How much PAR for high light orchids
 

I am building a large terrarium with lots of branches for epiphytes. The LED lights I'm liking are measured in PAR out put & all the orchid lighting needs info I find is in foot candles. If a high light orchid wants 2500-3500 FC of sun light. How much PAR of constant light level would be needed.

Thanks
Jim

Foot candle (FC) is a measurement of intensity, PAR (Photosynthetically Active Radiation) is not, PAR simply refers to light with a wavelength between 400 nm to 700 nm. Photosyntheic Photon Flux (PPF) measures the intensity of PAR light. Here is information for converting between PPF and FC.

Conversion - PPF to Foot-candles

So, according to those tables, 2500 FC of sunlight is equivalent to a PPF of 500 micromoles per square-meter second of PAR light.

I actually had seen that formula before & came up with 500 to as much as 700 PAR. But when I talked to some orchid people & the lighting manufacturer I like they seem to think that much light was not really needed.

The 2500-3500FC being pretty much the brightest part of the day. Then there are the cloudy days & shadows part of the time. Terrarium lighting being constant all day every day a straight conversion isn't what is really needed.

I was hoping someone here who has grown high light loving orchids in a terrarium & knows what PAR they have in their tank could help me get what I need for my tank. Lights are so expensive for a big tank I don't want to buy more than I need & don't want to have too little either.

Does Anyone who grows high light loving orchids under lights know what PAR reading/level they have?

I was at a talk last Sunday on growing under lights and PAR wasn't mentioned at all.

Guidelines were given though:
if you have 2 fl tubes, best to have 1 cool white and 1 warm white
Bright light plants/seedlings - 2,500 to 3,000 lumens
Shade plants - at least 1,500

My plants vary in distance from the lights. In a terrarium I don't know if you can be as flexible in moving plants around.

I successfully grow a mix of plants ( orchids/gesneriads ) using T5s - to blooming - and turns out warm white fixtures. I will replace one bulb with a cool white. The speaker did say that if you are happy with what you have, then don't change. Problem is that how can you be happy if you haven't experienced both cool/warm ? Who knows, you could be happier. :lol:

Hopefully you can do the PAR conversion !

How much PAR for high light orchids
 

I'm familiar with par from the aquarium plant world and I'm familiar with FC from the orchid world, but I'm not sure exactly how they coincide. I would recommend going I the AppStore of you have an iPhone and getting a light meter app. I can't remember the name of the top of my head, I'll get it and then post it in a minute. It's free and pretty accurate. I would say get a light that is good for your other needs and then use the meter to measure the FC in different spots, you can place plants according to the readings in different places.

EDIT-it's called LightMete and the company is WhiteGoods. Should be free

Not PAR. PAR does _not_ specify light intensity. PPF specifies light intensity and even then you need to know what units are being used; usually PPF is specified as micromoles per square-meter second but it could be specified in other units. Anyone who uses PAR thinking it specifies light intensity does not know what they are talking about.

That's what Ive been trying to say. The ratio of par to visible light in sun light is a constant (I believe) but the radio of par & visible in artificial lighting can vary greatly. LED lights especially can vary a great deal depending on what bulbs they use & which part of the spectrum they produce.

I understand few if any in the orchid world use par as a rule. So if there is not an answer for my question here OK. PAR is still the best way to know what amount of usable light is being produced.

Then there is the constant artificial light vs changing light levels in nature thing to consider.

I had a reef tank once & grew many kinds of corals. There were some general guid lines on what par the different types of coral needed. It's looking like those type general rules have not be worked out for orchids ATT.

If so it's a shame because it saves a lot of trial & error

Orchids aren't nearly as picky about their lighting as reefs and aquatic plants.
Which I think is why your not finding anything. Because it doesn't really matter in most cases.

Sent from my SCH-I535 using Tapatalk

So it looks like the short answer is No, no one knows what PAR level they have in the setup?