How many lumens does a plant need each

Thread starter #1
i will be growing 3 feminized seeds from a new strain i ordered. Can anyone tell me if a 150w hps and how much cfl lumens i will need i have both 6000k and 2700k for each stage and have y adapters and a 4 way bulb adapters for the drop lights to have 4 bulbs or more on each plant with the hps above everything.
so i heard 6000 lumens can anyone help? thanks

Fuzzy Duck

Well-Known Member
Not that lumens has any thing to do with plant growth as its a measurement of light visable to the human eye only !

Its more about PAR, light spectrum & qualitie of it.

But anyway in a nutshell…

Lumens per square foot:

Minimum amount of lighting needed is around 2000 lumens per square foot.
(Two – 23 watt CFL’s, per square foot*)

Mid range is around 5000 lumens per square foot.
(Three - 23 watt CFL’s, per square foot*)

Optimal is 7000-7500, or higher, lumens per square foot.
(Five – 23 watt CFL’s, per square foot*)

*I’m only using CFLs as a reference here, with the assumption they’re kept at a distance of 3 – 5 inches from the plant. It is important to understand that the “penetration” (the farthest measure that quality light reaches down into the plant canopy) will at best be only a few inches deep.

Watts per square foot (wattage per sq ft WILL vary by light source):

Minimum wattage per sq ft.: 30w
Mid Range wattage per sq ft.: 50w
Optimal Range wattage per sq ft.: 50-80w
Thread starter #4

Fuzzy Duck

Well-Known Member
would 24,000 lumens of light be sufficient for 3 sq feet? 150w hps and strong 6000k and 6500k cfls that hang close to the plants is what i am using right now
Its more than enough.

I would be inclined to switch the 6000k over to 2700k for the flowering phase tho :peace:
This chart is interesting:

It's a list of lumens-strenght at different heights from bulb, for 250, 400 or 600 HPS.

What I'm asking is: what does "optimal light" mean in this chart?
Fat buds?
A plant barely surviving?
Popcorn buds?

I ask because "optimal light" seem to have a very big range:
At 21 inches, a 400W HPS gives only 5000 lm, and that is defined as "optimal light".
At 22 inches, it's "too little light".

This cannot be correct? I'm not sure how to interpret the chart, please help :)
i found charts giving the lumen output of both MH and HPS globes of various wattage, the closer to the plant the more lumens it recieves but you have to maintain decent distance to avoid burn but at like 5 inchs a 400w hps put out a 100,000 lumen so pending on size of ur plant the bottom canopy should recieve still like 25,000 lumens.. I have my light to move left/right/up/down so can get stronger light below too. Mayb GrowAddict means the same chart?? If you do a certain grow u can better dispense light over ur plant. Goodluk And Happy Harvesting;)
This chart is interesting:

It's a list of lumens-strenght at different heights from bulb, for 250, 400 or 600 HPS.

What I'm asking is: what does "optimal light" mean in this chart?
Fat buds?
A plant barely surviving?
Popcorn buds?

I ask because "optimal light" seem to have a very big range:
At 21 inches, a 400W HPS gives only 5000 lm, and that is defined as "optimal light".
At 22 inches, it's "too little light".

This cannot be correct? I'm not sure how to interpret the chart, please help :)

Take a look at that chart. Who decided that "optimal light" is 5000 lumen AND 63500 lm?
Obvioulsy, "optimal light" is not big buds..... I wish that chart was better.
Hi Grow.. Yeah thats the one i have mate.. It is saying that the 'optimal distance' is the preferred range that the light will put out certain amounts of lumens for your plant. So in between say 3 inches above ur plant and the 22 inches ur plant will get at the top of the canopy '183,000 lumens for a 400w, while the lower branches, below the 19 inches will recieve less than 4,000 lumens, its basically saying that your plant at lower levels recieves less strength light, tho still able to grow ur plant, just slower than the tops closer to the light.. So you want to keep your lights close enuf without causing damage and i use a 400w and grew a 5 ft vert and the base levels matured abit slower but still was ready..That chart i found handy.. Its prob not 100% accurate but give you an idea anyway..You dont wanna put ur 250w say 22 inches above ur plant!!Or she will struggle.. I kept my lite at 8 inchs above tops. Goodluk and Happy Harvesting;)
OK Grow here's most my stats for ya... I kept my light always more than 6 inches from tops of my plant, to avoid burn, or bleaching or any stress its got a fan blowing directly underneath the light to help dissapate the heat. My plant reached 5ft tall at harvest time, ALL TOPS ( except maybe three small bottom levels like 4 inches above soil that were under alot of shade) grew well and each weighed between 8-14 grams when dried.. Some lower tops still made excellent bud, they still pulled at least 5 gram dry cola's and branches were full of bud.. So to answer the last 2 questions, only the first maybe 3 or 4 small levels werent as big as the rest, tho still a nice smoke-great high, and the only ones that were id say popcorn bud branches were stuff all but again, only due to shading factors i had trouble with on last setup.. otherwise id have to say a near perfect grow..Hope this can help you abit, just try to make sure ur branches are getting sum light on em and not always shaded,tuck or tie sum fan leaves if have to, and ur girl will grow ok.. Goodluk and Happy Harvesting;)
Thanks for answering, but guess I should speak to the one who made the chart - as "OPTIMAL light" should give optimal sized buds - and it does NOT.

I want optimal light-levels, but not only for my cola at the top.

So I look at this chart, and it says "OPTIMAL LIGHT LEVEL" all the way from the very top down to only 4000 lumens... I call bullshit - that'll NOT give optimal sized buds.

So how far down the lumen-table make for medium and popcorn-buds only?
That is what I want to avoid, and I want to harvest it all at once - not top part of plant first to let bottom grow.

You can help me (please):
1. How many inches above the top of canopy is your 400W HPS?
2. How many inches tall is your plant, from the very top down to pot-level?

3. How many inches down your plant does your 400W HPS give you real good buds (at harvest)?

4. At what height does buds only yield popcorn, if at all?

Thanks, your experience with your 400W might help me a lot in my current situation.
I was born the year of the Rosenberg execution so i qualify to be here.

I want to start by stating that when most people think of pot users they think of teenagers or college students. I admit I had the same preconceived notion but if you want to see the face of marijuana users go to a dispensary. The majority of the ones i have seen are wellllll over 55. You will see the same blue haired people that hold up the line at Krogers on Senior Citizen Day looking for their coupons.

Growing a few plants is a great hobby for seniors and can even supplement our social security checks. Most seniors are going to be puttering around in the garden anyway growing tomatoes or roses. Not only do we get free (well, kinda free) medical marijuana but just growing and caring for our plants is very therapeutic. I enjoy listening to Iron Butterfly or Hendrix when caring for my plants. I even have a lava lamp.

I am on my 4th grow. My 1st grow i had just tossed a few seeds in flower pot with some old dirt in it on the back deck. By accident it was the right time of year and i actually grew 5 little plants about a foot tall that yielded almost an ounce of free weed! My next grow was at the bird bath with my zinnias and grew about 6 ounces of perfectly acceptable smoke. Growing outside has some negative aspects to it especially if you are growing in a state where it is not legal. I strongly discourage outdoor grows in that situation.

My 3rd grow was inside. i grew 9 plants using 400 watt cfl for veg and 1000hps for flower. I made just about every mistake possible and still harvested 17 ounces of mid grade weed. Maybe not medical grade but definitely as good as any mexican street weed.

I am now 2 weeks into flowering of an indoor grow and I'm ready to offer some advice.

1st off STRAIN MATTERS. I buy clones from my dispensary. It saves about a month of growing over seeds and being some strains take longer then others to grow it's good information to have. you will also be assured of getting female plants. male plants are baddddd and you don't want your girls anywhere near them or you will lose most of your usable yield and you can't even get any effect from them. IMPORTANT NOTE: learn about male plants and destroy them on sight. If you are growing for your own use (and maybe a little more) i suggest 4 to 6 plants to start. i'm of the mind that it's important to just grow the 1st plants to prove it can be done. You'll probably wind up getting all the different kinds of lights and hoods and nutriants and gauges at some point but for new growers you can get by with a couple of the large 300watt cfls from loews for the veg stage (get the big ones, not the 3 way ones, they wont work.) the longer you veg them the bigger the yield but do yourself a favor for the 1st grow and veg for 4 weeks. you will need some "nutes". there is a big debate about the evils of miracle grow but keep it simple this time (believe me, there are enough different nutes out there to make your brain explode). for the flowering and budding stage you are going to have to invest a little money in a 600 watt ballast, hood and bulb. check craigslist. there is a lot of grow equipment and broken dreams out there. you should get by with about 150 bucks or less. if you decide growing is the right thing for you you will want to step up to the 1000watt grow lights for future grows. Expect a 50 or 60 dollar hit to your power bill for 4 months or so. your plants are going to flower for about 9 weeks before they are ready to harvest. that gives you plenty of time to study for the next crop.

There is a very special feeling about growing your own stash. You will probably start to treat "your girls" as pets and you will want to nourish and care for them. Go ahead and crank up some Santana and give it a shot. Let us know how it turns out.:thumb:
Hi Uncle Butch,
Have you checked out the "over 50" threads? There are lots of us old farts on here! Good post and summary of your grows, and as a few members signatures state, growing is more addictive that the smoke. I was in the MJ game in the 70s too, but spent most of my adult life out of the scene. I wouldn't have thought the Nixon mentality concerning MJ would ever abate, but I am seeing it happen before I die and it is about time. Reefer Madness looks like a comedy skit now, but back then it was intended as truth and advice from Big Brother. I'm so glad people as declining to "drink the Koolaid" and see the reality for themselves. Like alcohol is less dangerous ... NOT! Imagine being able to have this interaction in 1970. Glad to see your post fellow old guy! Oh yeah, did you not get high from seeded weed back in the 70's? Why are the male plants treated like "cancer" to people now? Maybe let one grow go to bud without culling the dudes. I did just that in 2013, and it although it did yield less, it was the most awesome White Widow I have personally grown, both taste and effect were top shelf. Just my experience though, perhaps you have a different one to share about males in your grows that was negative?


Best of Buds


Now that I know how to grow a bit i am actually embarrassed about stuff i said about pot 40 years ago. i used to tell people that "i had a friend" that grew pot and whenever he wanted he would just pluck off a few leaves and smoke a joint. i thought the buds were an unwanted growth of the plant and i always insisted on buying the shake but to be 100% honest i enjoyed the high i got from the old smoke better then i like it now. Maybe it was because smoking was usually a communal thing and i was surrounded by friends and we would sit in a circle and pass the joint around, it usually took several joints to get everyone stoned but that just gave us time to laugh, listen to music and enjoy each others company. It is a little sad that the potency of today's smoke is so strong that it isn't necessary to work at getting high. There were always rumors about "2 toke dope" way back then but I didn't believe it really existed. Good times. Good times.

I think it is sinful that so many lives were, and are being, destroyed for political reasons. By far the most damaging thing about pot is the laws. It all starts to make sense when you realize the governments game is to divide us in groups so we all get the "We vs Them" mentality.It serves the governments purpose for all of us to hate each other.I see weed as one of Gods gifts and there is not a force on this planet that will convince me otherwise. To put it in the same category as crack and heroin is criminal in itself. I live in a state where i can grow and possess. When i tend my plants I think of all the people that are serving mandatory life sentences in federal prisons for doing the same thing. I am a staunch advocate of weed and often tell non-users that being i am a drug addict i want to go out and rob and do violent acts but i figure i'll have a sandwich and a maybe a nap 1st. But I am serious when i say that prisons should be flooded with weed. Give the prisoners all they want and make it so abundant there is no market for it. toss in a few guitars and a supply of munchies and let them do their time getting stoned and writing songs. Let them mellow out and they will be in a better frame of mind when released.

As far as male plants are concerned i had a very bad experience with my 2nd grow. When my plants sexed i had 1 male plant that was behind the the females. i got my lobbers out and cut it as low as i could reach. i disposed of it and didn't give it any further thought. when i harvested the females i was sickened to see that i had cut down the male right above the 1st node and there were 2 little string bean looking growth and all the pods had burst. the little runt had fertilized my 8 females cutting my yield in half. That is why i have an attitude towards male plants but you said something that really interest me.

I am a new grower and everything i have always been told is you can only get high on the female. I am not terribly impressed with todays smoke for a few reasons but i would be very interested in knowing more about budding a male plant. it may be the high i am looking for.


Well-Known Member
In reply to the OP: What you have to understand is that light intensity falls off with the square of the distance from the source (regardless of color temp or type of bulb). Meaning at two feet away from the light source you have 1/4 of the light as at one foot away! At 3 feet and you have 1/9 the light of one foot! Simple physics. This is not an issue outside with the sun, because the square of the distance of ~93 million miles plus 6 feet is only minutely different than the square of the distance of ~93 million miles plus 0 feet.

For this reason, I grow with plants bent over and growing up to and contacting 32W T8 6500K tubes. The T8 tubes are cool to the touch. The plants have nice green fat leaves on them (of course, I also feed them soluble fertilizer in their water; they are in pots in soil). They get good light from 'top to bottom' even with measly quad 32 watt tubes, because they are really close to the bulbs. The are running 24/7. Now, these are mother plants and I am vegging, and I am trimming off the side branches that are growing vertically and rooting them as clones. Another option is to run a series of T8 tubes vertically in a circle around your plants that are left vertical. They used to make MJ grow boxes like this a few decades ago (I do not know if they still do or not). That way all the leaves get the same amount of light, up to the length of the tubes.
I am currently running CFL lights to the times of 8700lumens per plant at the rate of 74w per sq ft. I keep them approx 1.5"above the plants and that's helping to keep them short.. But man they have leaves and branches going everywhere and not even 2 weeks old yet. Btw 6500k on all bulbs this far.. And these are s.a.d. Autoflower strain. Healthy happy and vigorous as heck. Temp 77f RH68% soil temp at the roots are 67-69F pH soil and water 6.6-6.8. i think the girls were listening to MacDonald commercial because they're loving it. Lol I am getting my new light this weekend T5 4' ..12 bulb 650w unit.


Grow Journal of the Month: July 2017
Re: How many lumens does a plant need each

Can email or.text pics and also have co2 bag in tent. Hell help help.
should use PAR instead of lumen to valuate a grow light.
Lumen use for valuation the brightness for human eyes.