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How To Choose The Right Indoor Marijuana Grow Lights


bc budWhat Lights to Use For Growing Weed Indoors

Growing marijuana indoors has its advantages and disadvantages just as growing the cannabis plant outside does. Indica marijuana strains are perfect for growing marijuana indoors because of their short and wide plant growth compared to the thin and tall growth of sativa marijuana strains.

When setting up a home grow location its absolutely essential that you choose the right lights at the right growing stages for your marijuana plant. Marijuana plants grow in two stages; the vegetative stage and the flowering stage.

The Vegetative Stage (A)
When a marijuana seed is first planted it enters the vegetative stage where it begins to grow out its stems to prepare for budding and the flowering stage. The vegetative stage can last anywhere from 1 week to about 40 days and requires a standard day light cycle of 18 hours on – 6 hours off for the most effective results. Some growers prefer a 24 hour light cycle for the vegetative stage, which will stimulate quicker and faster growth. Either one should work fine, however, a standard day light cycle may work better for pure Indica weed strains.

The Flowering Stage (B)
After 40 days or a couple weeks (or whenever you want to end the vegetative stage) the light cycle needs to switch to 12 hours on – 12 hours off in order to start the flowering stage, which starts as soon as you switch the light cycle allowing the plant to produce buds. When choosing when to enter the flowering stage, after about a month use good judgment based on plant size and health. For maximum growth most strains can enter the flowering stage after about 40 days as long as the plant looks healthy and is tall enough.

Keep in my mind that different weed strains combined with various growing techniques will produce different results at different times. Some strains may take longer to mature and prepare for the flowering stage compared to others. If you know the exact marijuana strain seed you have its a good idea to look up the average height when grown indoors. This will give you a perfect measurement of when your plant has matured and is ready to enter the flowering stage.

Ok, so now to the point of the article. What lights should I use for the vegetative and flowering stages?

The best lights to use for the vegetative stage would be any kind of fluorescent bulb. This is because the cannabis plant loves tons of blue light in the spectrum which can come in the form of many different fluorescent bulbs which are common for home growers in the vegetative stage because of their low height output and efficient blue hues of light. I wouldn’t recommend using high energy and heat consuming Metal Halide lights (which give off nice blue hues of light) unless you have a license to grow medical marijuana and live in a state where its legal.

When you use lights that consume a lot of electricity, you run the risk of having your energy bill draw suspicion from authorities. Luckily, there’s really no need to deal with anything other than blue hue fluorescent bulbs for indoor growing until you get to the flowering stage. This is where a High Pressure Sodium light would works best (alone or with the fluorescent lights) and you can get away with it because the lights will only be on only 12 hours a day which will consume less energy and heat.

You can see in the diagram below that the cannabis plant requires blue and white light (Metal Halide & Fluorescent lights) for the vegetative stage (A), and red, orange, and yellow light (High Pressure Sodium Bulb) for the flowering stage (B).

Light Spectrum For Growing Marijuana

marijuana cannabis light spectrum

image: howtogrowmarijuana.com


Note: Metal halide and high pressure sodium lights require a ballast for proper use and may consume a high amount of energy with high levels of heat output. A great way to save money on energy bills and to reduce heat in your grow room, consider using LED grow lights. You can find out more about LED grow lights by clicking on the banner below:

heliospectra led marijuana grow light



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  • Chris Hawkes

    Important things to consider;
    -The inverse square law
    – Sea of Green, and or Screen of Green
    – Cool tubes, allow plants to live closer to the light
    – Light on times should match daylight hours, for stealth purposes.
    – Hybrid ruderalis plants are not bound to photo period schedules (12/12), have shorter life cycles, and may be easer to grow.

    • myname the turth

      IF YOU LIKE TO GROW BIG BUDS USE 1000watts..u will get a gram per lum…

  • Timothy Titpon

    Litrogrow Lights are four foot flourescents that glow in the Dark in Blue Spectrum. They are amazing for stimulating more bud sets in Veg growth, help amazingly in Bloom cycle, & use 25 per cent the electricity of sodiums. I am NOT saying don’t use a 1,000 watt Sodium for Bloom, but use these supplemental four bank four foot T-8 light banks as supplemental. Good luck finding these beauties….maybe Commercial Grow Supply & Consignment by the Colesium in Denver. Hempy Growing!

  • bluntman

    back when I used to grow I had good results using fluoros to veg and then HPS + fluoros to flower. There is no easy answer to what light is best because of the many factors involved. Some of the most important factors include the space available and the amount of airflow/cooling another important factor is light distribution. In my experience in a wardrobe type grow space you get better results using a small HPS with fluoros to light the corners where hps light can’t reach rather than use a 1000w HPS which when surrunded by plants still won’t light up the corners but would require more cooling/airflow to avoid being a fire risk.

  • wes

    would a 250w light interfier with a main tv arial placed above it in loaft

  • Nasbils

    Would a 300 watt hps bulb hurt a 1 week
    Old seedling , 3 feet away?

    • Bark Bark DBRB


  • LukeOR

    Why not use LED grow lights?  They use less power, put off lass heat and produce only light in the spectrum’s that stimulate photosynthesis.  These wave lengths are 425, 470, 610, 630, 660 and 720.
    Metal halide and HPS light produce most of their light in the 500-600 range, this means most of the light is wasted. LED grow lights are the answer to indoor growing.  Perfect light and little heat!

    • SLAM

      hhmmm because it cost twice as much for equal wattage, to use LED.

      • no name

        Good for veg……not flowering goes out the door

  • Dianimal

    HI there, I just want to correct you on a certain point and because I hate to see people get paranoid for no reason: regarding the claim that high energy bills may draw attention from the authorities I say NO WAY IS THIS TRUE, not in the USA or UK or Western Europe anyway, and I believe the same goes for Canada, Australia, New Zealand, basically any contemporary democracy. (Leaving aside the valid debate on whether democracy really exists anywhere!) First of all, laws around data protection mean that “the authorities” cannot just go around looking at people’s energy bills to see if they are “suspicious” unless a particular person was ALREADY under surveillance. They don’t have the labour-power to do it on a large-scale and it would be illegal without probable cause. Police could not generate probable cause from energy bills because without probable cause they wouldn’t have access to them, get it? Same goes for the old myth about helicopters flying over houses with thermal imaging gear to look for possible loft-grows: the legal ability to gather data in such a way is governed by the same protocols as govern getting a search warrant to enter your premises. They can’t just “throw the net out and see what ya catch” – that is the whole point of protecting our civil liberties so we don’t live in a gestapo state. People who attempt to steal electricity, by bypassing meters or whatever other means, are the ones who get caught. This is taken much more seriously even than cultivation. I knew of a house of tweakers that got caught for electricity theft and nobody even cared about the drugs. It’s one of those things like “mail fraud” that often trips up people who are actually breaking other laws. So use metal halides or not, either cuz you want to save energy or cuz flourescents are cheaper, but don’t make your choice based on snoops watching your phone bill. Cuz if they are, then they are already on to you! xoxoxo Dianimal

    • animal

      I lived in Vancouver, Canada and one day received a phone call from the power company demanding to know why my power consumption had suddenly increased. I told them that I installed a hot tub (true) and a few days later received a visit from the local municiple sheriff. He just walked into my yard and demanded to see the hot tub. The bastard was extremely rude and when I showed him the hot tub he stormed off. He said he had probable cause to barge into my yard… NAZI prick. Anyway, don’t think it can’t happen… just saying.

      • discussting

        Sue his fucking ass

  • ericweed

    Technology is really a big help.Now they can even grow marijuana indoors….

    medicinal cannabis dispensaries

  • PatStarfish

    I really like to use a clear stream of dled grow lights to start my clones. It works well and I haven’t had any bad experiences with them.

  • So for the vegg stage its not about heat but light color?

  • Question?

    i only have blue light is it okay to just use that? and BTW thank you for the information you provided us.

  • Question?

    is it okay to use the Philips Agro 60-Watt A19 Plant Light Bulb for my new seed?

  • lee

    used a high pressure light for the vegetative and bug stage it that ok

  • hank

    YES ,why you do try to use led grow light ?

    100w led grow light can equal to 400w more HPS !!!led grow light more efficent!!save energy !!it is pefrect chocie for marijuana view the long time !!

    we are led grow light manufacture !!any inquiry led grow light , i will happy answer you !!!
    http://www.vanqled.com .eamil:vanqled7@vanqled.com skype:vanqled.com

    • Brendan Walsh

      Hank thanks for posting this been using 250watt and 600 watt for flowering and energy bill quite high , should switch to led for new crop looking forward to less worries about the heat fly bys this winter too ;0)

  • bruggeman67@charter.net

    does anyone know how much light is required for25 plants

  • tony420

    how many plants will 1 light grow? i can legally grow now. whats the best way to go about seting up a grow room???

    • Hish Hash

      A 1000 watt bulb and ballast will grow 6 plants very well. If you feed them right you should get 4oz per plant, that what I get.

  • Lousie Thomas

    Light is amongst the most significant elements in determining; exactly how much your own plant will grow and how your own buds will prove themselves worthy in the blooming stage. But Apart from lighting, there are few critical rules that the indoor marijuana growers should know about. If you like to know more about these suggestions; refer this link.

  • levia jack

    I really like this amazing blog. This blog is full of information. Lights4living

  • Alfie

    Can I use a 400w blue light all the way. And then change bulb to hps 400 when flowering. If so when best to change do I wait for it to turn under the blue light

  • dany dooby

    can I use a 75 watt energy efficient buld or should I use a 150 watt

    • Zack

      if you can afford it 150w and if it’s not 2 suspisous then yea.

  • dany dooby

    referring to the comment below how many should I use for one plant

  • Theone21

    Ok so I’m new to this and my plant is about a one an half ft tall I’m using a 200 watt ( lizard light?). About 4 and half feet above it,,, she had light stress and I think I corrected it. But Any pointers or tips about lighting ??

    • no name

      U never GEt nothing but two oz ….600watts …u be very happy…..buy a ten dollar meter that ready off ligth

    • Alden

      Hellow friend. Can i ask you. When the ligth is off the fan will be off or still open.? Tnx

    • Hish Hash

      You are losing most of the foot candles the bulb is producing at 4 feet, move it down at least 2 feet lower.

  • Alden

    Can i ask.. When the light is off the fan will be off or still open?

  • Bill Long

    CFL grow lights are a great source of light. check out advantagelightingsupply.com to purchase bulbs that will work for your plants. LED grow lights are working as well.


    I am starting in the flowering stage what kind of lights and how many watts should i use ?

    • Zack

      why not just go to walmart or something and buy cheapo bulbs like i did for my grow box.

  • Brad

    Can you provide an example of when high energy bills were the sole factor leading to an arrest? In PA I know a few people who work for the energy companies and the only give a damn if you don’t pay them. I think you shared a common delusion.

  • Tokin’ Krusty

    Hi I was wondering if it’d be possible to use 3 T8 fluorescent lights from Lowe’s that are 15 watts a piece in a closet with a fan and reflectors/mirrors? I have a plant that’s about a foot tall, definitely female. I used to have it growing outside but I live in a sketch neighborhood and don’t want any trouble. So I’m trying to grow this in my closet. Is it possible to use these lights in the veggie stage? Will I have to get stronger lights once I want it to flower? Anything helps, I am a new grower.

    • Hish Hash

      Make sure and at least use a plant/aquarium bulb, this will give you the spectrum you need. I believe phillips makes the one you need. Also a 65 watt CFL “compact fluorescent will work well, they come as part of a outdoor security light with ballast and photocell, just hard wire to a regular plug and put tape over the photocell to keep it on, then use a timer to control either 18/6 or straight 24 hour cycle.

      • professor Muir

        Best color temp for veg is 5200-5500

    • Dr. B

      The answer is yes, although I would switch to the 35 Watt T8’s in the 5000k-6400K Daylight Spectrum I use this setup for the first month of veg on babies and plants I want to keep at a slower rate of growth. You can go the whole cycle with T-8 but don’t expect large, fast or high yield plants. Best bet is to spend the 250 bucks for LED Super Veg light(s) You can run a 4×4 (or whatever) SCROG in a closet with as little as one light, 240W I have a three stage system going for my medical grow, T8’s month 1 LED month 2 and 3 then HPS for bloom with LED add on’s for extra red. Yes, I have cycled with LED only with outstanding results. Average 2-3 OZ per plant, one light per plant. Forget the mirrors, flat white paint or mylar for the closet. I got my lights at htgsupply.com The 6 Band 240w LED Vegetative Grow Light. I don’t care what anyone say’s. They work great, if it has a problem within a year (only two have gone out) HTG will give you a new one. This is my vote for your situation. Happy growing!

    • Zack

      45 watts isnt enough but id say 75 watts plus. if it’s in a grow box and you have mylar you probly could.

  • becky

    Wh at causes a seed to become so stemy?

    • Dr. B

      Genetics #1 Environment #2

    • Zack

      is it a stretched plant? cause i remember seeing that if it stretches then you need to get rid of it.

  • Brendan Walsh

    For the veg stage what led light do you use and also for flower stage ?

  • lucky

    Hi i was wondering if i can start my flowering stage with 2000 watts and add 1000 more will this hert?

    • Zack

      isnt even 2k watts suspisous? i wouldnt use 800 for mine total

  • Easy

    I am bringing 4 plants indoors that have nice buds. What simple bulbs and how many do I need 2 put them in my closet?

    • Zack

      i’m on a low budget so i would say CFL 100w or 150w 3000k to 3400k for flowering i think but it could be different. i just know t5 tubes are 3000k.. i do have cfls for my grow box but i’m too tired to go look.

  • nas

    I had bud my plants useing cfl 100w bulbs 10 each and the buds does not have any strength. Can the light be a problem it looks great. But no smell and strenght i need help please.

    • professor Muir

      Check the ph of the soil first and make sure it is around 6.5. If that is good check nutrient content and maybe flush if to high. Then water less marijuana likes it dry and if it is a sativa it will take longer

    • MrMcFreely

      How far do you have the lights from the plants? Floros need to be real close to be affective since they are not as intense as HID’s. Make sure your lumen/sq ft ratio is good. 3000 per is bare minimum. 5000-8000 is better.

    • Zack

      mylar and as he said close to plants but measure to 4-1/2 -5 or 6 inches away so you dont burn the plant.

    • Rob

      How did you determine it was time to harvest? Were you watchimg the trichomes? Or, were you doing something else?

  • allin green

    agro lite xt..the bomb light for colors, lumens & yield!! also useable for not only 16/8 but also for 12/12. my favorite pick!!!

  • Zack

    i would just use hydrofarm t5 6500k and then agromax 3000k nevermind buying another light… i cant afford that. i dont work for many reasons and i’m on disability and the fact i use cannabis for insane joint pain and i will never take pain pills cause i know this is the best for my condition and as said it’s safe. my family isnt as supportive of this as i… they live by false information and never will wake up and smell the coffee. it’s stupid that i hear bs from brother especially.. just said from information from the government that it causes heart attacks but ive never had one in all the years ive smoked it so thats just bs. at the moment i’m out of smoke and i will probly not get any till around christmas and hell i’ll be in alot of pain then and probly in a week or 2 it willl just creep in with a punch.. jeeze!!

    • phrank

      Check out kratom. Non opioid opioid receptor agonist, legal, non addictive(well, sort of), and will help your pain and get you moving. Kratom and kanna kept me from losing my mind as I stopped smoking after geting busted. Don’t suggest kanna its a little risky for some, but kratom rocks. Kratomherbs or kratomnaturals. I don’t like tea, so I use uei. Many extracts are junk.

      • mary

        ok holyer than thou..ok you got caught…you made mistakes..get off here…what you got caught and now your holy…leave real people to medicate there pains with what god gave us..natural medication…natural…

        • phrank

          I’m not sure what you’re taking that you imagine me acting or being “holy”, but its all in YOUR head. Kratom and kanna are BOTH natural plant substances, go do YOUR preaching somewhere else, leghair. And yup, I got caught, but I was as good as any grower in the country, and have solid advice to offer. If you had a brain you’d listen instead o bitchin, these kids are wasting time and effort, apparently without ever reading so much as a high times q and a section. Go grow under a 75w equivelent cfl, dumbass, I won’t waste any more time here.

          • FunkyBrains

            I might as well join in the fun here. Phrank is totally off base and clearly has no actual grow knowledge of using cfl. Maybe it’s just been a while since he grew, like back in the 70’s or maybe he just doesn’t grasp certain concepts. Truth be told, more small lights actually DOES do more good than one large one. Simply put 1 lumen is one lumen. I have had a few successful grows over my time utilizing only low wattage cfl’s. I’m talking big fat juicy quality, its all in how you present it. Just read up and go for it.

  • phrank

    Wow, just wow. Lots of bad ideas here. I got busted years ago and can’t play anymore, but ill fill you in on some good knowledge. First, a whole bunch of weak lights do not equal one bright light. 10 weak cfls at 100w(assuming you mean 100w equivelent) each for flowering is crap, you’re wasting time and energy and giving bad advice. There are much better standard output t5 tube fixtures and 300w equivelent cfls(4000lumens each at 3000k) available if you can’t use a hps lamp. 10 100w cfls use roughly 150w, buy a 150 w hps and stop wasting time(and don’t try more than one or 2 under it). The whole fixture and bulb won’t cost much more than quarter bag of dank, and you ont ever get any dank at all with low watt cfls. Lastly, unless your state is legal, stop seeking advice on line, buy a book, and visit a hydroponic store for some literature. Big brother IS watching you. I won’t lie, I miss it, but a whole night of questioning, watching your love get hauled out in evidence bags, the expense and limitations from court proceedings and probation, al make you feel pretty stupid when you’re caught. Lay low, shut up your bragging, and don’t solicite criminal advice online.

  • Mark

    Still spend $1499.00 for a full spectrum 255w ??? VANQ will tell you how you pay less money, at the same time , enjoy more newest technology of led growing . VANQ latest full spectrum(380-780nm) COB 300w led grow light. the earliest full spectrum led grow light for medical growing . http://www.vanqled.com Skype: vanqled12 email: vanqled12@vanqled.com

    • Den of Earth

      Those lights are 1 watt LED lights. The sweet spot for growing plants are grow arrays using 3 Watt LEDs.

      • Mark

        they are COB 72w grow arrays. consist of 72pcs 1 watt on one array. with phosphors full spectrum.

        • Den of Earth

          You won’t get much depth penetration of light through the canopy with 1 watts led arrays. You need 3w led arrays to get the depth penetration for decent flowering. Those lights you are pushing are over priced junk.

          • Tang Mark

            Well , let’s say people hobby difference . We have one customer in Holland , professional grow shop seeking for a totally great led grow light for marijuana, i know it’s also growers looking for . it’s a super large market . before that he has test many led grow lights, but no would be satisfied.
            this time, he prepared a fully perfect test condition,many testing machines import from US, Germany ,China ,and do the test in Vienna Austria with 300W 7band from May to July , more than three month passed , the outcomes seems sweet . what his one words impressed me most is “none of this LED could beat a 300W Vanqled”, this is his original words. I really appreciate all the awesome work my buddy has done for the testing . after that , he will do very aggressive promotion in the Whole Europe.

          • alf Jahag

            Listen you silly little girl, those 1w diodes are barely 2mm together they are on 1 big diode, and it’s all packed together under 1 optic lense, not some big lumbersome peice of plastic. So what is better? 3w diodes placed half inch apart or dozens of 1w placed onto a diode only 2 inches square?. Think about it next time den comes back down to earth..

    • Eggy

      Exactly mate, dizzy fools still rocking foot long panels with infinitely doubtful performance, when they could have all that power and penetration in 1 big super powerful diode. Vanq bitches van rucking Q..

    • Tang Mark

      and now 600W(4X150W) COB LED Grow light available , full spectrum 380-840nm imitate the sunlight. super intensity and high lumen which would solve the problem now usual grow lights facing.
      80lm/w , actual power more than 572.76W , all those main data most manufacturer can not achieve. i believe it’s a revolution for modern growing ….

  • ZackDaddy

    hi im growing my own strain of marijuana and am currntly using an LED lamp called desk-brite to grow during the vegetation stage and was wondering if i need brighter lights or higher watts for my lights just for veg. stage. please help me i cant find this anywhere on the internet also i’d like to know how much watts are in these desk-brite lamps?

  • alf Jahag

    Fucking A, VANQ my friends VAN fucking Q. They do a 75w full spectrum 380-840 nm phosphor LED for only £20, and a 100w for £29, power supplies are cheap as shit of ebay auction and buck boost to help precisely control voltage and current are also peanuts. It cost me £50 for 2x their 72w 7-spectrum chips and only £33 for a 100w version including power supply and regulators, so that’s £80 for 240 actual watts of LED power, add an optic lense and your rocking dense buds. Fuck kessil, bysen, hydro grow and the rest of them capitalist rip-off sellers who charge £250 for barely 200w of power on a peice of plastic over 1 foot long, this is why growers still doubt LED effectiveness. You can have all that power in a diode barely 2 inches square, vanq bitches check em out on aliexpress, especially their ground breaking full spectrum 380-840 phosphor.. do iT..

  • alf Jahag

    Yes vanq on aliexpress sell very high PAR chips with multiple 1w LED’s in a matrix barely 2 inches square, the penetration is sick, and the price sells itself, around £25 for 72w chip and £33 for 100w, they have 7-band (660,630,440,470,600,380,730). Not those doubtable big-arsed plastic panels that Look cheap and fail if 1 diode dies and takes the whole unit with it.. Bysen charge over $1000 for their full spectrum 380-850 nm chip, but vanq sell it much much cheaper.. Sound good then type VANQ led into Google and see for yourself.. Vanq ladies van bloody Q..

    • Tang Mark

      you awesome guy know the key for the grow leds. appreciate….

  • JoeGrow

    Cool White fluorescent bulbs are full spectrum.

  • anonymous

    i just need more money my job pays me shit. what is the cheapest way to grow a few plants in my closest without all this technical crap?