Distance between light fixture and plants .....

[NeoNJ]

I have 2 CFL clamp-on light fixtures. I have my Brassavola nodosa hanging about 8-inches from the light fixture. The leaves are turning yellow and falling off...

I read on some websites to place the plants 4, 6, or 8-inches from the lights. I kinda find this to be just a little bit to close --- this has already caused my Sophronitis cernua and now my Brassavola nodosa to turn yellow and drop leaves .........

I'm using 100w 6500k spiral Daylight CFL bulbs.

[Brotherly Monkey]

the problem is that you can't give out solid rules on lighting placement because a) variety in bulb intensity b) various plants having different lighting needs c) culture and health impacting how much light a plant can take.

There is a way to check foot candles with an slr, if you have one handy. If not, I would move the light 2-3 feet away, and slowly acclimate it to the point where you start getting some reddish coloring on the brassavola. For any other plants, you'll have to research their specific needs, and work from there

PS those 100 wt spiral lamps are pretty powerful, so it might be a better idea to go 3-4 feet

[NeoNJ]

Problem is the Brassavola isn't getting any red coloring --- its going directly to yellow ! However, the Neofinetia falcatas which are below the Brassavola are getting redish coloring on their leaves.

Since I've had the Brassavola nodosa for like 7-years and it's never bloomed, I finally figured it's the light....
and even though it Summers outdoors, the plant still hasn't bloomed......I just can't bring myself to part with this orchid, I'm determined to Bloom this Brassavola !

[Brotherly Monkey]

well I imagine that it's getting roasted at the moment, because it didn't have time to acclimate to the light level, and you have a pretty powerful bulb on it, that would be too strong at that distance, regardless of acclimation time

[camille1585]

I agree, it's really hard to say what distance to have between the plants and lights. And your CFLs are putting out a lot of light. I read in one of your other threads that apparently you have a light meter. What kind of readings are you getting at 8in from the lights? That's your best bet for figuring out what's ideal. I'd also tend to agree that you might have taken the Brassavola from too little to too much without giving it time to adjust.

I don't have a light meter, so when I got my lights I hung them at what I thought was a reasonable distance, and went by leaf color over the following weeks to judge what was good.

[NeoNJ]

I don't know, Camille, I just can't work without a LIGHT METER - I don't like estimating, not when it comes to growing and blooming Orchids.

My Light Meter reads a pretty constant 5000fc of Light - and thats for the orchids actually sitting on the windowsill - the light fixtures are a good 3-ft above the windowsill.

I lowered the Brassavola to 16-inches below the light fixture. It was getting in excess of 6000fc of light.

[camille1585]

That's probably too much, maybe even at 16". Time will tell though. Keep in mind that in the wild, a plant which is said to need high light (4000fc as an example) is not getting that all day. There will be a period during the day when it does get that, but a lot of the light will be much lower as the sun is rising and setting. So on average the fc the plant gets is much lower than 4000 over the course of the day. When growing under light we give them the same hours of light as they would get outside, but the difference is that the amount of light is constant. So you need a much lower light output to achieve the same results.

[camille1585]

I looked up Brassavola nodosa in Orchidwiz for you, and this is what it says about light for this plant:

Light: 2500- 3500fc. Plants may well be able to tolerate higher light levels, if they are introduced gradually. When light is high, high humidity and strong air movement must be provided. [...]

Hope that helps a bit.

[Brotherly Monkey]

1) what type of light meter do you have?

2) if the 5000fc is an accurate reading, then it will still be too strong, imo, even with a good air current

[NeoNJ]

I use Fans plus a Humdifier, that essentially run 24/7. Keep in mind my growing area is Small - it is limited to one windowsill which is approx. 4-ft. x 4-ft. The recommended distance between the light fixture and the tops of the orchids is 24-inches for Moderate Light orchids, and 12-inches for High Light orchids.

The light fixtures are currently approx. 35-inches from the tops of the orchids on the windowsills. So, at this distance I don't think the orchids are getting too much light - BUT the light meter is infact registering 5000fc
at a distance of 35-inches.