Clamp-on CFL Grow Light 2700K/40W....

[Ray]

One foot candle is one lumen projected on one square foot of area.

Start with the "initial lumens" of a bulb - a reasonable rule-of-thumb is that T12 fluroescents put out about 40 lumens per watt, while T8, T5, and CFLs put out about 90.

That means that the 28W CFL will have about 28 x 90 = 2520 initial lumens. Keep in mind that it isd radiating in all directions from the spiral tube, with some of it lost to the inside of the coil. With a decent reflector, you can bound most of it toward the plants, but I'll wish you "good luck" trying to estimate what the intensity is at the leaves.

Concerning red or blue affecting what - the fact is the plants need both, and a 2700°K bulbs really doesn't provide much of either - it's just heavier in the red end.

Take a look at these articles to learn more:
Artifical Lighting
Artifical Lighting Intensity
Light Sources & Color Temperature

[Vanda lover]

I have been considering doing the same thing. It seems to me that any added light would have to help. Our windows face south, but they are small windows and are shaded quite a bit, and our climate has little sun in the winter. I'm using a spot grow bulb [a large one] but am finding it to be too hot and drying.

[johnblagg]

Originally Posted by Ray

Unfortunately, not very...

Secondly, a 2700K bulb has almost no light output in the blue end of the spectrum,which is critical for blooming.

HMMM not to dismiss your considerable knowledge Ray you are usualy 100% right on stuff ,but I think you got that one reversed ...I thought the red end of the spectrum was better for promoting blooms?

Maybe it is dependent on what kind of plant it is?I know the pot growers swear by Hps for promoting bloom because its higher in the red and say the blue is for vegataive growth....

[camille1585]

Originally Posted by johnblagg

HMMM not to dismiss your considerable knowledge Ray you are usualy 100% right on stuff ,but I think you got that one reversed ...I thought the red end of the spectrum was better for promoting blooms?

Maybe it is dependent on what kind of plant it is?I know the pot growers swear by Hps for promoting bloom because its higher in the red and say the blue is for vegataive growth....

Must be a typo on his part, I even double checked this, red= good for blooming and blue= good for growing

[Vanda lover]

I've been looking into the LED lights. There are some cheaper ones on Ebay, but it's hard to say how good they are. There are some very expensive ones that have fans in them that would be great--if they were reasonably priced. I think that they are too new yet, so the price is still high.

[NeoNJ]

Ok, thank you all so much. I'm getting there ....slowly. What I need to know is if I should just replace (throw out) the 2700k bulb and replace it with a 6500k bulb ....If so, can someone let me know what size wattage bulb I should buy and lumens?

How about a CFl 6500k 200w 75 lumen bulb ????

[johnblagg]

no do not throw it out ....I use 65 watt 2700k bulbs and my orchids do fine under them...and a higher wattage would be good but if they are actual 40 watt bulbs they in fact are as high wattage as normal t12 shop light bulbs .

use it untill you find something better and even then it will still help.I have 4 65 watt cfls 3 2700 k and one 6500k spaced over my grow area ...while I also has a 250 watt hps that one is cebterered over my phaius to bloom it.I also have a 100 watt metal halide on one side of another table and it is to supplement my den aggeratum with higher light levels...

Keep it and use both when you get another bulb....

[NeoNJ]

I have the fixture, and it is in place, with the 2700k bulb. My light meter indicates 4000-5000 fc of light.
The light meter is on the windowsill itself, and the 2700k bulb in the fixture is 3-ft. above the light meter, and the light meter is registering 4000-5000 fc. so I think I have plenty of light with this Clamp-on fixture for the orchids that I am growing in the size space they are growing in.
So I'm keeping the 2700k bulb, and don't feel a need to have a 6400k bulb along with it.

[Ray]

Maybe I stated that backward, but as I said later, plants need both parts of the spectrum.

Go to this web page and select or enter the 2700K:
Light Sources & Color Temperature
You'll note almost no light in the blue end of the spectrum, and in the red part, the energy density is about 0.8 x 10E12 J/m4.

Then enter 6500. The density in the blue end is about 130 x 10E12, and the red end is about 110 x 10E12 - 130x greater than the 2700K bulb.

If you grow exclusively under all red light, you will not get extra blooming, but will develop weak, leggy plants instead.

[johnblagg]

very true that light mostly into the red spectrum will cause leggy growth but I get pretty good result using 65 watt cfls of the 2700k type.....

2 bulbs over a 4 foot by 2 foot area at 18 inches above the plants ....my plants are not leggy and I have bloomed two this winter that were the only two of blooming size I had ....the rest are growing very well and should bloom I think in their season this year ....