8000K 0r 6000K 150W Metal Halide for Phalaenopsis?

[daemondamian]

Hi folks,
I have 4 phals that I've bought inside for the winter (here in Down Under OZ land) and will be placing them on a shelf under a 150 Watts Metal Halide light fixture.

The surface area of the shelf is 120cm long by 30cm wide and the height from the shelf to the MH fixture about 60cm.

I'm putting them into hydroton/perlite to sit in a shallow tray of water fed by a Smart Valve MK2 and resevoir above (so watering is automated), with a heat mat underneath for supplemental heating and if it reaches the MH ballast will sit under the shelf adding heat too when the lights turned on.

The MH fixture has a globe in it at the moment that produces a very blue light which is not aesthetically pleasing and is over a year old anyway so I thought I'd replace it.

I have a choice between a 6000K or 8000K globe and at the moment I'm leaning towards the 6000K partly because it's cheaper , also the store said it had a bit more yellow in it which I thought would look nicer and the 8000K has double getter technology (translate one more getter than normal ?) but I don't know if getters would actually be making any difference long term in the output of the light (that supposedly dimishes over time) or if they would just increase the lifespan of the globe while the effectiveness of it would still decline?

Without opening a can of worms I'd like opinions on which would be better or even indeed if the 150 MH will be sufficient enough light for the phals to not only grow but also bloom or too much light?

[camille1585]

I can't tell you whether the 6000 or 8000 is better, but I don think that it's way too much light for phals. If you have other higher light orchids as well, I would go ahead with the MH, but if you only have phals, they don't need that much IMO, unless you hang the lamp far above them. I'm in the Netherlands with most of my collection, but left a few phals in France in the care of the family. They are on a shelf near a north facing window (so not much light) under a 36W power compact tube. At 20cm from the tube the phals are growing, have purple on the leaves AND grew spikes. The leaves were so purple in fact that I cut back from 14h of light to 12h.

But this is just my based on what I observe with my phals, so let's wait and see what the light experts say.

[daemondamian]

Thanks for the feedback camille

I hung up the lamp and put the phals on the shelf directly under the globe.

They are on corkbark mounts ATM though the roots haven't actually attached yet because they haven't been on there long enough which is fortunate because it'll be easier having them in pots.

While they might not as close to the light when I put them back into pots I had to move them off to the side because the leaves were heating up from the globe

Whether or not they were heating up too much I don't know and I suppose I could use a fan to blow away the hot air and cool the leaves but that would lower the humidity and maybe this is a sign the light is too bright/close or they might be ok on the sides where the light sort of tapers of in intensity and I could put something else there that likes getting cooked....

Your suggestion to hang the lamp up higher could work well though I'd have to move the shelf that is above the ones the phals are on and I have no clue as to what distance from plant to globe I should be aiming at..


Actually I have a Dendrobium can't remember if it's "Uniwai Pearl" or not but it's not looking so good because it's not getting the heat or light it probably really needs with the masies and other pleuros outside and I have an Aerides odoratum out there and a few vanda seedlings that might like it also...

Ok I just measured and the distance from the shelf the phals are sitting on (without the shelf above) to the ceiling is 1.8 meters....

I'll take a photo of the setup tommorow assuming I can find where the camera is

Damian.

[markr]

The 6000K bulbs are probably best. 6700K is the most efficient for photosynthesis. 8000K will work fine though.

The primary benefit to using HID lights is that they can be (and should be) hung far above the plants - they allow you to get sufficient light to all parts of tall plants and, with Phals in particular, allow you to grow tall flower spikes beneath them. The light from fluorescent bulbs is really only useable up to about 16" from the bulb, which makes it difficult to use them on Phals with large spikes. There are ways around that of course, but anybody who has grown Phals under fluorescents will agree that it is difficult to get a straight gracefully curved Phal spike beneath fluorescents. Not impossible but HIDs make it easier.

If your Phals are hot beneath your HIDs, they're too close. Get a light meter and see how far away from the plants you can move the lights. Cooling fans are also important with HID set ups.

[Magnus A]

markr, you are wrong about the "6700K is the most efficient for photosynthesis" as the color temperature has NOTHING to do with the actually wavelength emitted from the source!

It can have a distinct peak wavelength (from Wien's displacement law) or a mixture of wavelengths that the we see as 6700K!

What the color temperature says is how we see the light! And how the color of our darlings are showing!

The sun has ~3200K
A totally blue sky ~10000-12000K
And a normal day in Europe with some cloud ~6000K
Everything depending on the distance to the equator.

For your question Damian
You found out the heating problem! The radiation from the MH will burn your leaf and you need to raise the lamp. This will lower the light and when you balance everything I think your lamp with a fan will give you a good setup!

[daemondamian]

Hi Mark and Magnus,
thanks for your feedback & info

I ended up choosing the 6000K globe and I ordered a 50W Resun heat cable (to put on a thermostat and underneath for warmth at night after the MH goes off) which with delivery worked out the same prices as the 8000K would have been.

I decided to add a compact fluorescent (I have a 45W cf on a fishtank that puts out a lot of light) with the MH and to create a wood frame lined with sealed plywood and sealing the corners/joins with silicone.

That way I can put mounted orchids in on the back and sides and fit phals and other shade loving plants at the bottom (lining it with pond liner) to be fed with a smart valve.

I'm not sure yet at exactly what height I will have the top of the box and the lights inside.. I was going to build it almost right up to the ceiling but I'm not sure if I'm putting a resevoir tank on top or not or to the side of the box.

Anyway, I'll take some photos and start a new thread when I do but I'll come back to this one and add a link to the new one.

Thanks again
Damian.

P.S. I considered putting a front/door with plastic or glass to hold the humidity in but I have two fish tanks right next to there and am getting 50-65% humidity levels in that spot and temps around 20 degrees.. I found one of the phals has started a spike already and I can't wait to see how they'll react to their new conditions. Hopefully I'll get some real nice tall spikes!