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Lighting the Whole truth


New Member
If the is not the correct place for this place. I hope is gets moved to the right place.

A few months back i began my research on growing MMJ.Being a salt water aquarist. Lighting is a major factor. So this is where a majority of my time has been spent. Searching the forums here and various other places i have never really found the answers to the question i have. But i do see alot of stress and emphasis put on watts and lumens per sq foot, for a successful grow. the area i dont see alot talk about is the color spectrum and wave length . which in my background is just as important as any. Asking around i got this emailed to me. I AM NOT THE AUTHOR OF WHAT IS POSTED BELOW !!!! Alot of the info seems valid and correct. If any one does know the source of this please let me know so the proper credit can be given.

Light for cannabis plants

Without light, cannabis plants cannot grow. In the countries in which marijuana grows best, the sun is the source of light. The amount of light and the length of the growing season in these countries results in huge tree-like cannabis plants. In most parts of North America, however, the sun is not generally intense enough for long enough periods of time to produce the same size and quality of cannabis plants that grow with ease in Latin America and other tropical countries.

Sunshine is most intense at the equator where it is closest to the earth. Some of the largest, resin-coated buds in the world grow beneath this blazing sun. So what’s this got to do with indoor growing? Plenty. Light is one of the most basic needs of all cannabis plants and the most often mismanaged.

Even the most experienced growers forget about the basic needs of a cannabis plant, especially light.

The answer to the problem of lack of sun, especially in the winter months, shortness of the growing season, and other problems is to grow indoor under simulated conditions. The rule of thumb seems to be the more light, the better.

The common incandescent light bulb emits some of the frequencies of light the cannabis plant can use, but it also emits a high percentage of far red and infra-red light which cause the cannabis plant to concentrate its growth on the stem. This results in the cannabis plant stretching toward the light bulb until it becomes so tall and spindly that it just weakly topples over.

There are several brands of bulb type. One is the incandescent cannabis plant spot light which emits higher amounts of red and blue light than the common light bulb. It is an improvement, but has it drawbacks. it is hot, for example, and cannot be placed close to the cannabis plants.

Consequently, the cannabis plant has to stretch upwards again and is in danger of becoming elongated and falling over. The red bands of light seem to encourage stem growth which is not desirable in growing marijuana. The idea is to encourage foliage growth for obvious reasons.

Flourescent light tubes range in size from one to eight feet in length so you can set up a growing area almost anywhere. There are two types of flourescent lights; standard and the wide spectrum. They can be used in conjunction with one another, but the wide spectrum lights are not sufficient on their own. The wide spectrum lights were designed as a supplementary light source and are cheaper than the standard lights.

Wide spectrum lights emit the same bands of light as the standard but the standard emit higher concentrations of red and blue bands that the cannabis plants need to grow.

The wide spectrum lights also emit infra-red, the effect of which on stem growth we have already discussed. If you are planning to grow on a large scale, you might be interested to know that the regular fluorescent lamps and fixtures, the type that are used in commercial lighting, work well when used along with the grow lights.

These commercial lights are called cool whites, and are the cheapest of the fluorescent lights we have mentioned. They emit as much blue light as the standard grow lights and the blue light is what the cannabis plants use in foliage growth.


Now we come to the question of intensity. Both the standard and wide spectrum lamps come in three intensities: regular output, high output, and very high output. You can grow a crop of cannabis plants under the regular output lamps. The difference in using the HO or VHO lamps is the time it takes to grow a crop.

Under a VHO lamp, the cannabis plants grow at a rate that is about three times the rate at which they grow under the standard lamps. People have been known to get a cannabis plant that is four feet tall in two months under one of these lights.

Under the VHO lights, one may have to raise the lights every day which means a growth rate of ate least two inches a day. The only drawback is the expense of the VHO lamps and fixtures. The VHO lamps and fixtures are almost twice the price of the standard.

Now that you have your lights up, you might be curious about the amount of light to give you cannabis plants per day. The maturation date of your cannabis plants is dependent on how much light they receive per day. The longer the dark period per day, the sooner the cannabis plant will bloom. Generally speaking, the less dark per day the better during the first six months of the cannabis plant's life.

If your cannabis plants receive 12 hours of light per day they will probably mature in 2 to 2.5 months. If they get 16 hours of light per day they will probably be blooming in 3.5 to 4 months. With 18 hours of light per day, they will flower in 4.5 to 5 months. Its a good idea to put your lights on a timer to ensure that the amount of light received each day remains constant.

Grow Light Guide

Horticultural lighting systems allow you to extend the growing season by providing your cannabis plants with an indoor equivalent to sunlight. This is a great advantage for those of you who appreciate having a year-round supply of fresh flowers, veggies and herbs. Artificial lighting is also a great way to jump-start spring by starting your seedlings months ahead of the last frost. There are three main types of horticultural lighting systems.

In summary, marijuana has a lust for light. HP sodium lamps produce 20% more light than super metal halides. Horizontal reflectors yield up to 40% more light than vertical reflectors. Hammer or pebble specular, anodized aluminum or white are the most reflective surfaces for hoods. Mirror finish is the absolute worst reflective surface for a hood. Hang 400 watt lamps at 18-24” above garden, 600 and 1000 watt lamps, 24-30” above garden. Use a light meter. Grow the strongest, healthiest cannabis plants that reach their maximum potential for resin production. Bright light brings big buds.

HID (High Intensity Discharge) Lighting

HID lighting is the most efficient way to convert electricity into light that is available to the consumer. There are two types of HID grow lights used for horticultural lighting:

HID Light Efficiency

Metal Halide - MH

Metal halide bulbs produce an abundance of light in the blue spectrum. This color of light promotes cannabis plant growth and is excellent for green leafy growth and keeping cannabis plants compact. It is the best type of light to be used as a primary light source (if no or little natural sunlight is available). The average lifespan is about 10,000 cumulative hours. The bulb will light up beyond this time but due to the gradual decline of light, it is not worth your while to wait for the bulb to finally burn out. If you compare their lumen (brightness) per unit of energy consumed, metal halides produce up to 125 lumens per watt compared to 39 lumens per watt with fluorescent lights and 18 lumens per watt for standard incandescent bulbs.

High Pressure Sodium - HPS

High pressure sodium bulbs emit an orange-red glow. This band of light triggers hormones in cannabis plants to increase flowering/budding in cannabis plants. They are the best lights available for secondary or supplemental lighting (used in conjunction with natural sunlight). This is ideal for greenhouse growing applications.

Not only is this a great flowering light, it has two features that make it a more economical choice. Their average lifespan is twice that of metal halides, but after 18,000 hours of use, they will start to draw more electricity than their rated watts while gradually producing less light. HPS bulbs are very efficient. They produce up to 140 lumens per watt. Their disadvantage is they are deficient in the blue spectrum.

If a gardener were to start a young cannabis plant under a HPS bulb, she/he would see impressive vertical growth. In fact, probably too impressive. Most cannabis plants would grow up thin and lanky and in no time you will have to prune your cannabis plant back before it grows into the light fixture. The exception to this is using a HPS light in a greenhouse. Sunlight is high in the blue spectrum which would offset any stretching caused by HPS bulbs.

Common manufacturers of metal halide and high pressure (HP) sodium lights include Philips, General Electric, Iwasaki, Venture, and Osram/Sylvania. Many of the manufacturers buy and use the same components, often manufactured by competitors. Most often the bulbs have the exact same technical statistics.

Lighting Chart - A guide for wattage per square foot.

HID Lighting Helpful Tips

Hanging height: Due to the heat that is emitted from these types of fixtures, you should hang them according to size. Smaller wattage systems (100 and 250) should be hung about 2 feet from the tops of the cannabis plants. Medium wattage systems (400 and 600) should be hung around 3 feet from the top of the cannabis plants. High wattage systems (1000 and up) should be placed at least 4 to 5 feet from the cannabis plant tops.

How long should lights run?

This depends on the type of cannabis plant. Most cannabis plants and vegetables need about 10 to 12 hours of light to promote growth. cannabis plants that produce fruits or flowers will show improvement with up to 16 hours a day of supplemental light.

Fluorescent Lighting

This type of light is perfect for starts and seedlings. They are also popular for growing low-light cannabis plants like herbs and African violets. Fluorescent lights are low intensity and need to be placed within 8" (up to 15" for shade loving cannabis plants) of the cannabis plants to be effective. They are a poor light source for flowering and budding primarily because of their low lumen output.

Incandescent Lighting

These lights are also good for starts and seedlings and provide an inexpensive alternative to HID lights, because they do not require a ballast. These lights are only good for individual cannabis plants or small groups of cannabis plants because of their low lumen output and limited range.

The Cost to Run a Lighting System

To get the operating cost per hour for a light, take the lights combined wattage, and divide it by 1000 to get the kilowatts used. Then multiply that number by the amount your electric company charges per kilowatt hour. HID lights will use the number of watts it emits per hour, ie; 600w system will use 600 watts per hour (regardless of spectrum).

How the Sunlight Effects cannabis plant Growth


Full Spectrum Fluorescents are ideal for starting seeds or cuttings or for low light cannabis plants. They are the most energy efficient grow lights available.

Although more efficient than incandescent lights, fluorescents are still much less efficient than High Intensity Discharge (HID) light systems. Larger wattage systems will cover larger areas, and since these bulbs produce greater light intensity they are superior for growing taller cannabis plants.

Metal Halide (MH) and High Pressure Sodium (HPS) are the most common HID grow lights. MH bulbs emit a blue-white spectrum, which is more conductive for vegetative growth or starting seeds and clones. HPS bulbs are red-orange in the spectrum, which is ideal for the fruiting and flowering stage of a cannabis plant’s development.

Marijuana Lighting Tips

Although natural sunlight is the best form of light for growing cannabis plants, their life cycle can be controlled more effectively with artificial lighting

The life cycle of the cannabis plant is determined by the daily photoperiod (hours of light per day).

A young cannabis plant tends to grow faster if it is grown under continuous light for the first two months of it's development.

Although the lamps should be kept as close as possible to the growing leaves, they should never be allowed to touch the cannabis plants.

The best light for cannabis plant growth emits high intensities of the blue and red bands of the light spectrum.

Fluorescent light is one of the most effective source of artificial light readily available to home growers.

Metal Halide lamps are better than most fluorescents, because they radiate more light in the blue and white bands of the light spectrum.

If your lights are too hot to touch with your hand, they are probably also too hot to be close to the growing leaves of cannabis plants.

The amount of light you supply your cannabis plants depends on the size of the garden, but at least 20 watts per square foot is recommended.

Although Metal Halide lamps are generally considered a better light source for marijuana growth, they use a lot more electricity than fluorescents..

Under artificial light, a cannabis plant can grow from three to six feet tall in three to four months.

cannabis plants entering the vegetative stage enjoy up to twenty two hours of light per day, while twelve hours or less is required for flowering.

The more light you give your cannabis plants, the faster they will grow.

Lamps should be fixed to the roof in such a way that they can easily be raised as the cannabis plant grows in height.

The use of reflectors ensures that the light is spread more uniformly around the cannabis plants.

To increase the humidity of the air in a small, enclosed garden, place a small bowl of water in the grow room.

Use a fan to cool down your cannabis plants if the lights in a small grow room raise the temperature too much.

cannabis plants grown in conditions of varying daily light patterns will not settle into a regular life cycle and will grow poorly.

If there is insufficient light in the grow room, the cannabis plants will often grow tall and thin, in search of the light.

Do not "wake up" your cannabis plants by switching on the lights if they are in the dark period of their daily light cycle.

cannabis plants grown with a long daily photoperiod, will require more frequent watering than those grown with less light.

Although incandescent, or screw-in light-bulbs are usually not suitable for good growth, they can be used in conjunction with fluorescent tubes.

If the edges of the leaves near the lights and growing tips start curling up, it usually means that they are getting too hot.

A cannabis plant will grow with as little as six hours of light per day, but requires more than twelve hours per day for good strong growth.

A cannabis plant grown with insufficient light may sometimes develop disfigured leaves with only one or two blades per leaf.

Paint the walls, floor and roof of your grow room white for better reflection of light onto your growing cannabis plants.

If you have a few cannabis plants growing unevenly under one light, you could raise the pots of the smallest cannabis plants by placing them on a few bricks.

Although easy to control, the daily light photoperiod is the single most important factor influencing the growth of your cannabis plants.

cannabis plants require less than twelve hours of light per day for at least two weeks before you can expect to see the first signs of flowers appearing.

Never increase the daily light photoperiod to more than twelve hours, once your cannabis plants have started flowering.

A cannabis plant grown indoors with lots of light will often grow larger and more potent than a similar cannabis plant growing outdoors in natural light.

To increase the amount of light available to the lower branches, you could mount extra fluorescent tubes vertically, onto the walls of your grow room.


Active Member
Very interesting read. Googling it, seems no one attributes or dates it. Too bad.

There is talk about spectrum around here, just not a lot of it. You can find some on the postingfs about LEDs. Maybe because this is an area that people really concentrate on, in latter grows, after they have the rest dialed in.



New Member
The rest of the setup is down hill after the lights. the grow room plans incluse a 4.5' x 5' area. I just need to figure out which lights that i am going to use. In my old aquarium shed i have every thing from a couple 1000 , 600 , 500 watt electronic ballast that i can use either MH or HPS. To VHO florescence and a bunch of power compact which i am really surprised that i havent seen anyone using.
From the reading i have done about lighting i think that i am going to reserve the VHO for the propagation room, keeping the mother.

Bayou tooloulo


Active Member
I'm not sure about the VHOs. Though I'm not any kind of an expert on growing or lights.

A Sylvania F48T12/D/VHO - 4 ft. - 115 Watt - T12 Linear Fluorescent Tube at 6500K, gives you 5,600 lumens. I just bought some 65watt 4200 lumen bulbs this week at Home Depot.

So at 130 watts with two of these bulbs, I can get around 50% more lumens.



New Member
Hey man, i use CFL's and they dont really have a low lumen output. Per 23w, 1750 lumens. 5 of them in a 2x1x3 closet is plenty, totalling just over 10k lumens. I agree 100% that MH and HPS will produce a better yield, but in limited space, CFL's are a godsend.


New Member
I have never used CFL. But i am a huge fan of power compacts ( pc's ) in the salt water aquarium world. i ordered a set of grow bulbs to test them out. After i finish building the room ill start the journal on the build and lighting. There are some standard choices which i am going to use as well as a few non standard ones. Unless someone here picks up on it and shares there experience . And i have alot of extra hardware that i am no longer using. Here is a pic of a 65 watt PC ( power compact ) grow bulb. One i have alot of success growing other plants with.

the color looks abit like the high end leds doesnt it ?
Bayou tooloulo


New Member
I have never even heard of these pc lights...do you by any chance know where they land in the color spectrum? And are they the same ballasts used for MH and HPS?


New Member
I have never even heard of these pc lights...do you by any chance know where they land in the color spectrum? And are they the same ballasts used for MH and HPS?
Yes the require a special ballast but it is smaller than MH and HPS.
Every aquarium shop carries them.The watting ranges from 10 - 96 and up.
Far as lumen outout goes.

Compact Fluorescent - Twin Bulb - Similar Wattage
bulb: FT36DL/835 (Dulux L) (uses T5 bulb diameter for a total width slightly wider than T12)
summary for this bulb: 11% more economical for 33% more light output at less than 1/2 the same length.
power: 36W
length: 16.6"
life: 12000 (33% worse)
av. lumens: 2494
lumens/watt: 69.3 (11.2% better)

For this CF bulb, the difference compared with T12 is that it uses 6 more watts (20% more energy) and produces 33% more light. The bulb diameter is slightly wider than a T12 (+.5") and the bulb has a shorter rated life. However, in this case, the overall bulb length is less than 1/2 as long.

Compact Fluorescent - Twin Bulb - Higher Wattage, Slightly Longer
bulb: FT55DL/835 (Dulux L) (uses T5 bulb diameter for a total width slightly wider than T12)
summary for this bulb: 20% more economical for 121% more light output at 60% of the same length.
power: 55W
length: 21.1" (still much shorter overall)
life: 12000 (33% worse)
av. lumens: 4128
lumens/watt: 75 (20.4% better)

For this CF bulb, the difference compared with T12 is that it uses 25 more watts (83.3% more energy) and produces 121% more light. The bulb diameter is slightly wider than a T12 (+.5") and the bulb has a shorter rated life. However, in this case, the overall bulb length is 60% of a 30w T12.

Compact Fluorescent - Twin Bulb - Higher Wattage, Similar Length to 30w T12
bulb: Generic 96w CF (uses T5 bulb diameter for a total width slightly wider than T12)
summary for this bulb: 20% more economical for 333% more light output at 95% of the same length.
power: 96W
length: 33.85" (still slightly shorter overall)
life: 12000 (33% worse)
av. lumens: 8100
lumens/watt: 84.4 (35.4% better)

For this CF bulb, the difference compared with T12 is that it uses 66 more watts (220% more energy) and produces 333% more light. The bulb diameter is slightly wider than T12 (+.5") and the bulb has a shorter rated life. The overall bulb length is roughly equivalent to a 30w T12 (95%).

...and just for laughs:
Double-ended Metal Halide HID
bulb: HQI-DE250/NDX
summary for this bulb: This bulb is roughly equivalent in efficiency to 9 30w T12's with 756% more light output than a single 30w T12 which it accomplishes in 6.5" of space with a lower life expectancy (but similar replacement interval).
power: 250W
length: 6.5"
life: 10000(45% worse)
av. lumens: 16000
lumens/watt: 64 (2.7% better)

For this HID bulb, the difference compared with T12 is that it uses 220 more watts (733% more energy) and produces 756% more light. The bulb size is much smaller than T12 and the bulb has a shorter rated life. The point of using this bulb is not increase lighting per area, since it produces tremendous light (and heat) in a relatively small space as compared with linear or compact fluorescents.

Here is a site that offers the grow light version. Naturallighting.com - Natural Full Spectrum Lighting[title]
one of the things i really like about these bulbs is the low profile and they dont get as hot as MH. You can also fine tune the color spectrum to stimulate growth.



New Member
Try this works great:

Feliz 250W Blue CFL Plant Growth Light Bulb - 6500K
Feliz 250W Red CFL Grow Blooming/Budding Light Bulb - 2700K
Cost: around $75.00 not including fixture (simple screw-in mogul)

Google as described for a source near to you. I use two 6500K for vegging 7mothers and am very pleased with the results. I also use one of the 125 watt for clones. The advantage I see compared to a T5 is compactness and vesatility, i.e. you can hang them vertically if you need to between plants with no heat at all. Here are the specs for the veg lite for those into it:

Feliz Model: AGRO CFL 901984
Color: 6500K Cool Full Spectrum
Lamp Base: E39 Mogul
Type: 250W Compact Fluorescent
Measurements (inches): 13.50" Height x 4.50" Width
Recommended Mounting Height: 24-30 inches from plant
Lumens: 12,000
Incandescent Equivalent: 750 Watt
Life (hours): 10,000
Voltage: 120 Volt-60Hz 2500mA
CRI: 80


New Member
Ive got some seeds currently in the germination process. i need to put them under a light until the ground and sun is capable of growing them. right now i have a 250w infrared reflector heat lamp that i found in my garage. it puts off a lot of heat, so i was thinking of putting it a ways away form the plants and making sure the temp wasnt too hot. is this alright for them, or should i just go buy a new light?


Active Member
Ive got some seeds currently in the germination process. i need to put them under a light until the ground and sun is capable of growing them. right now i have a 250w infrared reflector heat lamp that i found in my garage. it puts off a lot of heat, so i was thinking of putting it a ways away form the plants and making sure the temp wasnt too hot. is this alright for them, or should i just go buy a new light?

Buy a new light.



New Member
Thanks for the input guys, i definatly dont want to screw these up, too much $ invested already. I picked up a T10 this morning, looked for the T5 but couldnt find it in any of the stores i went to. will this do as good?
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