Ideal Lighting For Marijuana Growth

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Ideal Lighting For Marijuana Growth

Post by Weedguru Higher » Tue Nov 08, 2005 5:50 pm

Ideal Lighting For Marijuana Growth
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Light is needed by a plant for using nutrients and manufacturing food. It has a great influence on chlorophyll production, growth rate, leaf size, and flower and seed production. Light will be one of the most important aspects of your grow operation.

For the purposes of growing pot there are two basic types of lights: Fluorescent's and High Intensity Discharge (HID)

What Type of Grow Light Should I use?


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.

HID vs. Fluorescents

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The main difference is that fluorescent's create light by passing electricity through a gas vapor under low pressure and HID creates light by passing electricity through a gas vapor under high pressure. HID lights are MUCH brighter and while initially more expensive, are more cost efficient to operate and will grow a much nicer crop. Therefore, they are the light of choice for most indoor growers.

High Intensity Discharge (HID)


Indoors, 2000 lumens per sq. ft. is about as low as you want to go indoors. If you get under this mark, plant growth will certainly not go as fast as possible, and internode/stem length will increase. Also, light distance to plants will be much more critical. Daily adjustments to the lamps will be necessary, meaning you get no vacations. 2500 lumens psf should be a good target, and 3000 is optimal if your going to inject or enrich CO2 levels (more on that later). High Intensity Discharge lamps are the best solution for most indoor growers.


HID lamps come in 3 basic flavors: High Pressure Sodium (HPS), Metal Halide (MH) and Mercury Vapor. Metal Halide is an improved spectrum, higher intensity Mercury Vapor design. HPS is a yellowish sort of light, maybe a bit pink or orange. Same as some street lamps. HPS lamps can be used to grow a crop from start to finish. Tests show that the HPS crop will mature 1 week later than a similar crop under MH, but it will be a bigger yield, so it's better to wait the extra week.

A lighting ballast is necessary to operate discharge lights because they have negative resistance, meaning they are unable to regulate the amount of current that passes through them. A lighting ballast must be used to control current flow; otherwise the light could fail. Small light sources can use passive components, which require no additional power to operate, as ballasts.

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Ballast

The easiest HID to buy, and least expensive initially are the fluorescent and mercury vapor lamps. MV will put out about 8000 lumens per 175 watts, and 150 watts of HPS puts out about 15k lumens, so HPS is almost twice as efficient. But the color spectrum from MV lamp output is not as good. HPS is high in reds, which works well for flowering, while the Metal Halide is rich in blues, needed for the best vegetative growth. Unfortunately, MV lamps provide the worst spectrum for plant growth, but are very inexpensive to purchase. They are not recommended, unless you find them free, and even then, the electricity/efficiency issues outweigh the initial costs saved. 400 watt HPS will output around 45k lumens.

For every 500 watts of continuous use, you use about $20 a month in electricity, so it is evident that a lamp taking half the power to output the same lumens (or twice the lumens at the same power level) will pay for itself in a year or so, and from then on, continuous savings will be reaped. This is a simple initial cost vs. operating costs calculation, and does not take into account the faster growth and increased yield the HPS lamp will give you, due to more light being available. If this is factored into the calculation the HPS lamp will pay for itself with the first crop, when compared to MV or fluorescent lamps, since it is easily twice as efficient and grows flowers faster and bigger.

Lamp Type--------Watts------ Lumens/bulb - Total efficiency
Fluorescent Bulb---40--------------3000-------------30k lumens
Mercury Vapor----175-------------8000--------------20k lumens
Metal Halide-------400-------------36000------------36k lumens
High P. Sodium---400-------------45000-------------45k lumens

Notice the Mercury Vapor lamps are less efficient than the fluorescent (FL), and can not be positioned as close to the plants, so the plants will not be able to use as much of the MV light. The light distribution is not as good either. MV lamps simply are not suitable for indoor gardening.

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HPS Light and Metal Halide Light

Use fluorescent, MH, or HPS lamps only. Halogen arc lamps generate too much heat and not very much light for the wattage they use, and are also not recommenced, even though the light spectrum is suitable for decent growth. There is a new type of HPS lamp called Son Agro, and it is available in a 250, 1000, and 400 watt range. The 400 is actually 430 watts; they have added 30 watts of blue to this bulb. It is a very bright lamp (53k lumens) and is made for greenhouse use. These bulbs can be purchased to replace normal HPS bulbs, so they are an option if you already own a HPS lamp. The beauty of this bulb is that you do not give up most of the advantages of MH lamps, such as minimal internode spacing and early maturation, like most HPS users do, and you have all advantages of a HPS lamp.One bulb does it all.

Internodal length of plants grown with the Son Agro are the shortest ever seen with any type of lamp. Plants grown under this lamp are incredibly bushy, compact and grow very fast. Son Agro bulbs however, do not last as long as normal HPS bulbs. There is something like a 25% difference in bulb life. Metal Halide (MH) is another option, and is available in both a 36k and 40k lumen bulbs for the 400 watt size. The Super Bulb (40k) is about $10-15 more, and provides an extra 4000 lumens. I think the Super Bulb may last longer; if so, that makes it the way to go. Halide light is more blue and better than straight HPS for vegetative growth, but is much less efficient than HPS.

It is possible to purchase conversion bulbs for a MH lamp that convert it to HPS, but the cost of the conversion bulb is more expensive than the color corrected Son Agro bulb, so I would recommend just buying the Son Agro HPS. Even though it costs more initially, you get more for your energy dollar later, and it's much easier to hang than 10 fluorescent tubes. If you have a MH 36k lumen lamp burning at 400 watts and a 53k lumen HPS burning at 430 watts, which is better efficiency wise? Which will provide a better yield? Obviously, the Son Agro HPS, but of course, the initial cost is higher. Actually, the ballast will add about 10% to these wattage numbers. The Son Agro bulb will prove much better than the MH for any purpose.

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Sun Agro 430Watt

The MH bulb does not last as long, but is cheaper. Compare $36 for a 400 watt MH bulb vs. $40 for the HPS bulb. Add $15 for the Son Agro HPS. The HPS bulb life is twice as long. 10k hours vs. 21k hours. The Son Agro is 16k hours or so. Still, longer bulb life and more light add up to more for your energy dollar long term. Horizontal mounting of any HID is a good idea, as this will boost by 30% the amount of light that actually reaches the plants. Most HID's sold for indoor garden use these days are of this horizontal mounting arrangement.

HPS is much less expensive to operate than any other type of lamp, but comes in the 70 watt size at the home improvement stores. This size is not very efficient, but blows away FL in efficiency, so they might be an alternative to FL for very small operations, like 9 sq. feet or less. Over 9 sqr. feet, you need more light than one of these lamps can provide, but you could use two of them. 70 watt HPS lamps cost about $40 each, complete. Two lamps would be 140 watts putting out about 12k lumens, so it's better than FL, but a 150 watt HPS puts out about 18k lumens, the bulb life is longer, bulbs are cheaper and the lamp more efficient to operate.

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70 Watt HPS

The biggest problem is that the mid size lamps like the 150 and 250 watt HPS are almost as expensive to buy as the larger 400's. For this reason, if you have room for the larger lamp, buy the 400. If your going pro, a 1080 watt model is available too, but you might find there is better light distribution from two 400's rather than one large lamp. Of course, the two smaller lamps are more expensive to purchase than one large lamp, so most people choose the larger lamp for bigger operations. Heat buildup in the room is a factor with HID lamps, and just how much light the plants can use is determined by temperature, CO2 levels, nutrient availability, PH, and other factors. Too big of a lamp for a space will make constant venting necessary, and then there is no way to enrich CO2, since it's getting blown out of the room right away.

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Fluorescents

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Fluorescents come in a wide variety of shapes and sizes. There are compacts, twist bulbs and circle bulbs. They all work the same way. They have a starter and ballast which help provide a steady and regulated amount of electricity to the light. Before HID lights were available indoor growers used fluorescent lights. While fluorescents can be used for an entire grow from seedling to harvest, it is generally not advised to use them in this way. To grow effectively with fluorescent's, think small. These lights are better suited for starting seedlings, rooting clones and small plants, maintaining moms for cloning purposes, and providing sidelight for the undergrowth. These situations do not require a high intensity of light to run their course. The light emitted by fluorescents is gentler and more diffuse, it doesn't release a lot of heat, and doesn't make the plant work as hard. For this reason they can be kept closer to the plant. One or two inches is sufficient, but this also means that the lights must be adjusted almost daily to accommodate growth which can be troublesome.

Lighting No-No's

Don't burn your plants by getting them to close to the light(s). Fluorescent's do not put out much heat and can be as close as one or two inches. HID lights get much hotter and will need to be farther away. A good test is to put your hand between the light and the plant. If your hand gets too hot for comfort, the light is too close.

There are some common lights that may induce a seed to come up, but are worthless for growing purposes. These lights include; Any incandescent (regular) light bulb, halogen lights, black lights and heat lamps. Don't waste your time trying to grow with these lights, you will only be disappointed.

compiled using this article
http://www.concept420.com/marijuana_lighting.htm


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Post by Dr. Greenthumb » Wed Feb 22, 2006 2:40 am

thanks to the overgrow FAQ and whoever help put this info together and higher for posting it up here
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Post by stonedsoulja » Sun Oct 29, 2006 2:08 pm

You forgot natural light!! :P

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Post by Ninelives » Sat Feb 03, 2007 9:47 pm

stonedsoulja wrote:You forgot natural light!! :P
Right...No better light then the sun, I have a 1000 watt HPS light,but I now longer use it, Our flowering cabinet is to small,causeing the plants to bleach out.


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lighting

Post by osirus15 » Mon Apr 02, 2007 7:47 am

so should i get like 2 150 watt fluorecents for 1 plant or would 1 be fine???

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Re: lighting

Post by danthebadman » Tue Apr 03, 2007 3:24 pm

osirus15 wrote:so should i get like 2 150 watt fluorecents for 1 plant or would 1 be fine???
i would get 2...one white spec and 1 red spec...mixing spectrum's will help the plants flowering growth

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Re: Lighting for marijuana growth

Post by Weedguru Higher » Wed Mar 03, 2010 5:00 pm

This guide has been updated
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Re: Lighting for marijuana growth

Post by SpRi7e » Wed Mar 03, 2010 11:28 pm

I think you should also put in there for the HID lights need a ballast to work, and when setting them up, the HPS light needs an igniter for them to work. The costs of those parts (the ballast is about 5x more than the light itself) compared to a CFL grow setup can also play a huge roll in which light to use and depending on if the cooling is good enough for a HPS/MH light to be operating in.
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Re: Lighting for marijuana growth

Post by Weedguru Higher » Thu Mar 04, 2010 12:06 am

(Y) Thanks

I copied and pasted that.
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