A very inexpensive but good option is the use of Compact Fluorescent Lamps (CFL). As shown on the left.

The bulbs are fairly cheap. They do not need a ballast. They run relatively cold

One Lamp with at least 100 Watt will be enough for 1-2 plants. Better use 2 CFLs.

They are available in diferrent colors for vegetative (6400K) and flowering stage (2700K). I had success even with using only one flowering bulb for the whole plant life.

Compact Fluorescent Grow Lights

LED Lights

Marijuana LED Lights

… are an interesting new alternative. They use only very little energy, develop not much heat and have a long lifespan of ca. 50-100.000 hours.

Currently (2012), many people seem to use them. There are plenty of Videos about them on YouTube.

The development has been going very fast. Right now it is actually possible to have fantastic results with LED Grow Lamps. Please read this page: A great Marijuana LED Grow Light

There are also big quality diferrences in the LEDs. Low quality ones will burn out quickly and don’t deliver enough light anymore.

LED Marijuana Grow Lights work well for the vegetative stadium. But if used for flowering, it is recommended to use at least 60 watt per plant.

LED Grow Lights emit a light that is Red + Blue. It is purple to the eyes.

Marijuana Grow Lights

Always use a reflector (except with LED lights) for more efficiency with your Marijuana Grow Lights. Very recommended.


Beginners with a small Budget choose Compact Flouro Lights as Marijuana Grow Lights. They are cheap and don’t throw much heat. If you can, buy a blue one (6400K) for veggie stage and a red one for flowering stage. Only one red one (2700K) for the whole plant life will do, too.

High pressure grow light will bring bigger results. You can use either one MH Light for the whole plant life, or one MH for the veggie phase and 1 HPS for the flowering phase. You will need ventilation to get rid of the heat. But the increased yield is definitely worth the effort,

LED Lights are worth testing because of their very low energy consumtion, low heat and long life. They are currently (2010) quite pricey. I recommend them for the veggie phase, maybe in combination with CFLs.

We highly recommend these newly developed High Efficient LED Grow Lights

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