Hi guys.
Looking for some advice on lighting.
I have a grow tent 1.2m x 1.2m x 2m high and I’m running 2 x 130w cfl’s.
1 x2700k and 1x 25000k and for veg 1 x 6400k and 1x 14000k.
In your opinion is this too much light. I’m not having great success at this point, particularly in the veg stage. Thoughts ?

What type of problems do you seem to be having? It is really hard to get too much light with fluorescent lighting, T8s, T5s or CFLs. CFLs can actually put out a lot of heat. This could certainly be causing some problems if the heat isn’t under control.

Also, I’m not sure on what type of light spectra theory you are working with, but you might have some ideas about your light a little off.

Usually much above 6400K is not used at all. With Fluorescent lights usually one is only trying to get a little extra red or blue light, but in general the lights are mostly white and many can be used alone for the whole grow.

Much above 6500K and the light tends to look very greenish in a lot of fluorescent lights. And green is the light that is needed least by the photosynthetic process. This is why leaves look green, they are reflecting the green light that is not absorbed and used by the chlorophyll after the “white” light strikes their leaves (White light being generally made of equal parts red, blue and green light). Some specialty and high quality lights may be very good about keeping the excessive green light out and these lights may have good use if increasing the blue light is actually needed.

The lower you go in the K color rating number on light bulbs, the more “warm” or yellow/orange/red-ish the light will look, and the higher the number you go, the more blue-ish the light will look.

It is generally understood that plants use mainly the blue and red parts of light and that more blue light prevents unwanted excessive stretching between internodes. And that red light is more important for flowering/fruiting. And so blue-er lights are used for veg and redder lights are used for flowering. Also vegging takes place outdoors during the spring/summer when the sun is more directly over your area and fall/winter is when the earth is tilting away from the sun causing it to pass though more atmosphere (not unlike closer to sunset), and this is when cannabis flowers outdoors. One can easily see why these color changes might be used to replicate some changes in sunlight that occur through the different phases of growth.

So obviously the intent with most lighting is to replicate what the sun gives the plants in nature. And at least the colors produced by the sun that the plant can use. With LEDs, as the green is not needed, they can be made about a third more efficient than white light by not having to spend energy on producing green light, but in most other lights – as much “white” light is produced, there will always be some green light present.

In fluorescent lighting a rating of anywhere from 5000K to as high as 6500K could be called true daylight or balanced white light or pure white light, and all of these can be used for a complete grow, veg through flower alone to great success. Then the other colors are usually used to supplement the extra red or extra blue during the proper period of growth, veg or flower.

5500K to 6000K is the color of sunlight at high noon, approximately. 5000K to 6500K is the color of sunlight with various other conditions, including just before sunset and still bright(5000K) and overcast and kind of bright(6500K). Yes, the more exact color might change depending on altitude, possibly latitude as well as season, as this will change the amount of atmosphere the sun goes through and more atmosphere may further yellow or redden the hue of the sunlight, not unlike the way sunsets are more orange or red than the way the sun looks most pure white at high noon(5800K) when it is passing through the least amount of atmosphere.

I like to use lumens for simplicity, kind of like EC instead of ppm, as it is kind of the standard to which everything else can be converted to/from, or compared to, if you will. PAR is the exact photo synthetic active radiation(those mostly red and blue spectra), so you can usually kind of find out how many lumens of sunlight is equal to a certain amount of PAR, or the strength/amount of the red and blue that is equivalently found in sunlight(generally, more broadly some orange and yellow light is used in some of the plant’s biological activity). So most white-ish lights should have a lumen rating and this can help in determining how much light you have.

Keep in mind the farther away you get from a light source, the lumens will drop off significantly because the laws of physics, particularly the inverse square law. So most lights, when they give you a lumen rating, it is an approximation and it is at a certain distance from the light. This number can be greatly increased or reduced, geometrically so, by the closeness or distance of the light to the plant’s leaves.

And so, no matter the type of light, if you can find the exact specs for its lumens/FLUX per square foot (or the equivalent PAR) you can use this as a loose guide as to what you need as minimums:

Lumens(or equivalent PAR) per square foot:

Seedlings and clones require about 400-1000 lumens per square foot.

Vegetative growth requires about a minimum of 2,000 to 3,000 lumens per square foot.

Flowering requires about 5,000 to 10,000 lumens per square foot, ideally, and can take possibly much more.

10,000 lumens is supposed to be about the average power of the sun at sea level on a clear day at high noon, or something like that, lol. 8,000 - 12,000 lumens is supposed to be about the average power of the full sun without any overcast or no clouds depending on altitude and potentially other factors.

It’s not ideal, but you can make do with 2,000 lumens for an entire grow if necessary.

here is the light spectrum range of the cfl’s.
Using the 2700k and 25000k for flowering and the 6400k and 14000k for veg.
The reason I ask is the light too intense, particularly in the veg stage is, the little fellas seem to shrivel and die rather than bloom. Humidity is at 60% with good airflow. The soil is moist but not wet. Ph is neutral. I’m at a loss as to why they do this.

Well those charts don’t give us lumens or PAR intensities at range. And actually seem to have strange color concentrations. It seems almost as if the 6400K is the worst lights for photosynthetically active radiation.

Chlorophyll absorption peaks are 430 nm (blue) and 662 nm (red) for chlorophyll a, and 453 nm (blue) and 642 nm (red) for chlorophyll b. Chlorophyll b is not as abundant as chlorophyll a, and merely help in increasing the absorption range. A slight amount of the nanometer range that nears the yellow/orange can also be somewhat beneficial.

The main info I’m lacking is that might be a big factor is the temperature of the growing area and if possible the temp at the canopy and the temp of the ‘root zone’, the soil in most grows, and maybe the reservoir, soil-less media or rockwool cube in hydro. If these get too hot or stay too hot too long then you will have problems.

As humidity is good and pH is neutral these should be good. but what is the nutrient strength in the growing medium? The NPK values of the soil or the EC/PPM of the soil’s run off? Are you starting the seedlings in some nearly nutrient free starter soil? starting them with too strong of nutrients could be what causes them to shrivel up before they can really get going. Nutrients shouldn’t be added until the little seedling has a well developed root system, as indicated by a few sets of true leaves and alternating nodes.

Cheers MacGyver
The 2700 & 6400 are 8000 lumens and the other 2 are 10000 lumens.
The grow room is 21 deg Celsius.
The soil has no added nutrients but is rich in organic composting from years of gardening.
The nm range is shown on the chart and they seem to fall within the appropriate range.
The soil temp is quite cool but I cant be precise.

I guess I should point out. As I’ve been unable to receive the seeds I ordered from ILGM, I’m using seeds from a successful outdoor plant. But I’m unsure if this will make any difference. These have been started in cotton wool and clean soft water only.
I hope this info helps.
I will stop using the 6400k asap as it seems useless with the info you have provided.

Do they state the 8,000 or 10,000 lumens are at a specific distance from the bulb? This could be important in determining exact lumens at a specific distance and at what coverage. I’m going to guess maybe that rating of lumen intensity is at, say – 30 or maybe 60 cm from the bulb, maybe even up to a meter away from the bulb and then is maybe recommended to maybe cover a square meter. But I doubt one 150 watt cfl really has numbers that high at a meter away from the bulb. It might be only 10,000 lumens at a distance of 30 cm and only cover 30 square cm at that level of lumens. Like I said it is really hard to get too much light with fluorescents. And keep in mind, because of the inverse square law, at twice the distance, the power does not only drop by half, but much much more than that: Inverse Square Law for Light

But in general 600 watts to even up to maybe 1000 watts in as small as a square meter is usually not too much light as long as the heat is kept under control. These numbers are usually used for HID but they should loosely hold for fluorescent lights as well.

I really don’t think it’s the light.

Keep in mind, organic compost can have too high of nutrient content. Just because it’s natural and organic doesn’t mean it can’t burn your plants. Dog pee is natural but look at what a mess it makes of a nice green lawn.

This is the idea that keeps sticking out. I’m leaning heavily towards nutrient burn from too “nutrient hot” of soil. Actual temperature in your soil sounds like it shouldn’t be contributing to anything. Cool as 21 C or even a bit lower is just fine, we just don’t want it too high or freezing cold, this can damage the roots.

Cheers MacGyver.
Thanks for the info. Learnt a bit from that :slight_smile:
I’m confident the soil is not contributing to the problem.
It grew the outdoor one a treat.
Trial n error for awhile. I can’t expect the first indoor grow to be perfect. Just wish I could get the little darlings into there 4th and 5th sets.
Appreciate your help.

It is strange. What is your feeding schedule or are you relying on the nutrients in the soil only? Are they maybe starving?

I don’t think the outdoor seeds have anything to do with it either, after all technically all plants are outdoor plants. And I’m sure our seeds will get to you and if not there is our guarantee, just contact Claire or what have you if need be.

How long have they been vegging when this happens?

Have you seen the “support ticket”?

Maybe if you notice anything we haven’t already covered, point it out and answer it to the best of your ability and maybe it will give us some ideas:

ILGM Support Ticket:

What is the strain?

Indoor or Outdoor? If outdoor, planted in ground or in a container?

Size of space?

Soil or Hydro? Type of Medium used?

pH? Of the soil or medium (root zone) and of the water that is fed to the plant?

Type of nutrients used? NPK? EC/PPM levels?

Temperature? Day vs. night temp or highest and lowest temps? Root zone temps?

Humidity %?

Light system/watts/lumens/FLUX/PAR?

Number “weeks/days” from into Season, Vegetative Growth or Bloom/flowering?

I have used only one 1000 watt bulb from the begining now we are into the 10th day of flowering with 2 1000 watt bulbs. Even with 3 fans going it staya very warm. The tent is 76x76x76
My question is: would it hurt my ladiies if i switched over to 600 hps to help keep the temp down


It is hard to say what type of reduction in growth the plants will produce with less light, No getting around it, less light means less yeild.

This is true Stoner, i’ll have to come up with sometime to help keep the heat down.

Thank You Stone
Be cool