Marijuana Lighting

Marijuana needs light to grow. For outdoor growers, this is supplied by the sun but indoor growers need to replicate the sun in their grow room using marijuana grow lights.

In this topic you should come out with an understanding of the terms used in lighting, the types of marijuana lighting available for your marijuana grow room, and the light cycles you will need for the different stages of your marijuana plants life cycle.

Lighting Basics Explained – What are the terms used in lighting?

Lumens and Kelvin
The main terms used when people refer to light in marijuana growing are lumens and kelvin, which are the brightness and warmth of light. Lumens are a measurement of the total amount of visible light and Kelvin is a measure of the colour temperature the bulb is emitting. Light is comprised of separate bands of colours, with each colour sending the plant a different signal and promoting different types of growth. These contrasting color signals mean you require different marijuana grow lights throughout the various stages of your grow.Light Spectrum Table

Vegetative growth
You need a bulb that emits light from the blue end of the spectrum as it imitates the midday sun of summer. The recommended light will be 6500k.

When flowering your plant, you will need a bulb that imitates a similar light of Fall/Autumn, which is towards the red end of the spectrum. A bulb that is 2700k will be suitable for flowering.

Brilliance is used to discuss the clarity and the sharpness of the light as it gets further away from the source, or in this case, the bulb. As you get further away from the light source, its brilliance deteriorates. This affects how far away you keep the plant from your marijuana grow lights:: too far away and you’ll stretch and weaken your plants; too close and you’ll burn and damage them.

The wattage you use affects the amount of space your light will cover; the higher the wattage, the larger the surface area covered. For example, a 1000 watt bulb lights a larger surface area than a 600 watt bulb. The type of light you are using and the amount of space you are growing in will affect the amount of wattage you will need.

What types of marijuana lighting and equipment are available?

This section will explain the different lighting options available, how to use them, as well as very basic pros and cons.

Fluorescent Tubes

What are they?Fluorescent tube
Fluorescent tubes are long glass tubes filled with inert gasses. They come in a selection of lengths and are available in a variety of different color spectrums, emulating the spectrums found in sunlight. Most growers use fluorescent tubes on clones and to maintain mother plants. They can be used for flowering, but the buds and yield will be poor, making it not worth your while. Also, the light brilliance from fluorescent tubes degrades rapidly.

Best practice:
To get the most out of fluorescent tubes, you will need to keep them 6-8 inches away from your plant. They are good for use on clones and seedlings or for vegetative growth. Try to avoid using them for flowering.

$80 for T5 Grow light 2 Tube – $220 for T5 Grow light 8 Tube.

20,000 hours.

-Excellent for seedling and clone growth.
-Low Running Cost.

-Not good for flowering.
-Bad light penetration.


What are they?CFL bulb
Compact fluorescent lights or CFLs are similar to standard fluorescent tubes, but are smaller in size and boast increased power. They are available in both daylight (6500k) and warm/soft light (2700k) and generate very little heat so are ideal for smaller grow spaces.

Best practice advice:
If you’re using CFL’s as your weed grow lights, you are better using more, lower wattage bulbs to spread the light around the plant. You will need to keep CFLs close to your plant as they a have poor light brilliance. Increase your light coverage and penetration by hanging lights around the side of the plant.

20,000 hours

What are the Costs?
$40 for a 100watt bulb.

-Good for small grow spaces.
-Low running cost.
-Do not require ballast.
-You can get them from home depot.

-Not suitable for larger grows.
-Lack penetrative power so need to be kept close.

LED Grow Lighting

What are they? LED Grow Lights
Unlike HID lights LED lamps contain no filament to burn out and therefore have an extremely long lifetime, making them an ideal hydroponic lighting choice. For many, LED lighting is seen as the future of indoor growing as it has extremely efficient running costs that are a fraction of HID and CFL lights while generating very little heat.

Best practice advice:
LED grow lighting runs at a very low heat, meaning you can grow your plants right up to the light without overly worrying about heat burn.

60,000 hours

What are the costs?
$900-$1000 dollars for 400watt HID equivalent.

-Extremely efficient.
-Lamps are at a fixed angle so all light is directed at the plants.
-Run at low temperatures.
-Long life.

-Extremely expensive initial cost.
-Currently do not produce the same quality weed as a HID marijuana lighting set up.


What are they?
HID or High Intensity Discharge lamps are the most common type of marijuana grow lights used for indoor growing and are arguably the most efficient way of producing good yields indoors. The HID family includes, Metal Halide (MH) and High Pressure Sodium (HPS). HID lamps produce the perfect spectrum for both the vegetative and flowering stages of marijuana growth.


What are they?Metal halide bulb
MH or Metal Halide are currently the most efficient source of artificial white light available to indoor marijuana growers for vegetative growth. MH bulbs come in a range of watt sizes, including; 175, 250, 400, 600, 1000 and 1100. The most popular with indoor growers are the 400 – 600 watts.

Best practice advice:
A metal halide bulb’s light spectrum and 6500 Kelvin temperature are perfect for the vegetative growth stage of your marijuana plant. MH bulbs have excellent light brilliance, but produce a lot of heat.

10,000 hours.


What are they?High pressure sodium bulb
HPS or High Pressure Sodium is an extremely efficient bulb that emits an orange light spectrum, mimicing the sun of fall/autumn (2700K). Like MH bulbs, HPS come in a range of watt sizes. The most popular with indoor growers are the 600 watts.

Best practice advice:
To get the best out of your HPS bulbs, use for the flowering stage of your plants life cylcle in conjunction with a MH bulb, with the most efficient ratio being 1 HPS for every 1 MH.

10,000 hours.

What are the costs?
Average Cost incl. ballast (need to have specific costs inserted)
400 watt MH lamp – $85 – $120.
400 watt HPS $25 -$40.
400 watt Ballast $175.

-Excellent marijuana lighting for bud production.
-Excellent Spectrum.
-Still the best light sources for indoor grow.

-High electricity bill.
-Run at a high heat.
-Short life in comparison to others.

A guide to maximising your marijuana grow lights using specialist reflection equipment:

Reflector HoodsReflector hood
Reflector hoods make your bulb more efficient as they reflect light back towards the plant. An effective horizontal reflector hood increases the amount of light coverage and brilliance your weed grow lights produce, helping to produce bigger yields. The closer you move the hood to your bulb, the more light it will reflect. This in turn generates more heat which growers need to be careful of as it can cause your plant to suffer from heat burn. . Open ended hoods dissipate heat quicker as do those made from aluminium. To increase cooling, aim a fan at the light hood to circulate air around the bulb.

Grow Room Reflection
Using reflection helps get light to the lower parts of the plant, increasing your overall bud production and making your grow room more efficient. There are many different types of reflective materials available for your grow room with the best two listed below. For more examples, please view the Grow Room section.
Mylar reflective material
Mylar – Is the preferred reflector of choice for most indoor growers as it reflects almost all light from your marijuana lighting when laid flat against the wall. Cover staple or nails with tape to prevent ripping.Flat white paint

Flat White Paint – Contains little or no light-absorbing pigment and therefore reflects large amount of light. Use a matt texture as it reflects more light.

What is ballast?
Ballast for marijuana lightsBallast is used in conjunction with a HID lighting set up. Ballast is a transformer that alters the electrical current used by your bulb. A smart grower will buy their entire HID system at the same time, including, lamp, ballast, socket, connecting wiring and timer. If you do not match the ballast with the bulb, you either run the risk of having inefficient lighting or a burn out, which could result in you losing more than your marijuana crop! Ballasts run between 90 – 150°F, so make sure they are not placed on anything flammable.

Bulb Proximity
Plants need around 10,000 lumens for maximum growth and yield. The table below will tell you how far you should be keeping your light bulbs above the plant.
Grow light proximity table

Light Cycles
A light cycle is the amount of light and darkness within a 24 hour period. Throughout its life, your marijuana plant will require different amounts of light depending on what growth stage it has reached. Having your plant on the correct light cycle is important if you’re going to grow good quality weed. Putting your plant on the wrong cycle can put it under stress resulting in a hermaphrodite plant and small amounts of weak marijuana.
You can use the following table to see what light cycles you should be on for the various stages of your marijuana plants life cycle, to help ensure you’re getting the most out of your marijuana grow lights.Marijuana light cycles

Selecting the right marijuana lighting can be a daunting task when setting up your grow room. The information above on marijuana grow lights and hydroponic lighting should provide all the info you need to help grow some sticky green buds.

47 comments on Marijuana Lighting
  1. Green Man

    The usual rule with 600w light coverage is to have around 1 light per 10 square foot.

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  2. Jay

    How many 600 watt Hid lights do you think I need for a 600 square foot vegetative growth room, 8 foot tall ceiling with reflective celling and walls?

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    Rating: +1 (from 3 votes)
  3. Ryan

    Galaxyhydro 300w is one of my favourite. First of all, it fits every budget.. then it is full spectrum, 50k hours life, 2 years warranty … so I find this light really perfect for my requirements.

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    Rating: +5 (from 11 votes)
  4. Allainyaha Charlene Marie Matthews

    Seed germination seems to be the easier part of the growing process
    , Using the paper towel method. I placed two seeds in a plastic bag, vented, placed under my pillow to keep warm, both seeds sprouted in two days.

    Keeoing my finger cross I hope the plant grows????

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  5. Teddy Takchy

    I would like to ask.. is it enough a Full Spectrum Double Chips LED 800 W (59 pieces Red, 12 pieces Blue, 4 pieces yellow, 4 pieces Warm white, 1 piece UV & 1 piece IR) For 6 plants ? Am using foldable folding aluminium ( Mylar) with 2 vents.. and a pH water in range 6.0 to 7.0 in a Black Fabric Pot, Light Cycle ( 18/6 Vegetative ; 12/12 Flowering ) ? The LED has 2 fans built in and I’m using 2 oscillating fans separately .. my grow space is 160 x 90 cm , Height 270 cm. What do you think Guys? PLEASE REPLY

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  6. Davon

    I was wondering…Since this is telling me about how many hours indoor growing will need along with how much light and darkness…I was wondering if you could tell me how long for outdoor growing…like when it enters seedling stage can I keep the plant out for this many hours for light and bring it in for how ever many hours for darkness or keep it outside at night then bring it in for lighting…im a beginner and I need a lot of tips and guide lines for my first plant

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    Rating: +7 (from 23 votes)
  7. Gweedo

    Have 2 400 w bulbs with hoods,bought them the same time,had 2 grows on them and I moved… When I plugged them in again about 2 months later one has blue tint and one has a gold tint…something I sould worry about or time for new bulbs….same everything equipment wise….thanx for your help….

    Did you get this sussed out?? Maybe got your ballasts flip-flopped?? I am curious as to what the solution was or what the cause was, in the first place.

    Best! -Gweieeidowe

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  8. geraldine goodnoh


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  9. WeedNeed

    Hi , i have lots of Blue LEDs , Red LEDs , soft white LEDs ( 2700 K ) and Daylight LEDs ( 6500 K ) , so i want to know does it harmful if I turn all these lights together for every stages of growing ? Or i must turn some on or off in different stages ? I know that in every stage some of them are unusefull but does it damages to plant if all lights are on ?

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  10. razz

    Q. room 5,5,5 what set up would u recomend for a newbie

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  11. Marc M.

    Have 2 400 w bulbs with hoods,bought them the same time,had 2 grows on them and I moved… When I plugged them in again about 2 months later one has blue tint and one has a gold tint…something I sould worry about or time for new bulbs….same everything equipment wise….thanx for your help….

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    Rating: +1 (from 35 votes)

    Something to cool off in handily might be a great
    addition to the garden plan. Leave them out for longer periods of time until the night-time
    temperatures are above 50 degrees. An informed purchase starts with reading product specifications and
    how they may relate to these very different types
    of gardening.

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  13. critical Jackie

    I’d like to know how the auto flowers do being pruned half way up the main stalk for max budding in the terminal bud? Does that even happen with autos like it would with a female or regular? And I’ve got a 125 watt blue spec CFL in my garden along with 2 x 150 watt hos. The mixed specs I feel will do gr8 but unsure can someone clarify please and thank you

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  14. ramtin

    I want to know how far MH and HPS lights should be from my plants?????

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  15. Old guy

    I use 2 600 watt HPS for 3×3 bed, 3 for 3×6 bed, I used to use MH for veg but now use new wider spectrum HPS for both phases, little difference. Without CO2 addition to room temp is 75-85 Farenheit, with elevated CO2 (900+ ppm) higher temps are beneficial and 85 to 95 is good. Without CO2 you want as much air circulation as possible, in a closed room plants will quickly deplete CO2 levels to 300 ppm. I never really got good results with lights less than 400 watts, and 2 is better than one. Enough light is really key to getting dense flowers.

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  16. Phil

    I’m already growing with a T5 setup. what can I do to improve the flowering? Do they make T5’s in the red spectrum?

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  17. Riverzone420

    Would someone please explain the possible pro’s or con’s with combining HID bulbs? For example, would introducing a small 150 watt HPS into a veg room running a 400 watt MH have a positive or negative effect on a plants vigorous growth phase?

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  18. alvin

    i use pc growing box,but i have problem with the cost of metal halide, i have 2 fluorescent 14 watt? i’ts enough? need answer please

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  19. Michael

    Just got a grow room 4x8x6 and would like some info on what equipment is best suited for this space also fertilizers ,soil mix ,etc

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  20. oldtimer

    Hi all newbee to site here I have a indoor room size is 3x6x6 im plaining on growing two plants having a hard time figuring out how many and what kind of cfls will I need to use to grow healthy plants grate site and thanks in advance.

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  21. tony t

    have been growing with led lights for over 3yrs. using lights by fuse led. a 300 watt and 90s.making some unbelievable medicine with them.friends using hid lighting want my medicine.growing bubba kush and og kush.Fuse led makes a great product and great customer service.use with grow tents you will be happy.

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    Rating: +7 (from 17 votes)
  22. terry208

    what do you think of using the 300w CFL grow light the one that is the size of a 2lt coke bottle? I use them with great success I only grow 1 plant (white widow) at a time in a 4sq. ft. mylar lined grow tent with a aluminum reflector and organic soil I never harvest less then 7 1/2 ounces per plant of almost unsmokable weed everyone thinks it’s laced and not even the most hard core smoker can take more than 5 hits

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  23. niko

    Dear friends,
    Hello from Europe.

    I want to know what about the GREENPOWER LED from Philips. Do we have any reviews? Can we replace the HID’S?
    What your recommendations are for use these kind of led lighters in medium size indoor canopy i.e. 4×5 meters?
    Thank you in advance.

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  24. Green Man

    You can follow either method. Naturally if you use two different bulbs, one for veg and one for flower at the different end of the light spectrum, you’ll yield more. But some people use CFLs the who’ll way through and have fantastic results.

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  25. larry

    when using autoflower seeds do you use a grow bulb first then flowering bulb, or flowering bulb all the way through in a 3 ft grow box

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  26. tony tantalo

    when growing with led lights a grow tent is highly recommended. use a 300watt light and you will be surprized with the results. the buds will not be as large as using hid lights but will be decent and the potency will be excellent.

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  27. John Doe

    I left a question on Sept 22,2013, But still have not gotten an answer. I am woundering if I am doing something wrong here…….?

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  28. Green Man

    CFL’s are more energy efficient however HIDs will usually generate bigger yields. CFL’s aqre a good option for smaller grows, or stelath grows as they don’t pump out as much heat as HIDs. If space isn’t an issue and you have a good setup where you can control the temps HIDs are the best bet.

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  29. Green Man

    General rule of thumb if you’re using HID lamps would be between 60-100 watts per marijuana plant. Naturally the more lights generally the bigger yield however it will affect other conditions such as temp in the grow room which will need to be regulated. CFLs are less efficient than HIDs and so you’d require more to get the same wattage.

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  30. RyMcGuy

    do different lights effect the quality of the plant? seems like the economic route would be using CFL’s. But if i were to use CFL’s the best way possible compared to using HID’s the best way possible, would the the HID’s have a better effect on the plants?

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  31. Jay

    How many watts per plant in both vegetative and flowering stages?

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  32. john doe

    Since lumens are the measurements of the TOTAL amount of VISIBLE LIGHT……..then when you are in veggie stage…….are you wanting to keep your kelins at 6500 and try to find the most amount (?) of lumens from a bulb….?…..

    Example : if a person has three plants in veg. , 3×3 space, would a cfl that rates at 200watts / 6500K / but only has 2800L… will this be not enough to grow with ???

    Sorry, but one more question……(thanks)…….say if you are using same area space above mentioned, if you were to use (two) of the same bulbs mentioned above, would the total of lumens be brought up to 5600 but the kelvin amount would stay the same at 6500…….?… this right ???? If this is correct, is this why people go with higher wattage bulbs to get more lumens ? ………thank you so much and you guys have a kick a_ _ site here….love it ..been a lot of help, you have no idea… guys break it down simple and easy for people like me. Thats right, I’m calling myself simple, that’s why I need to grow weed (lol)

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  33. Green Man

    We can only speak from our own personal experience and we haven’t had first hand ujse of magnetic induction lights. Thanks for the heads up though, we’re always looking to improve the site.

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  34. Daniel

    I’m surprised to see that magnetic induction lights aren’t discussed. The Inda-Gro 400 watt is by far a superior light to all of the above as it covers the full veg to bloom spectrum. I’ve been using these for years now and wouldn’t use anything else.

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  35. Green Man

    That’s correct, a blue light spectrum for seedlings and vegetative growth.

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  36. Heath

    What color spectrum do you use on germ/seedling process? Blue right?

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  37. Green Man

    First things first, are you growing marijuana or normal plants? Also do you know what strain they are? The best place for you to start would be our beginners guide which outlines the everything you need to know about how to grow marijuana.

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  38. stingray

    i am really new, i have tree seedlings on the window, growing for the wife, who is on a lot of meds, so any help, the have been in small yogurt pots for about 3 weeks, and have some leaves.. I am really new to this and on a carers allowence, so all help welcome.

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  39. Green Man

    If you’re working on a tight budget then i’d recommend CFL’s. They’re cheap to buy and run and are powerful enough to fully grow mature plants so will work perfectly for seedling growth.

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  40. Andrew

    I’m working on a tight budget and I only need bulbs for the germinating/ seedling growth process. What bulb would work best for about 6 seedlings?

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  41. cjay


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  42. Daniel

    I am just starting I have hade my lic to grow for about 10 years and I am now just getting around to useing it so I am looking for any and all the advise and help I can get I am starting in doors and I just germadate my first batch yesterday so hope fully I can get this going

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  43. Mike

    a dream come true. Just what I was looking for. Short ,sweet, and everything I need to know to get started.
    Like in cooking the simplest recipes get the most complements.

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  44. Keith Murray

    great advise all the info i need , ill let you know how we go.

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