Grow Lights 101: Best Plant Growth Spectrum Color? White vs Red/Blue LED + What is PAR & ePAR Light?

Do plants use more light colors than we realized? What does the latest horticulture research mean for grow lights? What's the best color spectrum for growing plants?

This video is all about Light Quality. What effect do different light wavelengths have on plants and their development? Do plants need UV light? How does Far Red light effect plant growth? Do plants use green light or is green light wasted energy? These questions are answered, along with scientific research that you can read more about, depending on your level of interest.

00:00 - Intro
00:32 - Kelvin Color Temperatures
01:28 - Visible Light Spectrum
01:39 - What is PAR Light?
02:38 - Do Plants Use Green Light?
04:30 - Benefits of Green Light For Plants
05:07 - Photomorphogenesis
05:25 - Do Plants Use UV Light?
05:51 - Do Plants Use Far-Red Light?
06:25 - How Plants Use Photoreceptors
07:11 - What is ePAR Light?
07:46 - What is the Emerson Enhancement Effect?
08:33 - How Plants Use Green & Far-Red Photons
09:07 - Is Full Spectrum Light Good For Plants?
09:36 - Custom Light Spectrum vs Plant Shape
10:57 - Is White Light Good For Home Gardeners?
11:59 - How Do LEDs Make White Light?
12:44 - What's the Best Light Spectrum?

We'll take a look at the visible light spectrum (a portion of the electromagnetic spectrum). Why is it better to analyze grow light colors by their wavelengths rather than using generic Kelvin ratings? This video answers: What is PAR light (Photosynthetically Active Radiation)? It also looks at the McCree Curve & the Emerson Enhancement Effect. And we'll see how to define ePAR (Extended Photosynthetically Active Radiation). We'll compare the efficiency of LEDs, fluorescents, high-pressure sodiums and metal halides.

When considering LED vs HID, the spectral composition can be a major factor. Some LEDs have a few limited color bands, using only blue & red light. Some include a "full spectrum" light source. How do they make white light from LEDs? This video explains phosphor coated white LEDs. Are these white LEDs good for plant growth?

How do plants use green light? How does far-red light help plants to grow? What about plant photoreceptors?

This is the basics of plant lighting and grow lights. It is intended to benefit a broad audience, from home gardeners, to greenhouse growers, to vertical farmers and even "medical" growers.

#GreehouseGrowers #LEDLights #IndoorGardening #knowledge #ArtificialLighting #GrowLights #Albopepper

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[cFyugThCzvAqYaGmxRgfCKTuvHMEjQ]

As a new hydroponics chilli hobbyist with a background in electronics engineering including radio & optics, this is exactly the level of depth and clarity I like to see in informational resources. I will now stop worrying about possible inadequacies of my white LED setup which costs 3x less per watt than commercial grow lights

[a.rostamifard]

As an electrical engineer who is assigned to design such horticulture led grow lights, your video helped me so much. Can't thank you enough.👏

[dogmosatchmo]

Something nobody seems to address is using straight blue, red, or blurple lights, prevents you from seeing the plants true health. Leaf color is an important tool for determining the health of your plants, and I quickly learned if everything is glowing red or purple, you never see the actual leaf color, and deficiencies can go unnoticed.

[Zissou]

This is incredibly helpful, I had never considered anything beyond "growth, " but to break it down into specific response behaviors to various wavelengths is revelatory!

[matneu]

As an hydroponics beginner I ve learned so much about the relationship between plants and light in a great and not boring way 👍 I started with self built led lights for my well planted aquarium in times where no manufacturers had seddle on led and always used human eye friendly light and the plants grew well.

[yellowice]

Honestly one of the most informative and well researched videos on what lights to use for growth, I learned about the far-red and green being used for plant hight which might be beneficial (or detrimental) on how much space you have and how big you want the plant to grow

[NENEMIES]

I used a few of those giant spiral florescent bulbs to grow plants in a small space and they worked fairly well. I did switch to the red white and blue led light though for the next crop and did see much better results. The led lights also create less heat which is a great added benefit.

[TickiTucki]

Great video. I started using the grow LED lights for starting my children in winter and then throw them at the sun when it gets warmer but I quickly realized that white LEDs work just fine and are way better to work with. So that's my experience, simple, cheap white LEDs.

[bronwynreijnders]

I got a purple grow light on sale and my orchids are doing MUCH better.
I would like a normal sunlight lamp but weirdly enough THOSE are stupid expensive where I live.
But I can definitely say that adding a lamp has dramatically improved my plant growth over the windowsill

[raahauge]

This is exactly the video I was looking for. Thank you very much. Had to skim 4-5 home-grower videos where different lights were tested on a single plants. I wish these home-growers had seen your video before they started to experiment themself.

[marambula]

i’ve been binging these hort lighting articles the past few days and stumbled upon this video and your channel. You are excellent in your delivery summarizing the state of the research! Respect!

[ysrlxmt]

At last, I understand the science behind light spectrum with regards to plant growth

[ToneD]

I have been using burple led's for the past few years with tremendous results. I did find that the color of the leaves were unnatural, but with that in mind, I carefully monitored the nutrients and ph levels on a regular basis. My auto flowers produced remarkable THC levels and the amount of buds was very pleasing.
I did finally relize, every grow is different and we all learn something new every grow...!!!
Peace &Love to my fellow growers. M/F
✌👍🤘

[Andrew-untx]

I have used LEDs since blurple lights came out over a decade ago. I bought two Mars Hyrdo FC3000 lights last year and they are impressive. Low heat, no noise and they grow solid nuggets. I have had colas that weigh over an ounce using these lights.

[tazzyhyena]

I am very much a more casual gardener. This was a fascinating look into something that I would have never considered due to my more layman knowledge around this stuff

[Secret_Moon]

PhD in horticulture here. Very good and well-researched video, although there are a few things I could add.

Regarding the usefulness of greenlight, it would largely depend on your light intensity. The image at 4:17 explains it very well. Red and blue lights are very efficiently absorbed by the upper plant cell layer of the leaves (or, in whole plant term, the upper leaves), so they can't penetrate very far into the lower cell or leaf layers. While this seems an efficient harvesting of light energy, in high light intensity it's actually not. Since plant cells/leaves need CO2 to photosynthesize, concentrating too much absorbed light energy into a single cell/leaf layer will cause CO2 depletion in that layer, and all that absorbed light energy will not be fully utilized, and may even cause leaf burn from the excess energy. Green light can penetrate deeper into the leaf/canopy, therefore spreading that light energy out to more cells/leaves, reducing the concentration of light energy and local depletion of CO2. However, it is true that green light is absorbed less efficiently by leaves, with 20 - 30% reflected and wasted. When you have low light intensity that's not enough to cause severe local CO2 depletion (as in most cases of indoor growing with artificial light), red and blue lights are more efficient than green light. So, there's some truth to those purple growing light marketings. Of course, light color doesn't only affect photosynthesis, but plant morphology and other physiological aspects as well, and those effects may in turn affect photosynthesis (for example, blue light causes more compact plants, as you mentioned, which could cause more intra- and inter-canopy shading and reduce total light harvesting). But that's a whole other can of worms and would largely be on species-to-species basis.

About far-red light and photosynthesis, the Emerson's enhancement effect is not something that proves you need far-red light. It simply proves that chloroplasts have two separated photosystems (I and II, with PSI having peak absorption at 700 nm and PSII at 680 nm), and photosynthesis works best when both photosystems are active. On the whole leaf basis though, that is indistinguishable, since light bouncing around inside the leaf will blur any boundary between those 20 nm, even if you could find single-nanometer monochromatic light to illuminate the leaves. For far-red light, while it is true that light up to 780 nm can still drive the photosystems, the amount is very small, and most energy would be wasted as heat, which is not ideal for indoor growing system. Far-red light has far more secondhanded impact on photosynthesis by affecting plant morphology and physiology (such as elongation, leaf angle, stomatal conductance) through phytochrome. But you only need a little bit, and from my experience, putting more than 5 - 10% of far-red light into your light may have adverse effects on plants. Most white and red lamps, including LEDs, do have some spillover light into the far-red range. Also, as light filters through your leaves, part of it will be converted to far-red light. Combined, they're more than enough for your plants to grow normally. So don't go putting too much additional far-red light into your system, you'll just waste energy and heat up your chambers.

[schlowe]

I've always been skeptical of certain grow light types and stuff, simply because the original glow light in the sky will always be better than a commercially produced one intended for profit. I use them indoors during colder weather and to help with the occasional pest control with bringing everything inside during the winter, but first opportunities I get everything goes back outside.

[gabumonboys]

Perhaps the most useful video I have seen for understanding indoor grow lighting!

[camillosteuss]

Thank you very much! Its been years since i went to agronomy and agriculture college, and i do remember well the red and blue spectrum wavelengths as noted by the algae chlorophyll, but i too always considered green a relative waste due to deflection, yet i never considered it in perspective of large tissue like leaves, which are bunch of watery cells or partial mirrors, which while they do deflect and reflect green, they also do so in every direction almost, due to geometry of the cell and the fact that the green part that does reflect green light is inside the cell, not on surface, like skin, which would pretty much block, but instead, here, the green light can enter, deflect in all angles and actually serve a very good role in stimulating photosyn. in deeper layers, where red is famous for its short penetration in anything but vacuum, compare to more powerful blue, which doth travel further... Damn nice work man, a good approach and explanation... Also, this will actually do me some good in practice, or not me, but my plants during winter, as i will now not shirk the green light for my population of citrus and other non winter loving plants...

[seanhewitt]

I employ both a super high pressure sodium hid and a full spectrum (4000k) led lighting system for my indoor flowers, but I use the red, blue, uv and far red light bars with a 6400 k blue/white for my veg cycle.