How to Fix your LED Spectrum for Flowering Plants

A quick picture of me with some of my plants… just one of my growth chambers.

Welcome!  My name is Dan, and I’m excited you’re here.

I study the science of photobiology and let me tell you, not many grow lights out there are giving your plants the colors they need… or want…

I can’t wait to share with you secrets about how plants are affected by color, how most grow lights on the market give out the wrong color, and what you can do about it without replacing your entire grow light system!

Today, we will fix the spectrum in your garden.  This means happier plants and bigger yields await…

Today is a good day to be you!

Use these tips to unlock better growth in your garden with a few simple steps — all under $100 and one is even free!  You’ve taken a solid step forward to fix your LED system’s spectrum.  Your plants will reward you!

By correcting the spectrum, you allow the plants to grow bigger and better.  Traditional LED lights starve your plants of required colors and wavelengths they expect in nature.

Sometimes the colors that common LED grow lights give out are all out of whack and your plants just “deal with it” … but aren’t growing to their full potential.

Just because your plants are staying alive and getting bigger… doesn’t mean they are thriving!  You may have bought these lights online, and of course they work, but have you experienced growth greatness?  Growing alone is hard enough as it is…why should we have to worry about light when all we are doing is trying to save power with LED?

The good news is, most of these fixes require only a small investment, and one is even free!

 After you read this, join in the conversation below and ask questions if you have any.  Feel free to post what grow light you have if you’re looking for specific advice.

I’m excited for you and your garden! Are you ready?  Let’s go.


All LED Owners – Temperature & Airflow Check!


Even though your LEDs might run nice and cool… you do need to keep those temperatures up in your grow tent to get maximum yields.

The High Pressure Sodium bulbs give out a spike of heat that plants actually love, so you’ll actually need to run your grow environment hotter than what you normally would with high pressure sodium.

This is good because letting your room get hotter means you need to use less energy cooling it!

Aim for eighty degrees, but 78-82 degrees is the sweet spot.

Because LED’s run nice and cool, it’s also important to get extra airflow over your plants, they breathe less without exposure to high heat – so be sure you have at least one clip fan blowing over the tops of your plants.


Attn: All Purple LED Light Owners With “Veg” And “Flower” Switches or Color Dials


Does your LED grow light have a “Veg” or “Flower” switch?  If so, stop turning off the  “Flower” or “Bloom” switch for veg …. unless you’re hoping to preserve a small plant in a nursery setting.

Depriving your plants of red light and dumping them with blue light will stunt their growth.  Just check out what happens to lettuce below in a scientific study when blue light % increased…

The reaction of lettuce when exposed to certain percentages of blue and green light.


They found that blue light actually stunted growth by reducing leaf size while also diminishing the rate of photosynthesis.  Crazy right?

What’s more, blue light is the color that causes the greatest stress and light burn.

If possible, run your LED light with both “Veg” and “Flower” turned on.  Back off the light to reduce the intensity, and your plants will thank you in return with vigorous growth!

If you have dimmable dials on your LEDs, during veg try keeping blue lower than what you normally would and observe the results…   Every photobiology study out there recommends Blue light to be lower than 30% for optimal results during vegetative growth for flowering plants.  If you could get that down to 15% it would be even better.

If you have Red/Blue/White switches, try your results with just “Red” and “White” turned on.  “White” actually has a lot of blue light, just enough to give what plants need so that they don’t “stretch”.

Interesting, huh?

Take a peek at your spectrum (more on that below) and use the information above to try to reduce the amount of blue, especially in your vegetative growth cycle because it will change how your plant grows and how big and fast the leaves expand.

Bigger leaves…faster growth…more harvest…

You will be blown away at the results.

During early flowering, when the leaf growth is slowing, turn on all of the channels at max power and let er’ rip.

Trust me…. I know it sounds like one of those statements on the back of a Microwavable Popcorn bag that says “Do not use your Microwave’s ‘Popcorn’ button” … but seriously… don’t use your grow light’s veg and bloom switches as they are intended.  You will end up with smaller yields.

Drop me a note below with a comment and click “Submit” with any questions and I will respond and help you “fix” your grow light’s settings! 


All Purple LED Light Owners


We’re trying to do two things with grow lights that have mostly red and blue in their spectrum…

  1. Blue Light Correction – This is the most important step to fix if your grow light has primarily blue light.  If you own a “ViparSpectra” this is definitely a step to take for you (this light is really meant for aquariums).  Try to find the manufacturer’s web page.  You’re looking for a spectrum graph.   You can also count the number of red and blue LEDs to get an idea. If there is an equal or higher amount of BLUE than RED, you’re going to want to fix that for all stages of growth.  We want blue light to be UNDER 30% and OVER 10% of the total spectrum.
  2. Full Spectrum Correction – Our goal here is to nourish plants with some full spectrum light (green/yellow) to help them thrive with more light information.  In addition, that should help your eyes out!  Adding white light will assist you in caring for your plants so you can see them in natural color.  A win-win!


My recommendation is to add a 50W Warm White LED Flood Light to your garden.  It’s about $35 with CREE LEDs, so you cannot go wrong.  Above all, it will snap most blue-heavy or red/blue spectrums into balance.  These flood lights are great to have around and I use them myself!  They are fantastic to use on their own for young seedlings and can easily be positioned into tight areas of your grow space.

Plus, the more light sources you have in your grow space, the better light penetration and spread you will have.  This means a bigger usable grow area and more growth deeper in your canopy.  What’s more, you can experiment with positioning these lights to the side and getting more angles of light sent towards your plant that will create bushier growth… Talk about an upgrade!

To start, find out how much your grow light pulls from the wall, not the advertised wattage.  For example, the Viparspectra 300W, while advertised at 300W actually pulls 136 Watts from the wall.  Be sure to find the right number.  You’ll have to search for it!

You’ll want to take Total Watts / 2 and shoot for that in your supplemental lighting.  So if Total Watts is 136, half that is about 70W.   We want about 70W of supplementary light.

If you have a ViparSpectra 300W, we’d want 1 or 2 50W Warm White LED Flood Lights for our light supplementation project.

What are you waiting for?  At such a low price to get started with just one, you can’t go wrong.



White And Purple LED Light Owners (The Best Solution)


Buy a low wattage HPS Light!  You will not regret it.  I work with production-level growers and if they are growing with LED, many of them are also supplementing with HPS bulbs.

The reason?  It works.

I know it seems counter-intuitive, but you will save MORE energy by getting GREATER YIELDS with the kind of yellow, red, and infra-red light that the HPS puts out.  Simply providing just a little bit of the colors that are missing in white or purple LED systems will unleash a huge amount of growth in your garden.

The quality and quantity of your harvest will increase for just a small investment…  It will snap your purple and white LEDs and turn them into a monster grow setup.

You will want to supplement your grow ideally with a 1:1 ratio of LED to HPS power.  Half HPS power is great as well.

For $70 and only 150 Watts of power, how can you go wrong?





What about Next-Gen LED Technology?

I never thought you’d ask!  If you’re waiting for the next big thing, you’ve come to the right place.

Now that you’re here and learning, check out our HPS vs LED Grow Lights: The Ultimate Efficiency Showdown article to learn even more!

Keep growing green my friends, and don’t forget to leave a comment below!


20 thoughts on “How to Fix your LED Spectrum for Flowering Plants

  1. Tony Cifuentes Reply

    Thanks for the information really good stuff just getting started with a cheap greenhouse so I have GPS light and led spectrum lighting have good seeds and will be trying on 3 small plants. Thanks

    • greensunshine Post authorReply

      Hey Tony, glad you enjoyed the article! Best of luck growing, stay green and keep at it 🙂

  2. Doc GreenThumbs Reply

    Really good read, thank you for the info.
    One question… I just purchased a 1500 watt COB LED set up. I got a great price for it and is full spectrum LED. The light is more Pink looking,/red. It’s only got a on/off switch and seems to be a great light.
    How do I know if it’s any good or not?
    It’s a BestVA 1500 COB LED, can you check it out and please get back to me?
    Thanks for the excellent read,

    • greensunshine Post authorReply

      Hey Doc GreenThumbs,

      I would say the BestVA is “OK”. The wattage on it is actually 300W, I am not sure where they are getting “1500 watt” from.

      The “COB” diodes that they are using are an older, lesser efficient style, but will “do just fine” however there is some better out there. I would say this “300W” light would be on par with a flagship “150W” “200W” LED light. Generally speaking, the cheaper LEDs found on Amazon are 50-75% as efficient vs higher end LEDs.

      All this to say you got a great deal on it, if you’re keeping it, I would definitely consider adding white LED floodlights to the mix (linked in the article) since that will 1) reduce amount of blue ratio and 2) fill in the white and orange spectrums for better growth.

      If you’re in the market for higher quality LEDs please stay tuned because we have an announcement for that coming up…

      Let me know if you have any other questions, happy to help!


  3. Greg Reply

    Hi Dan and thank you so much. I have a Mars Pro ll Epistar 120 LED in a 24x48x70 tent. I am very new to all this and need any help I can get. Please let me know about this light in this set-up and if I should supplement or do anything else you mentioned or even did not mention. If needed, I do plan on buying a better light (yours) when I get the funds. Again I thank you and look forward to your reply!!

    • greensunshine Post authorReply

      Hey Greg! Just checked into that one for you. Luckily the spectrum is pretty balanced already between red and blue:

      Mars Pro II Spectrum

      I definitely recommend keeping both switches on for the entirety of your grow cycle.

      Lots of airflow and higher temps will be key for you to get the most yields as stated in the article.

      The light does lack some infrared light and green/yellow light, so you’ll want to “train” your plants to be a flat table by topping or scrog-ing because the light may not completely penetrate the canopy, so you’ll want to keep that pretty shallow.

      Upgrades for you in the future would be to add some white light in there, but it isn’t critical, you should get some great results with your current grow light! Keep growing and when you’re ready to fill out that tent some more, add some more light sources to get more yield.

      Let me know if you have any other questions!


  4. Todd Reply

    Hey Dan, Two thumbs up for the article. My question to you is, I currently have a Spider Farmer 600w LED in a 3×3 tent. What is your recommendation on how to adjust my lighting?

    • greensunshine Post authorReply

      Hey Todd, Thanks!

      I looked up the Spider Farmer 600w and they have an interesting way of putting together the spectrums. The “Flower” spectrum is quite low in wattage, and the veg is very high, which is a different configuration I’ve seen most lights do.

      I would always leave “flower” on on full blast.

      When you’re in veg, what I would do is turn down the “veg” portion to about half and see how that works out for you to cut the blue down a little bit. Once you move into the later stages of veg and into flower, let er’ rip full 100%

      Let me know if you have any Q’s!


  5. Jaffa Reply

    That was very informative and genres of you to share this information thanks dan i am only new to grow and have made mistakes and still making them the biggest being farting around with the wrong lights if you are unsure about your lights do your self a favor if not your self do it for your plants scrape up the money and buy an es300

  6. Scott Reply

    I’m so happy that I came across this article. I have 4 Advanced LED 200 XTE lights and 2 Advanced LED 100 ‘s in a 5×5 tent. I’m growing scrog style and though I’ve observed Advanced Led’s recommended miniumum distance of 24″ , most times being 26-30″ away, I’ve always had light burn issues, leaves brown and shriveled, and the top of my buds were white. The garden is in first week of flower now and I’ll follow your advice to dial both grow and bloom up to 100%-well, I may back off on the blue just a tad now that I know that’s the spectrum that responsible for burning. As I progress into flower should I dial down the blue back to <30% and leave the bloom dial at 100%?
    Temp wise, I keep the grow room in the upper 70's as it is, these lights have IR & UV diodes so when working under them it can be uncomfortably warm, and I've actually had a sunburn after one extended session.

    • greensunshine Post authorReply

      Hi Scott,

      I’m glad you found value in the article. Blue and UV are the “strongest” wavelengths and can cause light burn. However, it is one of the lowest-needed colors for growth. It will harden leaves, make the leaves smaller, and make the plant shorter, which is good a good strategy for some species, but not for ones where we want the most yield and strongest “bush” type plants.

      I would experiment turning blue mostly off in veg and in flower if you think the plants can handle it, crank it up. Should have plenty of power in there even with the blues turned down a bit. I wouldn’t feel like you’re missing out on anything if you weren’t running full power on 1000W.

      Good luck!


  7. Bob Daniels Reply

    How would you use a viparspectra 900 and 2 viparspectra 600 for a veg and flower room?

    • greensunshine Post authorReply

      Hi Bob!

      Unsure of what room size you’re working with, however I would definitely turn on both switches in veg and back the lights off for bigger plants with less blue light.

      Good luck!


  8. wairo Reply

    great info
    i just start a 2 grow tent configuration ,
    1 4×4 with 600w HPS
    2 3×3 with 1500w COB blue light
    i wanted to veg on the 1500wCOB and move after to HPS 600w to flower , will this affect my plants ?
    also have more led lighs around to play with , 2000wled viparspectra and 1200w led,
    what can be a proper mix setup of lights ?

    • greensunshine Post authorReply

      Hi Wairo,

      Your plants will do fine with HPS in flower and 1500W COB in veg. I am not sure of spectrum, but you described it as blue. Would recommend placing some white in veg as well for less shock moving to HPS.

      For the extra LED lights, use them in flower with HPS for extra yield.


  9. Sillib Reply

    Hi Dan,

    Didnt realize this article was so fresh, glad to see youre still active in the comments section!

    I have a viparspectra 600, and as you stated in the article, it really lacks a red spectrum. I purchased a ‘HIGROW 36W All Deep Red 660nm LED Grow Light Bulb’ to enhance the red spectrum. I am in a 3×2 tent.

    I went ahead and purchased the LED flood light as well, and am just curious what spectrum I should expect from the flood light.


    • greensunshine Post authorReply

      Hi Sillib,

      Cheers! You picked up the right stuff for a nice budget correction. The flood light is basic but gets the job done for a good price. It will really help round out the spectrum in your grow tent. I would recommend hanging all the lights as high as you can and close together to get the best spectrum uniformity.

      To your healthy plants

  10. Sillib Reply

    Thank you for the reply! Glad I was able to make a correction in the right direction. Cant wait to see how these girls flower out!

    Last question; Would you recommend taking the plastic part off the flood light that is meant to protect it from dirt and water? Would it make the light more intense?


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