The Cannabis Grower’s Guide To LED Grow Lights: Spectrum & Wavelength

LED Grow Light Spectrum

With the increasing popularity LED grow lights, manufacturers and distributors are innovating new ways to capture your attention.  They like to lace genuine science with a healthy dose of marketing hype in hopes that you pause just long enough for them to dazzle you with the latest hyperbole.  There are so many terms being thrown around, it can be difficult to dissect reality from marketing hype.

One of the common ways they try to get your attention is by talking about the light wavelength and spectrum used by their LED grow lights.  Here is a simple run-down of what is important and what isn't to help your LED grow be all it can be.

LED Grow Light Spectrum

When discussing light, spectrum simply refers to a range of wavelengths of visible light in the entire electromagnetic spectrum. Aside from visible light, the electromagnetic spectrum includes energy (radiation) from radio & microwaves, infrared, ultraviolet, x-rays, and gamma rays. Incidentally, the plural for spectrum is spectra not the often-seen spectrums.

In any case, grow lights are concerned primarily with the visible spectrum though, occasionally, utilize both infrared and ultra violet spectra as well.

LED Grow Light Wavelength

LED Grow Lights Wavelength
In terms of an LED grow light (or any lights for that matter), the term wavelength refers to the distance between peaks and troughs in a wave. Light wavelengths behave similarly to waves in water and their peaks can be close together or far apart. It is this trait that determines the color you see from red (long wavelength) to blue (short wavelength). Each shade of light along the visible spectrum can be measured in nanometers (nm) that range from 380nm to about 780nm, from blue/violet to red, respectively.

It is from within the visible light spectrum that plants derive all of the energy needed to conduct photosynthesis and grow. Taking advantage of how plants react to certain wavelengths of light is the basis behind the the development of LED grow lights.

How LED Grow Lights Promote Plant Growth

Even though HID lights have leanings toward a particular end of the light spectrum (blues for metal halide, yellow/red for high pressure sodium), they emit light in the full visible spectrum just the same way an everyday light bulb does. In general, plants respond in some fashion to all light, however, they get the most benefit from various blue and red wavelengths. Consequently, they get the least benefit from greens and yellows as most of it is reflected back.

Initially, LED manufacturers thought all that was needed was a single band of blue and a single band of red light - given at the right stage of growth - and you would have success. While this may have worked in limited testing on simple plants such as grass, it failed (or produced undesirable results) in more complex plants such as tomatoes and, of course, cannabis. This did not stop many manufacturers from blasting out poorly designed models in the early days of LED grow lights which is why this industry is still trying to separate itself from this bad reputation.

Necessary Bands & Wavelengths For LED Grow Lights

how to grow weed
Early adopters of this technology saw plenty of promise and, fortunate for us, kept pushing the technology further. What they found was that initial models were at least partly right - they had the concept of red/blue light down but it lacked in delivery. It was discovered that more wavelengths were needed in order to address the short comings of the first models. When looking at a PAR chart, you can see that there are distinct peaks along the visible light spectrum at which plants derive nearly all of their energy required for photosynthesis. It is clear that red and blue are needed and, until I did more research, I thought that orange was needed as well. The fact is that just 2 wavelengths in the red band and 2 wavelengths in the blue band can provide over 95% of the light needed for all phases of plant growth. Some manufacturers also deliver UV and/or infrared light bands in their products to enhance resin production and flowering.

Photosynthetic Pigments & Absorption Spectrum

There are 6 main photosynthetic pigments in higher plants that drive plant growth, flowering, and fruiting. Different pigments in the plant absorb light at various points of the visible light spectrum - both red and blue - for vegetative and flowering growth.

For example, lets take the most common/abundant photosynthetic pigments in a plant, chlorophyll A and B. The absorption spectra for chlorophyll A is both at 400-450nm (violet to blue) and at 650-700nm (near-red to deep red) while chlorophyll B peaks at 450-500nm and 600-650nm. So, while red is essential to flowering, it is also necessary for vegging. It also happens to be absorbed less efficiently by plants, hence the increased need for red lighting during flowering

Check out:
http://en.wikipedia.org/wiki/Photosynthetic_pigment
http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/Spectrpy/UV-Vis/spectrum.htm

My previous understanding of the need for orange in LED grow lights was based on what I know now as flawed science from this Solar Oasis patent . . .
http://www.freepatentsonline.com/6921182.html

Their research and testing were flawed which is where they came up with the 612nm (orange) and its importance to photosynthesis. While the reading is well within the absorption range for chlorophyll B, it is not at the peak of absorption. In their testing, they attributed growth to the 612nm while in fact, it was because of the 660nm they were also using (red). They also said that the orange excites carotenoids . . . which is just wrong as it peaks at around 439nm and 483nm as you can see here:

http://omlc.ogi.edu/spectra/PhotochemCAD/html/beta-carotene.html

What's Next For LED Grow Lights & Cannabis?

What we have now are LED grow lights that are optimized for full-cycle plant growth; from vegetative growth to flowering. Keeping things simple, light from the blue end of the spectrum is necessary for vegetative growth - making for strong, healthy plants with thick foliage. In contrast, red light is necessary for flowering and fruiting - producing large, dense buds along all of the nodes that were created, in part, by the blue lights. Remember though, it is not advisable to use single color LED grow lights (i.e. all blue for veg, all red for flowering) because you need a balance for the entire growth cycle.

While some companies are touting their full-spectrum and marketing 11+ band LED grow lights, others are opting to refine the current technology. It seems to me that the whole point behind LED grow lights is the efficiency and the fact that they are tuned-in to the precise wavelengths that are needed for photosynthesis. After all, we already understand that full-spectrum light produced by HID bulbs is inefficient, then why are some companies promoting their "white light" or "full spectrum" LEDs? In addition, adding on excessive bands of LEDs also results in a less efficient light - seems to be a step backwards, not an innovation.

I don't know exactly what the future brings for LED grow lights but I do know that there is one company doing the job better than anyone else out there. The exciting part is that the industry will continue to benefit from true innovation and research for years to come.

{ 49 comments… read them below or add one }

David November 30, 2010 at 3:15 pm

Great article and looking forward to hearing more.
Ive been an led grow light enthusiast and grower now for over 2 years and have found that when growing medicinal marijuana with a “great” led grow light (Im a legal patient) the end results regarding yield and potency have been exceptional. Most people who switch from floro or MH/HPS to leds have one very large thing to keep in mind…..leds are a completely different light than what their plants are used to. Fact: sugar/chlorophyll production is higher when using led grow lights than with conventional grow lighting. Taste any lettuce or basil grown under led grow lighting and the flavor is much greater. With no uneccesary spectrums to stress the plant out…..the plant can focus on growing and fruiting/flowering. Also……read this slowwwwly. Gram/watt ratio with leds is greater greater than HPS and cannot be argued. I have produced 240 grams of medicinal marijuana with 56 watts of led grow lighting……you do the math.
One thing many “home” growers look at is yield. Yield Yield Yield. They run a 1000 watt HPS and the needed air conditoning units to regulate temps…and they find after 2/4 months of flowering…their utility bills are sky high. For myself…someone who grows for personal use….this is money I shouldnt need to spend to grow my own. I dont sell any so I eat the costs….I dont think so…….at least not with led grow lighting. I can say with complete honesty after trialing an led/MH-HPS comparison grow…..Ill take leds any day. My yield was slightly lower with leds but my costs were 1/4 of what the MH HPS produced. So…to compromise 8o grams but keep $300 in my pocket and still have 1 and 3/4 lbs…..to me is worth every penny.
What most growers dont know…..is that the flowers produced from quality led grow lights are tastier, denser and have a higher THC content than with conventional grow lighting. Ive grown 30 different strains and the common problem with people who switch over to leds…is that they put too much regard into the “flowering times” they are told about. Do not use that as a guage when growing with leds. Flowering times will vary depending on the strain…but….will produce if given the TIME!!! Trust me. Im not here selling anything or promoting any companies…….Im a medicinal grower that wants to share his successes with led grow lighting. Hope this helps!!

Ryan Rodway December 9, 2010 at 5:56 am

Hi i was just reading your page as i`m looking at buying a grow light but i`m a bit unsure on the LED grow lights and i was hoping to get some advise on what sort of wattage i would need for the ammount of plants that i will be growing! i was planning on growing a maxium of four plants at a time so what sort of wattage would be suitable! Thanks

HydroMan December 9, 2010 at 12:28 pm

Hi Ryan –

I have seen micro grows using a single 90W LED grow light and a few plants put out great yields from a small space and I have seen trees grown each with their own 180W LED – it just depends on what kind of grow you are looking for and what your footprint/height will be. Let me know and I can guide you a bit more.

Thanks,
Hydroman

wazza January 18, 2011 at 7:33 am

hi.i am thinking about buying 3x 200w led panels approx 3ft x8in size for my setup to replace my 2x600w hps.these lights have 200x1w superlens leds per unit.can you advise a color combination/ratio and should i get the widest angle lens possible? these lights arent cheap so i want to get it right.thanks,Wazza

HydroMan January 18, 2011 at 10:12 am

Hi Wazza –

The only company I know that offers the best color combination/ratio is this one. If you have a minute, check out this 2011 LED grow light review. About 2/3 down the page you will see a section on micro-grows and commercial grows with a video showing a commercial grow from last year using LEDs. It is pretty exciting to see the results . . .

Beam angle can be complex as it depends on several factors such as height above the canopy, power of each individual LED, and the color of the LED itself. I would NOT recommend getting the widest beam angle available. In general, the wider the beam angle, the larger the growing area coverage – however, it comes at a price – reduced penetration power. The smallest angle I would recommend is 60 degrees . . . the largest is 120 . . . and I think 90 degrees is the sweet spot. At 60 degrees, there is slight increased penetration power however, it significantly reduces growing area coverage and has the potential to focus power too much on a single cola. A 120 degree beam angle creates a wide growing area but plant height would have to be sacrificed as the light tends to get dispersed a bit too much. At 90 degrees you get a great combination of penetration and coverage. This assumes that the LED grow lights you are interested in are using all 1W LEDs in the array – the numbers can change drastically when using LEDs with higher or lower watt values. Check out this article on 1w vs 3w LEDs and higher.

Let me know if you need more help,
Hydroman

BluntMan87 February 8, 2011 at 3:11 pm

I’m Heavily considering using some of the 357 LED grow lights in my up and coming medical operation, I’ve been doing a lot of research and I haven’t been able to come across a lot of information about the product, other than what is solicited by the site. In short I’m just hoping you can lead me to some actual testing data, possibly a few grow journals, things of that nature, to possibly help some of my doubts I may have for the products said capabilities.

HydroMan February 9, 2011 at 11:59 am

BluntMan87 –

The 357 Magnum is relatively new, however, the parent company has been around for 4+ years with a good deal of success – LEDgrowlightsdirect.com. I will see if I can dig up some grow journals for you and I will post them here.

I can tell you that I have seen a grow with these lights that was mind blowing – one 357 Magnum for each 6ft+ tall plant. Amazing.

Hydroman

Meh March 19, 2011 at 12:15 pm

I was thinking of buying a LED light can someone throw out good brands and company names so i can have a better idea of what to get when it comes to leds.

HydroMan March 22, 2011 at 1:22 pm

Meh –

Keeping it simple:

Prosource
357 Magnum
HydrogrowLED

Thanks!
Hydroman

PAPA June 27, 2011 at 4:37 pm

with led lights,do i use only red and yellow lights to flower or do i also need blue?

HydroMan June 28, 2011 at 9:48 am

Papa –

You will always need various wavelengths of red and blue throughout a plant’s life cycle . . . it just happens that red is what really drives flowering while blue drives a majority of vegetative growth – both not to the exclusion of the other.

Hydroman

John July 9, 2011 at 7:58 pm

I am fairly new to the growing. I have researched some and I’m considering LED lights, but the cost is still unclear. What is the cost to supply 3-5 plants with light?

Also, I’d like to contribute to Papa’s question above. If we know red is needed at the flowering stage and blue at vegetative, shouldn’t we use more of one than the other during their respective stages?

HydroMan July 10, 2011 at 1:49 pm

John –

To get an accurate assessment of how many lights you need, you would need to give more info about your grow such as overall height, grow space dimensions, etc.

A well balanced light is really what is needed from seed to flower. Once you have a well balanced light, you can supplement with extra red to get a boost on flowering or blue for veg but you would really have to make sure all other environmental factors were really dialed-in to get any benefit out of it.

Hydroman

ben July 12, 2011 at 7:12 pm

hi i was wondering if someone could help me. i hve a 4′x4′x6′ grow tent and and plan on trying to do a sog grow and i want to try led’s. i have only grown outdoors so not sure on what size or kind of lights to use. any help would be appreciated, thanks for your time

HydroMan July 14, 2011 at 5:01 pm

Ben –

How many plants are you planning to squeeze into that space and how tall will the finished height be?

Hydroman

ben July 14, 2011 at 5:34 pm

2 plants total and prob. set the screen 2ft above plants

ben July 16, 2011 at 7:33 pm

its a scrog grow not a sog my bad

HydroMan July 18, 2011 at 3:35 pm

Ben –

With SOG/SCROG you don’t have to worry too much about uber penetration power as much as you do actual coverage area. If you are planning on maxing out your entire 4×4 area with plants then you need to make sure every inch is saturated with light.

To do this, I like using multiple smaller light sources over a single large light. As is true with any grow light, if you are able to overlap coverage areas, your yield will benefit. In addition, with LEDs, interlacing the wavelengths from multiple light sources has a beneficial effect on the plants.

You can probably stick to a light with 1W diodes instead of opting for more expensive 3W. Not saying that you wouldn’t see a benefit from more power but since all your bud sites will be right on top, you don’t need to worry about hitting sites below a bunch of fan leaves.

I would recommend using a single light . . .90-180W . . . for each 2×2 space for flowering. During veg, you can get away with using just one or two lights . . .

Good options . . .

90W Illuminator
126W Penetrator (not the pro)
357 Magnum (coupon code MAGDEAL100 for $100 off each)

Thanks!
Hydroman

Shane July 31, 2011 at 7:21 am

Hi,
Thanks for the effort you’ve put into the site, much appreciated. I’m a bit confused about the third spectrum. You recommend orange yet the Penetrator, and I think the Magnum, use green. I would have thought that green is the last color you would willingly add to a grow light, am I missing something (perhaps the way the spectrum’s combine)?

HydroMan August 2, 2011 at 9:23 am

Shane –

Trouble with working in a constantly changing industry is that my content gets outdated quicker than I can replace or edit it. Based on current research and my understanding of things, orange in a grow light is pretty much useless as it does not target the absorption maximum for ANY photosynthetic pigment. Old research and even a US patent on a light pointed to orange at around 612-615nm as a key level to excite carotenoids, however, the absorption spectrum for carotenoids shows three peaks in the 400-500nm range . . . well within the blue spectrum, not orange.

Traditional thinking says that you want to avoid green as it is mostly reflected by plants anyways . . . which is why we have green leaves. However I have read research papers that show that green light is absorbed more efficiently than blue or red by photosynthetic pigments that are deep within a leaf (not surface chlorophyll). We are talking about a very small percentage but it is important nonetheless!

Thanks!
Hydroman

James August 18, 2011 at 6:49 am

Hey, Matthew!

You’re doing a great job helping explain things to us newbies!
I’m wondering. Do I need a 220 for my little grow closet? I’m
planning on using a cheap LED for vegetative, and one of the new
3W LEDs for flowering.
Would the cost in electricity be that much? I feel competent to
wire the room for a 120, but I don’t want to mess with a 220. Also,
I live in a small town (really small), and it would raise some issues
to have an electrician put a 220 in my closet!!
Thanks, man,
James

HydroMan August 18, 2011 at 10:53 am

Hey James!

Dieter August 28, 2011 at 6:47 pm

Hi hydroman. first i have to say your site is awesome sir.

secondly, I’m a bit confused.. With the regular lights it was clear that for vegetative state you need that color light and for flowering the other color of light. So my question is: do i need 2 differents kinds of LED lights with different colors for vegetative and flowering, or can i use one ( for example, 126w penetrator) for both flowering and vegetative and get decent results? and do i need a stronger light for flowering then for vegetative?

Thanks in advance!

HydroMan September 1, 2011 at 5:12 pm

Dieter –

Any lights in these reviews are great from seed to flowering. Two different lights not needed.

Cheers!
Hydroman

kottonmouthking October 12, 2011 at 9:09 pm

ok hi, i have a growing spot that i use for 1 plant and a time so im goin to try to explain how big it is so bare with me k =], when i look at the from it is 3feet7in in width wise, from the side it is 2ft5in’s and the hight is about 3feet, so what wattage of light will i need for that and can i get just 1 panel of leds or wil i need a couple for like the sides and the top?

thank u i really want to do the led growing and i only do 1 plant at a time so im thinking leds will help in results in yield since right now im using 2 65w plant lights (blue tint only) from the hard ware store that were 10$ a piece…..i think id like an led set up instead….

thanks again!

HydroMan October 18, 2011 at 9:38 am

KottonMouthKing –

With that sized space, you can do quite well with either a 126X Penetrator or a 180W Illuminator. You should see a BIG difference is the fullness of your plant and overall budding sites as well as larger, more dense buds as compared to using blue-heavy CFLs.

Cheers!
Hydroman

Alan October 18, 2011 at 9:03 pm

Hi, great site here, really helpful

I have a 4ftx4ftx6ft tent to grow in hoping to fit nine plants in, going to be using 12, maybe 15 litre pots, firstly will i need a bigger space to realistically pursue nine plants in that size of pot and secondly, what light (led) would i use? I was thinking 300watts but not really sure, whats the average price as well?

Lastly would i be able to compliment the plant throughout growing with cfl lights placed around it or is that a bad idea?

Thanks again.

HydroMan October 21, 2011 at 3:56 pm

Alan –

A 4×4 space can easily grow 9 plants to a solid 3 ft height. What you want to keep in mind with LED is not just the wattage going to the plants but the coverage in the space. What I mean is that a single fixture will not have the same coverage of multiple smaller fixtures even if you end up with the same overall wattage. In your case, I would recommend going with 40-50W per sq ft – similar to this commercial cannabis grow. This amount of power will get you professional results . . . equate to using 4x 180W, each covering a 2×2 square. Alternatively, you can go with a hobby style grow using 4 x90W, still offering good results, but more in line with a private grow instead of professional/commercial.

There would be no problem placing CFLs around the grow area – depending on how many and how you configure them, it could end up giving you a decent yield boost!

Thanks,
Hydroman

Phil October 28, 2011 at 1:45 pm

Hey Hydroman,

Thank you very much for creating this website.
I read most of it trying to figure the LED that better suits my needs, but i’m still confused… so i’m asking you directly.

I’m a beginner in growing cannabis, but i intend to get better so i don’t mind spending a little more money in a model that will suit future crops.
The space available is about 3′x3′ and 5.5′ tall, which is okay for 4-6 plants?
Since i’m starting i won’t go for any elaborate growing methods right now, so the plants might grow tall a bit (i don’t know the strain yet but i prefer sativa).

i selected a few models from Hydro Grow, Prosource and Magnum:
- 205W Penetrator PRO (does the Penetrator 189X give a better light output?);
- 357 Magnum LED;
- Illuminator 180W UFO;

- is this adequate to the number of plants i’m looking for?
- are all of them suited for european voltage?
- what would you recommend if i were to choose 2 smaller products that would cover this area but could also be able to adapt to other space configurations?
- i know you usually don’t point out to any specific brand but could you make an exception for this disoriented reader?

I’m sorry for the overload of questions.
Thank you once again,
Phil

Darek October 28, 2011 at 2:04 pm

Hello Hydroman. Can you write me what light do I need for 2×4 ft grow tent? I thought about two 90W illuminator. Is it enough good for pro results? I plan to buy LED’s from ProSource. Sorry for my lame english. :) Thank you in advance for help!

HydroMan October 28, 2011 at 4:13 pm

Darek –

With 2 x 90W Illuminators, you can get some really decent results – for professional results though, you would want 2 x 180W Illuminators for the same space.

Thanks!
Hydroman

Darek October 29, 2011 at 3:37 am

Thank you very much for so fast answer. I have a last question: I planning in the future to buy much bigger tent. So, I thought is maybe right decision to buy one 700W Illuminator SuperPro at once for the future growing space. But I’m not sure is that will be safe for my plants now, in the 2×4 tent? Is no risk to burn them? What do you think about it? Thank you for your help.

Moe October 29, 2011 at 5:56 pm

Hey Hydroman,

Thank you for helping in advance, awesome job your doing there.

I am trying to grow for the first time, I got these seeds from a friend and were trying to learn this step by step by reading honestly, now the problem is that we do not have access to any of the mentioned LEDs, how can I do this with normal Fluorescent light or smthing like that ? can you please list the things that I can use from a normal lighting supplier because here we do not have lighting for these purposes.

Thanks a lot
Moe

HydroMan November 4, 2011 at 3:19 pm

Hi Phil –

What you want to do is keep your space reigned in as a 3×3 ft max and you can still put in 4-6 plants in there. They would need to keep on the short side though given your 5’5″ height max . . . your plants will likely max out at 3ft or so to leave room for the lights and the buckets.

I would say that the best fit for your space is the 205w Penetrator Pro. The 189X needs much more vertical space above the plants to avoid saturation so would not work in your case. The Magnum and the Illuminator are both good lights but are not 100% suited to a 3×3 space.

What you would want to do is order the light and then either email or call up HGL to request the appropriate plug . . . though they are pretty good at figuring it out on their own anyway.

You may want to check out this grow guide too!

Later,
Hydroman

HydroMan November 4, 2011 at 3:22 pm

Darek –

Nah, I would stick with the 2x180W . . . the 700W would not burn the plants but would over saturate them with light and stunt their growth.

Hydroman

HydroMan November 4, 2011 at 3:26 pm

Thanks Moe!

You can have decent success with CFLs . . . check out

http://www.littlegreenhouse.com/accessory/lights.shtml

Just curious – what do you mean you don’t have access to LEDs?

Hydroman

T.W. December 5, 2011 at 10:10 am

Hey man, so can you use blue light exclisively during growth, then switch to red/orange light exclusively for flowering? Or do you need blue/red/orange to be present throughout all stages of growth/flowering?

HydroMan December 6, 2011 at 2:44 pm

TW –

I would never recommend using a single wavelength – though it is accurate to think that blue is used more during vegetative growth then in flowering. While blue drives vegetative growth, red also contributes to photosynthetic activity during this phase. Similar story with red and flowering stage.

So to answer your question – you need balanced light in all stages but you can put an emphasis on blue or red for vegetative and flowering stages respectively.

Orange is nearly useless for plants – I actually will be updating this post to reflect my new understanding of this . . .

Thanks,
Hydroman

Jim T December 19, 2011 at 10:52 am

Hydroman,

1.
I have a certain amount of respect for people involved in designing and testing LED Grow Lights as long they they are being truthful and not exaggerating, misleading,
or lying. In the near future, I’ll be selling Led Grow Lights, with the emphasis on giving
customers honest information on coverage. Rarely do retailers explain that in order to get square coverage out of a rectangular light(example: 20″x12″), you have to rotate your plants.
2.
In your post above,you suggested that Green LED”S were important , but in small percentages. As you know, Hydro Grow uses 15% Green in their “Gen EX” Series.
Does that sound right to you, or do you think that is a bit excessive? I’d appreciate it very much if you could email me at the address above.

Thank you very much,

Jim T.

HydroMan December 21, 2011 at 10:38 am

Hi Jim –

Your first point on rectangular lights is right on . . . either you have to move your light or the plant as there is no other way a rectangular light (which is directional by nature) will cover a symmetrical grow space.

As for green in LEDs . . . I have read a scientific report on the use of green for photosynthesis and it seems that it is mostly beneficial when also accompanied by moderate to strong white light as well. The idea is that it is acting on antennae pigments – photosynthetic compounds that, in this case, derive their energy from green/white in order to transform into a primary pigment such as chlorophyll A or B which operate in the red/blue wavelengths.

So the HGL lights may be on to something by using green but it would seem that any benefit from the green is lost due to the fact that there is no white light present. Also, the ratio of 15% seems high to me as well . . .

Cheers!
Hydroman

MaryJ January 10, 2012 at 10:43 pm

Hello all, Im new to growing and i am wanting to use a 180 w L.E.D light. So my question to you is. How big can my grow space be as well as how may plants can i successfully grow. Oh and one more thing all my seeds are feminized and autoflowering so no light change. yay.
thanks all ,
MaryJ

HydroMan January 13, 2012 at 10:37 am

MaryJ –

The 180W Jumbo Illuminator from ProSource (if that is the one to which you refer) can cover a 3×3 for flowering – so the number of plants just depends on your growing style. Could grow 2, could grow 25 . . .

Thanks!
Hydroman

Medicineman February 21, 2012 at 3:12 pm

Hey, first time grower here, I have a 4×4 room that I will be using to grow medically. I will be growing 4 plants with a deep water culture system using only LED full spectrum lighting. I have four 90w LED hanging lights and two T-5 for filler lights. I will be growing a short bushy medication and using nutrients the whole time. I have been told that all I have to do to switch over to flowering is change my light cycle, is this correct?

HydroMan March 13, 2012 at 4:18 pm

MedicineMan –

If you are using autoflowering seeds/strains, just keep the light cycle at 18/6. Otherwise, change your light cycle to 12/12 when ready to flower. You may also have to reduce the light height above the plants – depends on your lights!

Thanks!
Hydroman

Roy March 20, 2012 at 7:50 pm

Hi I was wondering is their a ratio for how many blue lights to reds? thanks

dickiebird April 16, 2012 at 6:36 am

Novice grower here. I have 2- 7′x7′x7′ room op. with the first one being a veg room with mh lighting, no real problems there, however in my flowering room I installed a 900w lighthouse blackstar led light. I have some issues here that are hard to quantify. Burned leaf tips to start off with, light airy buds and production another, taste seems good but the burned leaf tips are driving me crazy, I thought it might be over fertilization but on a controlled grow under hps lighting in my veg room there was no burn problem. The current belief is proximity doesn’t matter much with led lighting, but I think it must be. I’ve started a control grow with seedlings under the light at a distance 18″ and started getting burn problems within 2 days, ugh and moved the light farther away.
Is there any conventional wisdom regarding my issue as to distances from plants for leds? I’m sure there is some kind of radiation emitted here that can be counter productive. How effective would the light be if its placed at says 3-4 feet above the plants? Being a new product will it be all trial and error for me?

Hondo April 18, 2012 at 9:54 pm

I have a flower area of roughly 6×9 with a plant footprint of 4′x8′. I am currently using four 8 light T5′s for flower with mostly decent results. My main issue is power consumption, with fans lights blowers and HVAC all running the bill up much too high for stealthy production. After reading over the material on several sites I think I have a plan somewhat worked out. Based on area I am considering 6 of the 180W Jumbo Illuminator. The next question is with plants Vegged from seed for approximately 45 days and grown to about 12″ high, how many plants could I expect to flower to 36″ with this configuration?

HydroMan April 25, 2012 at 3:00 pm

Hondo –

6 will give good results for the 4×8 .. . go with 8 though if you have it in your budget. I would keep the grow to 8 plants – decently tall/bushy, each in a 10 gallon pot.

Later,
Hydroman

HydroMan April 25, 2012 at 3:07 pm

Dickiebird –

I would keep that light at 24-36 to start off with – wait till you see some growth then go from there. Keep in mind that nutrient requirements when growing with LED are a bit different as well as temperature and humidity. You can usually get away with less nutrients with LED vs HPS . . .. still could be a nutrient issue you have. Go with a 1/3 strength mixture and feed with every watering – just be sure to let the soil mostly dry out between waterings.

Hydroman

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