FYI: Light Measurements under T5 lamps

[kavanaru]

I just updated orchid lamps from T8 to T5, and went for a larger set. Obviously, I understimated the power of these lamps and need to find a quick solutuon, before my plants get completely BBQed. The problem is not the hight output of the lamps, but also the increased temperature (I have masured 28°C = 82K) and the leave of some plants are really too warm...

Light measurements:

6x T5 à 80Watts each (supplemented with individual reflectors - one per tube) - 6500K/3000K ratio 2:1

3 inches below: 5973 Fc
6 below: 4600 Fc
9 below: 3500 Fc
12 below: 2400 Fc
15 below: 1570 Fc

4x T5 à 80Watts each (no individual reflectors) - 6500K/3000K ratio 3:1

3 inches below: 3900 Fc
6 below: 2600 Fc
9 below: 1500 Fc

all meassurements done below the central part of the lamps!

[Ross]

That sounds about right. I recently measure 4600 foot candles at the soil level of my "garden" and approx 90 degrees F. I put a large fan on the setup and temps is down to ambient basement temps (approx 65-70 degrees F).

[kavanaru]

so, you think I should leave them this way, but just add a fan to the set up? I am afraid of burning the plants, especially the miniatures...

and, what do you think about the photoperiod? I currently have 12/12, but in summer I use to have 14/10... wouldn't that be too much with these lamps?

[Ross]

If you can do it, I think you should lower the illumination to the amount the plants desire. Either raise the fixture or lower the plants. Just watch the leaves of the low light plants like Phals and Paphs or Dracs. I use 12/12 right now and increas to 14/10 just as you are planning. The only plants I have under the 8 tube fixture are raddish, spinach and lettuce and they expect really high amounts of light. None of the orchids are exposed to more that 1800 foot candles. You can also get some white cloth and hange over the plants that need more shade. Don't close off the light fixture, it will overheat. Get lots of air movement between the lights and the plants. It'll help warm up the room quite a bit. Hope this helps.

[gmdiaz]

Can you lower the shelves or raise the lights, as Ross suggested?

While you figure out what to do. . .try to add some sort of shading between the lights and the plants.

I had two four foot long T5's. . .individual fixtures with little reflectors on each. Two was too much. And I could really see the plants starting to stress. So until I had a moment to remove one of the fixtures and rearrange things a bit. . .

I ended up using some plastic panels (used for florescent lights) hung beneath the lights with some wax paper on top.

It was not a pretty solution but luckily it just had to work for a while. I've since gone to one light on that top shelf. And this is for my highest light plants.

P.S. Thanks for those light measurements!

Good luck, buddy.

Editing to add: You do need fans! I think they're necessary. . .and so good for your orchids in so many ways.

[kavanaru]

my problem is that I cannot move the shelves anymore... I think the idea with the white cloth is a good one, addinde also some extra ventilation... First I need to take off the reflectors, as i know that would reduce the light considerably...

I have not use fans until now, because I have enought air movement here, and in two year it has worked perfect... but let's see...

[LinhT]

How far do you have your medium light plants from that 6 tube fixture? I vote for the fan too! I have a fan blowing across the length of my 4 tube 4 ft T5 fixture. On mine, even at 2 feet below the tubes, I still measure a little over 1000 fc in the middle of the bank. The plants that you keep well watered throughout the year are probably ok but if your neos are in their rest period and you're trying to decrease watering to keep them on the drier side, some of the more finicky thin leafed ones will show LOTS of purple spots and turn yellow green at around 1300fc 12/12. Just my

[gmdiaz]

Originally Posted by LinhT

How far do you have your medium light plants from that 6 tube fixture? I vote for the fan too! I have a fan blowing across the length of my 4 tube 4 ft T5 fixture. On mine, even at 2 feet below the tubes, I still measure a little over 1000 fc in the middle of the bank. The plants that you keep well watered throughout the year are probably ok but if your neos are in their rest period and you're trying to decrease watering to keep them on the drier side, some of the more finicky thin leafed ones will show LOTS of purple spots and turn yellow green at around 1300fc 12/12. Just my

That's exactly what I am noticing too. . .the Neos are a little sleepy and the light is too high right now but they LOVED it during their active growth and flowering period.

[kavanaru]

Actually, my Neos are outside on the balcony without extra light (closed balcony - Temps never go below 5°C, normally stay aove 10°C) I have reduced watering already, but somehow some of them do not understand what they should do, and are even growing new fans Anyway, they stay outside...

[LinhT]

Originally Posted by kavanaru

Actually, my Neos are outside on the balcony without extra light (closed balcony - Temps never go below 5°C, normally stay aove 10°C) I have reduced watering already, but somehow some of them do not understand what they should do, and are even growing new fans Anyway, they stay outside...

You're so lucky, Ramon. I want to move to Basel.