Optimum Spectrum for Veg?

I've been reading up on the effects of spectrum on Marijuana plant growth. Much of what I'm researching pertains to Flower cycle only, like the Emerson Effect, End-of-Day, and UV for increased trichome production.

But I need to replace a couple veg lights so I am looking at strips for that, and thinking about doing 4000k CRI98.

Does UV have any real benefits for veg cycle? What about far-red or IR?

It has been said that adding in red as well as lower K that it promotes a longer internode lenght. Do you want that?
A more blue has been said to keep the plant short with shorter internodes.

Definitely don't water longer internode. Looking for bushy and shorter internodes. That's why I'm going with 4000k. But wondering if UV helps in veg any?

[QUOTE = "tilopa, post: 16021100, member: 202186"]
Определенно не поливайте более длинные междоузлия. Ищу густые и короткие междоузлия. Вот почему я собираюсь с 4000к. Но интересно, помогает ли УФ-излучение овощам?
[/ QUOTE]
делает их карликами

tilopa said:

I've been reading up on the effects of spectrum on Marijuana plant growth. Much of what I'm researching pertains to Flower cycle only, like the Emerson Effect, End-of-Day, and UV for increased trichome production.

But I need to replace a couple veg lights so I am looking at strips for that, and thinking about doing 4000k CRI98.

Does UV have any real benefits for veg cycle? What about far-red or IR?

Click to expand...

4k or 5k will work great for veg

brazzik25 said:

делает их карликами

Click to expand...

благодаря

4000k 98 cri would be great i bet.

sounds expensive though. 6400k flourescent has worked great for me.

I only use UVA/UVB for a couple hours the last few weeks of flower.

Cheers, GL!

Bottom line question, does it really matter in veg having CRI 98 vs regular CRI 80? Meaning will the plant grow better, i.e healthier and/or faster?

tilopa said:

I've been reading up on the effects of spectrum on Marijuana plant growth. Much of what I'm researching pertains to Flower cycle only, like the Emerson Effect, End-of-Day, and UV for increased trichome production.

But I need to replace a couple veg lights so I am looking at strips for that, and thinking about doing 4000k CRI98.

Does UV have any real benefits for veg cycle? What about far-red or IR?

Click to expand...

Blue side of the lights will keep the plant short... more red light will stretch the plant.

In the old days people woukd veg with mh... a more blue side and then switch to hps in week 3 of flower.

This kept the plants shorter in the stretch period... works really well if you want shorter plants for indoors

oill said:

Blue side of the lights will keep the plant short... more red light will stretch the plant.

In the old days people would veg with mh... a more blue side and then switch to hps in week 3 of flower.

This kept the plants shorter in the stretch period... works really well if you want shorter plants for indoors

Click to expand...

Yes, good points. But, I am talking about Color Rendering Index, and you might be talking about Color Temperature. And I just did some research on the difference between these and I'm still not sure about what it actually means. As I understand it the higher CRI gives a broader color spectrum, it will include higher percentage of color at 430nm, for example, that a lower CRI. But the intensity of that color is not necessarily higher.

So, if I want a higher concentration of blue (generally speaking) then I could use an led that is 6000k and CRI 80 and get plenty of blue to help the plants be more short and stout, right? But at CRI 80 that "blue" would only include a small intensity (like maybe 15%) at 430nm whereas with CRI98 would include perhaps 40% at 430nm, for the same K value.

So, to the point of my question, and I know there has not been a lot of research done on this so maybe nobody can really answer. But does the extra range of the spectrum that a higher CRI gives really make much of a difference in veg. The reason I want to know this is because if not I definitely don't want to spend the extra for CRI98, but if it helps with more vigorous growth without I lot of vertical stretchy growth, then I'm happy to spend the extra.

tilopa said:

Yes, good points. But, I am talking about Color Rendering Index, and you might be talking about Color Temperature. And I just did some research on the difference between these and I'm still not sure about what it actually means. As I understand it the higher CRI gives a broader color spectrum, it will include higher percentage of color at 430nm, for example, that a lower CRI. But the intensity of that color is not necessarily higher.

So, if I want a higher concentration of blue (generally speaking) then I could use an led that is 6000k and CRI 80 and get plenty of blue to help the plants be more short and stout, right? But at CRI 80 that "blue" would only include a small intensity (like maybe 15%) at 430nm whereas with CRI98 would include perhaps 40% at 430nm, for the same K value.

So, to the point of my question, and I know there has not been a lot of research done on this so maybe nobody can really answer. But does the extra range of the spectrum that a higher CRI gives really make much of a difference in veg. The reason I want to know this is because if not I definitely don't want to spend the extra for CRI98, but if it helps with more vigorous growth without I lot of vertical stretchy growth, then I'm happy to spend the extra.

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Anything above 80 is good to grow. But also I don't think it matters... I would assume blurple lights have a really low cri rating and they can grow ok buds.

I think you are overthinking imo. 3.5k for flower and 5k for veg..... the cri on a 4.5 k is normally higher than say a 3k light because the sun is closer to 4.5k.

CRI can be pretty relative.

we should more look what we want to have in our spectra and go by their charts.
cri 90 and above is often offering a wider spectra in our case and more punch in the 660nm region.
if you dont want to spend the extra money on cri98, maybe check out the 5700k 90cri EB3.
they go quite low with their blue and shouldnt pronounce any unwanted stretch.
the cri 80 version of the 5700k doesnt look bad to me too, similar range, while the cri 90 offers a more even spectrum and is better in the red region.
(page9).

"optimum" is subjective, but most LEDs and kelvins/cri can get the veg job done imo...... Flower cycle is the "money maker" in the end= minimal stretch, low yield. That's when you break out all the bells and whistles (uv, high cri, fr, top shelf diodes,etc) for a better end product.

If you got some t12/t8 fluoro fixture laying around?, led 4000/5000k retrofit bulbs are readily available at big box stores/Amazon. Led high bay fixtures too for dedicated veg area.

cobshopgrow said:

CRI can be pretty relative.
we should more look what we want to have in our spectra and go by their charts.

Click to expand...

Sounds good. My question is what do we want to have in our spectra? So, the 5700 has strong blue, but the red is really weak, like 40% in the 600nm range. Is that too little red? Could that cause some problems in slow growth?

Anyway, the question is probably moot because I cannot find gen3 5700 CRI 90 or 80 for sale anywhere.

tilopa said:

Sounds good. My question is what do we want to have in our spectra? So, the 5700 has strong blue, but the red is really weak, like 40% in the 600nm range. Is that too little red? Could that cause some problems in slow growth?

Anyway, the question is probably moot because I cannot find gen3 5700 CRI 90 or 80 for sale anywhere.

Click to expand...

FWIW i would not go over 4000k with LED. The spectrums are way different.

4000k 80 cri is fine for full spectrum. Adding some 630nm and 660nm and 730 nm will bring that cri up to 90+ if you want but that would be more for flowering. For veg the 4000k 80cri is fine.

But as i said earlier 6400k flouro is much better

pulpoinspace said:

FWIW i would not go over 4000k with LED. The spectrums are way different.

4000k 80 cri is fine for full spectrum. Adding some 630nm and 660nm and 730 nm will bring that cri up to 90+ if you want but that would be more for flowering. For veg the 4000k 80cri is fine.

But as i said earlier 6400k flouro is much better

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This doesn't make sense to me. You are showing a graph for 5000k fluorescent that is high in the green and red spectrum and week in blue, when all I've been hearing from others is that for veg high blue is better.

the graph makes sense.
white line is the sun as reference.
every color temp from 3500k to 6500k should do the trick for you.
i do use 6500k led for veg and it gives nice healthy plants with good roots, seedlings do like it a lot too.
think the biggest problem people have changing from cfl to led is that the intensity of the leds is way higher.
the higher color temps have the benefit of a wider and lower going blue, therefore i would give them a try.
one major difference between cfl and led is that cfl emits a little uva, so maybe worth trying to emulate that as good one can with lower blue namometers, its just a guess.
if you can get some 4000k they will do the job great too.
i do also like these 4000k 95cri buddies for veg btw.

cobshopgrow said:

the graph makes sense.
white line is the sun as reference.
every color temp from 3500k to 6500k should do the trick for you.
i do use 6500k led for veg and it gives nice healthy plants with good roots, seedlings do like it a lot too.
think the biggest problem people have changing from cfl to led is that the intensity of the leds is way higher.
the higher color temps have the benefit of a wider and lower going blue, therefore i would give them a try.
one major difference between cfl and led is that cfl emits a little uva, so maybe worth trying to emulate that as good one can with lower blue namometers, its just a guess.
if you can get some 4000k they will do the job great too.
i do also like these 4000k 95cri buddies for veg btw.

Click to expand...

I understand what the graph is representing, I just meant I do not like the spectrum of florescent for veg and would never choose it over LED.

I've decided on these: EB Gen3 Thrive CRI 98 5000k.



I'm going to do 8 1120mm for a 4x4 area at the nominal current of .960A @ 40.6v for 311w. Using a HLG-320-42 all parallel. The price is about the same as the Gen3 CRI 90s I bought last year, which I was surprised at, I thought they would be more. But they are a much lower efficiency.

311 watts my be over kill for a 4x4 veg?

tilopa said:

I understand what the graph is representing, I just meant I do not like the spectrum of florescent for veg and would never choose it over LED.

I've decided on these: EB Gen3 Thrive CRI 98 5000k.

View attachment 4784262

I'm going to do 8 1120mm for a 4x4 area at the nominal current of .960A @ 40.6v for 311w. Using a HLG-320-42 all parallel. The price is about the same as the Gen3 CRI 90s I bought last year, which I was surprised at, I thought they would be more. But they are a much lower efficiency.

311 watts my be over kill for a 4x4 veg?

Click to expand...

do a side by side. I thought the spikey spectrum was weird and made no sense. I built a 5k led veg light. Spent over a year with red stems, 3 and 1 prong leaves, overfed, underfed, deficiencies etc. switched to a cheap 6400k fluorescent and all my problems went away. I’m not saying 5k led can’t grow plants just that it’s not as easy to do as with flouros. If you do go led id go 4k and like 15w/sqft with plenty of vertical headroom.

graphs don’t grow plants.

think you hardly can go wrong with 5000k cri98 for veg., very nice blue region would say.

i think that the emitted ppfd makes the difference between cfl and led, less the color temp/spectrum.
i had red stem problems pretty much every time i overdo it with what they can take, its not so easy to dial in in veg, took me some time.

nothing spectacular, but i left one clone under 6500k and put the rest under 3000k 80cri few days ago.
the ppfd are comparable, just the color temp differs.
while its not so easy measure, the 6500k is about 200ppfd at the tops falling of to the sides to 100.
the 3000k is pretty much everywhere 160ppfd., stressing the plant more.
they seem to be a bit healthier under 6500k always.

6500K, was the weakest of 5, leftover.


3000K since a few days, more red stems.


oh and iwould say 310w of your strips is too much in veg, for a 4x4 , but as long you can dim, find it out and tell us.