1 foot-candle = 1 lumen per square foot.

The lumens (or foot-candle) rating of electric bulbs is a measure of how much light will land on a surface that is 1 foot away from the light source.
So in your 20,000 lumen set, you would be getting 20,000 lumens 1 foot away from the source, and the intensity deteriorates quickly as you move away from the source. You will not be getting 20,000 lumens for an indefinite distance.

You can use this to your advantage, by placing the high light orchids closer to the light source. The low light orchids will need to be placed farther away from the light source.

Hi Ramesh,

1 fc does pretty much equal 1 lumen, but that is the amount of light you get at the actual source, not a foot away. At a foot away, light levels have pretty much dropped by half. All that light is also spread out more or less evenly over the entire area covered, although the middle is brighter and the ends are a bit darker. Also, what is written on the packaging does not mean that's what you'll get. Your best bet is to borrow, beg or purchase a light meter and measure the actual output where the leaves of your plants will actually be. And, yes, the closer you are to the light source, the brighter it will be. Light levels drop off very quickly the further away you get.

Anyways, I do grow Phals and Ascocentrums, along with a couple of Dendrobiums. My Phals are under a shop light fixture, with two 4 foot 40W fluorescent tubes. Ditto for my Ascocentrums, but they are a lot closer since they are smaller and need more light. I also supplement this light with compact fluorescent bulbs (abbr. CFL, they're known as the energy saving bulbs, since they use most of the energy they draw for light rather than heat, like the regular bulbs). I use the 42W bulbs, which are said to be equivalent to 150W. The Dendrobiums are under four 4 foot 40W tubes and are also supplemented with CFLs. The problem there is that Dendrobiums can get tall and unwieldy.

Now, one of the secrets to success with lights is remembering that while your orchid and its relatives may get say 1,500 fc per hour in nature, what really matters is the total fc received per day. So say that in nature, your Phal gets 1,500 fc per hour and that the day lasts 10 hours. This means that your Phal needs 15,000 fc per day. Unfortunately, with the lights you have, you can only give it 1,000 fc per hour. What to do? Extend the length of the day to 15 hours. 1,000 fc X 15 hours = 15,000 fc per day as much as the first scenario. (This is of course an overly simplistic explanation, but you get the picture.)

Good growing.

Julie

My experience is that you will not be able to grow anything but low light level plants under standard four foot fluorescents. 3300 lumen tubes only produce about 1000 footcandles at the bulb and as noted earlier go down significantly below that. Yes, at a foot away you are clear down to 500 or less. To grow medium light orchids you will need expensive high output fluorescents or HID type lights. mike

That's pretty much false.

I used to bloom a Vanda under 4' fl. tubes but, here's the key, it was also in front of a window. However all but the most high light requiring plants can be bloomed with just regular flour. light. It's all about how long you leave them on. A 'snapshot' of the light may indicate that it is too low, but when the same intensity is maintained for 14 or 16 hours, the plant will get enough. Go by the leaves. If they are dark green, its not enough light. Light green on its way to yellow, is enough or approaching too much. A more valid worry, IMO, is that usually all the light comes from above which can cause some odd growth at the sides of plants.

Without a greenhouse or sunroom, I've found that putting the plants in front of a window with shoplights above and spot lights for the sides, works quite well.
-MB

Which statement is false? That one can only grow low light orchids under four foot tubes? I happen to agree and don't think it is a false statement at all. 3300 lumen (40W) tubes are pretty much a thing of the past, even with four 3300 lumen tubes you were lucky to get 1000fc at 6". With the T8 33W tubes the average lumen rating is in the 2800's. I doubt one can do better than 500fc at 12" as was stated. Thing is, for flowering plants of any kind life pretty much begins at 1000fc and only goes up from that.

The people that manufacture lights and or the consumer reporting agencies that exist to annoy said manufacturers both use light meters that are far more costly and accurate than anything that you or I can purchase through Charley's Greenhouse Supply. Why not let them do the work and when you need to know how much light your four tube light hood is putting out consult published website data?

Light from windows has similarly been quantified by researchers with access to much better measuring equipment than is practical for the hobbyist there is no need to second guess them. It isn't only a matter of economy their data is also likely to be more accurate!.

Finally, even with my considerable experience I could not tell you (especially with a new plant) by the color of its foliage whether or not it has enough light. There is too much variability with different nutrition or root moisture issues that also have an effect on foliage pigmentation. By far the best measure of light level IMO is observing the ongoing process of growth and development of the plant structures. Many accept stalled plants that have no discernible development for months on end as 'normal'. It is not. Growth and development of an orchid in good light is clearly observable. I haven't found that I need to change my 'benchmark' of 1" of foliage growth at the leaf tip of phalaenopsis and intergeneric hybrid orchids. Cattleya and Dends can be assessed in much the same way even though they are somewhat slower in overall development.

H

As from reading Howards post for some time now, adding light is always a great idea. As I have money avalible I always go and buy another shop light and plunk as high of a cfl bulb I can find in it. I have about 30 orchids ranging from phal and paph light level to dend and vanda light needs. after I installed the fith lamp was when the growing started. The phals and such were growing some but everything else was very slow. Now I have new growth on everything and even got my noble dend to flower for the first time. Everything has new growths and a catt has set a sheith. So as this summer continues I will add yet another light as none of them are showing any light damage and I will continue adding until they do show they are getting too much light.

So I guess all this remabling just means what you have will probably keep them alive, but add more light every chance you get.

Really the only thing I was claiming is false is:
"To grow medium light orchids you will need expensive high output fluorescents or HID type lights."

Maybe it all depends on one's definition of 'expensive' eh? I guess it also depends on one's definition of 'medium light'.

I firmly believe that, aside from those various types that grow in full or nearly full sun, the rest get such a range of light intensities throughout a day from clouds and overhead tree branches or cliff faces or a lemur sleeping on the branch, that the constant intensity over 14 hours with regular 4' tubes and CFLs can make up for the lack of lumen output.

I definitely think it's a good idea to err on the side of more light if one isn't getting growth or blooms that one is happy with.
-MB

I've been growing under fluorescent tubes, CFL, HID and whatever else I can find for the last 5-6 years. On my 3-tiered 4/40watt tubes per tier light cart I regularly flower mini-catts, dends, some Onc's, neo's, masdie's, and of course paphs & phals. Each tier is set to a different height and I try to keep the top of the plants within 2"-6" of the lights. The only plants I have had problems with are the larger catts and the large vanda type plants. I run my lights anywhere from 16 to 13 hours a day (shorter during the hot months, longer during the cold months). My cart, 3 shelves 4'x 2' taking up only 8 sq ft of floor space, is really a benefit to me and I just would not think of ditching it for something else. I may consider switching it over from T12 to the T8 lights/ballast one day, but in any event I will keep and use the cart and it's current footprint.

I also have 2 tanks with the 4 pin CFL's and 6/85watts CFL's covering a 2' x 8' grow area of mainly larger plants. I used to grow under a 400 watt MH and a 250 HPS light set-up (way too much heat with this set-up, replaced 3 months ago with the 85 watt CFLs) so I do understand about higher light and it's benefits.

I agree with Howard and Clint that more light is better, but with the right positioning and the right # of hours, my experience says that most things can bloom under standard fluorescent lighting.

Throwing even more light at the 'kids may be beneficial, but in my situation I'm happy with the overall cost/flower ratio that I'm receiving. More light = more cost (more electricity to run the lights year round and more electricity to cool the house/grow room for 6 months of the year.)

Speaking of cost I actually figured the cost one of running my 5 CFLs and even though I live in rural NY I used Cali rates for electricity just to err on the sind of high cost I came out to being something like $30 a year to run then 14 hrs. a day. I agree more lights more cost, but these cfls are great on the expence side. besides mo' money mo' problems right?

Switching from HID to CFL's was a two-sided savings for me.

Not only was I able to lower the total watts ([6x85]=510 vs. [400MH+250HPS]=650, equals less electricity consumed) and increase the total lumens ([6x@5250]=31500 vs. [@20,000+@10,000]= 30,000), but I am also generating much less heat (less electricity to cool the room & house), good in summer, not as beneficial in winter.
The other advantage of the 6 CFL's as opposed to the 2 HID lights is that I can adjust the 6 individual lights to the tops of the plants to a much higher degree of accuracy, being even more efficient in the use of the watts and lumens.

So far, I'm happy with the switch and haven't noticed any negatives. Plants are still growing and blooming, that's all I really want ;-)

Bob

I was hugely incorrect on the lumens for HID lights.

32,000+23,000 = 55,000 vs. 31,500

I still haven't noticed a problem or lack of blooms after 2.5 months. I have to assume it is the ability to finely adjust the height of the multiple CFL lights as oppossed to the 2 HID's?

Sorry for the bad info.

Bob