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How many cfls do i need

Discussion in 'Newbie Central' started by gettinggray1964, Feb 14, 2008.


    gettinggray1964 Active Member

    how many cfls do i need to grow 3 or 4 plants???:peace:

    GreenCrunchies Well-Known Member

    well i have 5 plants right now...and its not about how many, its about how many lumens they put out.
    I have 4 60 watt cfl's at 800 lumens each....i got from home depot...or wal-mart and two 105 watt lights at 6200 lumens each....there kickin ass right now, and the plants are lovin em.....

    KillHit Well-Known Member

    pictures... i have cfl too my pics are all over

    frostythesnowthug Well-Known Member

    Depends on what strain ie how tall they grow etc, and your growing technique, ie LST, SCROG/SOG..
    For example If you grew them naturally without any LST or without doing a SOG you ill need nore and more lights the taller they get, although the Lower lighting can be a slightly lower wattage bulb as its more of a supplemental for the lower branches.
    To start them off once they poke their cotyledon leaves(round leaves) out of the soil, you will get away with one CFL ith DIY reflector per plant until theyre a couple of weeks old...Then double up..Once theyre growing well i generally figure on a minimum of 4-5 per plant..
    You also need to try to keep them around 2" away from the plants for the 1st wk to avoid damaging/burning the cotyledons and first 'real' leaves., then no closer than 1" thereafter.

    You should try to get a minimum of 42w DAYLIGHT RATED (6400k) CFLs for the Veg stage(sometimes called COOL WHITE), and use 42w 2700k (warm white) CFLs for flowering.

    THChead Active Member

    Approximate light production:
    Incandescents: 17 lumens/watt
    Mercury vapor: 45-50 lumens/watt
    Fluorescents: 60-70 lumens/watt
    Metal halide: 90 lumens/watt
    High pressure sodium: 107 lumens/watt

    The minimum amount of light required by marijuana plants is around 3000 lumens per square foot. However, it's not 100% accurate, since although you may have a 10,000 lumen light, the amount of light that reaches the plant varies with the distance between the light and plants, and reflectivity of the grow box. The ideal amount is somewhere around 7000-10,000 lumens/sqft, and as long as the plants do not burn, as much light can be used as you want.
    (*note, the sun produces about 10,000 lumens/sqft, on a sunny summer day).

    THChead Active Member


    Determine the square footage of your area (example in a 4 foot by 4 foot area, there is 16 square feet)
    If you have a 1000 watt High Pressure Sodium, that produces (approx.) 107,000 lumens.
    Divide this by 16 (your square footage) 107,000 / 16 = 6687 lumens per square foot.
    So just divide the total amount of Lumens, by the total amount of Sq ft, and thats your lumens per square foot.

    slysleuth Active Member

    alright i've lurked here for a while and maybe i should be posting in the cfl subcategory, but i think my question pertains to the ops. ive got 4 23 watt cfls so around 6000 lumens for that but i also have a 24in regular flourescent light @ 13 watts t5. do the regular flourescents(t5's in particular) produce more lumens than cfls? it was more expensive than my fuckin cfl setup. also when you guys talk about grow space... are you talking about the entire area or just the area that you want the light to cover? i have like a 6x10 foot walk in closet(i use about 1/10th of it for clothes, the rest is empty) but im just using a small area to grow a few of them. what do you cfl pro's think? and also how long does a plant take to start flowering... days?! i've had my mom(god i hope its a female, i started with 2 and the other one was a male) on the 12/12 cycle for like 3 days, but its around 7-8 weeks old anyways... i had it by a window(ive got the right dedication now, i was gone). so anyways its a decently tall plant with like a total of 20 leaves(the top looks healthy, i stressed the hell out of it :( i already have 4 more in cups waiting to sprout). anyways i think i've rambled on enough.

    frostythesnowthug Well-Known Member

    If i remember correctly t5's and other tube fluoros are measured for their lumens by the inch.. But i cant remember if they generally put out more or less lumens than Cfls..I'll see if i can find the info.

    when workin out ho much lighting etc The grow area is the entire USABLE size of the cupboard cubed..

    As far as how long will it take to start flowering... that depends, some plants will show sex during veg if they are in adequate conditions and allowed to reach a decent level of maturity....Most will show within a week or two after you flip to 12/12, again depending on how good the light/ventilation etc is...IF its good theyll get their act together and flower reasonably quickly, if not they could take their time....

    If youve stressed it as bad as you say, and if it is a female, be aware that it could very likely go hermie..

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