correct lighting for mini phals

[Lucian]

Hi,
We are trying to work out the lighting for our mini phals.

We are growing indoors under lights. Our set up is a 4ft x 18in shelves with humidity trays. The tops of the trays are 18in from the lights and the phals are 11in from the lights.
We have two banks of two 48in x T12 Daylight 40w flourescent tubes although we only have one bank in use.The lights are on 12hrs daily and supplemented by normal indoor daylight.

We also have spare T8 fittings we could use, if that would be better.

We are trying to juggle with lighting and heat.

To test the lighting, we have an Environmental Concepts Plant Light Intensity Meter. With the switch set to Flourescent, the meter is reading
500fc at plant height using one bank of 2 x 40w T12 Daylight tubes. Temperature is 79f and humidity 59%

500fc seems way too low so, should we look at the Sun reading 5000fc?

We have tried different permutations of lights but the more tubes we add, the temperature increases into the mid 80's and humidity decreases into 30's. We have noticed burning of the leaves with more lights.

As it stands, our plants are looking good in as much as the leaves are glossy, there is plenty or root growth and we have had an abundance of keikis.

Our questions are these.

1. is our current set up, light temp humidity, causing too much keiki growth and will this affect spike growth?
2. what should be the correct fc for phals? The readings are either too low (500) or too high (5000)


We are moving the shelves to another room this weekend so if we need to make changes, now would be a good time.

thanks

[naoki]

Lucian, if you have 32W T8, it is probably better to use T8 because it is more efficient. I think it will give similar output as 40W T12 with lower electricity (in theory lower heat, too, but I've never measured the temp fof T8 vs T12). So with T8, you may be able to put the light closer to the plants. With T8, I can put phals within 5-6".

The other thing is that you could increase the duration of light from 12hr to 15hr or so. I forgot the details, but I calculated the approximate equivalency between 15hr constant light vs natural day light. For example, if a book recommend 1500fc peak intensity in greenhouse, you can get similar amount of cumulative light with 1000fc of constant florescent light. If I find my old posting, I'll make a link. I don't grow hybrids, but for species Phal, I'm using about 900-1000fc, 15hr/day.

I'm not sure about the answer to your 1st question. But for some highland/lower temp phal species (e.g. P. pulchra), I've heard that heat could cause keiki instead of flowering (but some other people says this is not the case). Are your orchids flowering with 500fc? It seems a little low-end, but if they are flowering ok, you probably don't have a problem.

With regard to leaf burning, do you have enough air movement to reduce overheating?

With regard to humidity, Phals are CAM plants, so night time humidity is more important.

[naoki]

OK, here it is

Message #24 to #28 in the following thread:

http://www.orchidboard.com/community...enopsis-3.html

has links to guesstimate the equivalency between T8 and natural fc.

[Lucian]

Hi Naoki,
This weekend we moved our shelving into another room where we should be able to control the temperature a bit more, particularly the night temperature.We changed to T8 lights and increased two hours. We will probably lower the lights closer to the plants. It is just going to be experimentation. Our biggest obstacle was probably not having a decent temperature drop at night.

We will keep you posted on how it goes.

Thanks Lucian.

[naoki]

Lucian, I've never figured out the reason for temperature drop at night. I've seen many books emphasize its importance, but I haven't seen a satisfactory explanation why it is beneficial. Does anyone know about this? One reason I could think is that relative humidity at night is actually the important part. Lower temp at night will cause the RH to go up. CAM plants like Phals are likely to do gas exchange during the night. So they may be able to open their stomata more freely if RH is high at night. Anyway, I hope your plants like the new location!