Leaf Burn under T8's? - Orchid Board

josterha · #1 08-06-2009, 11:18 PM

Hi everyone,

I am very excited. I have just finished my new indoor growing area for my orchids. I have a collection of about 30 phals and paphs. I am using galvanized shelving from IKEA together with 4' T5 fluorescent bulbs. I have Phillips "deluxe sunlight" bulbs and so far am very happy with the light. It seems pretty natural and doesn't cast a sickly pall on everything. I have about ten times the space of my old light table. Anyway, my questions are:

1. Do you think that I can burn the leaves with these lights? I am getting between 600 and 1,000 FC at various places on the shelves. I know this sounds like not a lot, but it really beats my old system, in which I only got a maximum of 68 fc!!! So I'm getting more than 10 times the light intensity than previously. Believe it or not, I actually got a number of Phals to spike under this light, and at the end had a first-time paph spike!

2. If these orchids are tropical, what sense does it make to vary the "day length"? I mean, in the tropics the days are basically 12 hour light, 12 hour dark. Also, these orchids probably have at least intermittent shade from canopy trees all throughout the day.

I am still new at this, and I would appreciate any guidance.

THANKS!
John

Blueszz · #2 08-07-2009, 07:04 AM

Hello John

I recently started growing under lights (PL fluorescent lights).
Anthura in NL sells young plants to nursery's and they have sort of a handout online which might be interesting to read: http://www.anthura.nl/uploads/downlo...ants%20ENG.pdf

It discusses Lux, feeding and day lenght for optimum results.

According to this handout, 1000 fc would be a lot for plants in spike. During growing phase they recommend up to 600 fc but they can do very well with less.

To get them used to more light you can shade them with a cloth over the plants, but leaf temps seem to get higher this way... this according to studies from the University in Wageningen NL.

Nicole

calvin_orchidL · #3 08-08-2009, 10:07 AM

Generally the rule is that catts/dends need upwards of 2000FC whereas phals can be happy with 500-1000. However, it's a little misleading because typically that number corresponds to maximum light intensity during the day, which as you mentioned varies in nature. You can get away with less light for longer in some situations.

In that handout, they mention lux (which is actually what we should be using to discuss light

) which is roughly 1/10 one footcandle. They go up to 12000 lux (1200fc) for their 'finishing' phase

josterha · #4 08-08-2009, 11:17 AM

Thanks, Calvin and Nicole! That's a good resource. Actually, lux is easier for me to take measurements in, since my light meter is actually in lux, not footcandles (as I suspect most other people's are as well). I will really study this sheet.

Blueszz · #5 08-08-2009, 01:06 PM

lux/10=fc, that is what I do to when I measure light, but it would be better to divide by 11....
If you are online and want to calculate how much lux = fc you can use Google. Type for instance: "convert 5000 lux to fc" and search.

Nicole

Undergrounder · #6 08-20-2009, 11:42 AM

Yes! It depends how mature they are and what type they are but it is easy to stress out Phals using just T8s and especially T5s. At about 1000fcs for the whole day you're likely to see a lot of red and purple leaves even on mature plants, although probably not burning.

Small Seedlings prefer about 200 - 300fcs which is basically just a single T8 at close range. Established seedlings will take up to about 500fcs (two x T8s at close range) and adult plants will grow happily from 500fcs+

And then when you want to initiate spikes just increase it up to 800-1000fcs for a few weeks.

mayres · #7 08-20-2009, 01:38 PM

In my experience using T12's - which emit approximately 1000 fc at the surface of the tube - I leave them on about 15-16 hours per day with great results for phals. I also have a T5 that I have found will even burn/over-light catts & oncids let alone phals - if placed too close. A significant difference.

Burgos · #8 08-20-2009, 06:28 PM

hi, i just wanted to ask how far are the plants from the bulb? and how many bulbs do you use? for how many surface?

i hope you can help me with this, im a newbie in light

Undergrounder · #9 08-21-2009, 07:32 AM

Quote:

Originally Posted by Burgos

hi, i just wanted to ask how far are the plants from the bulb? and how many bulbs do you use? for how many surface?

i hope you can help me with this, im a newbie in light

All plants i grow on shelves that have a growing area of 100cm x 45cm.

If you leave the T8s about 25cm above the plants, one tube is good for seedlings, two tubes is good for larger seedlings, three tubes will grow mature plants and 4 tubes will grow large established plants.

But because the light distribution can be very uneven (especially with just a single tube) and changes so much over time and with varying height, i would reccommend buying a light meter and work out the appropriate number of tubes/height to get the FC range you're going for. If you're just guessing then you don't have a measure to fall back on and adjust if things go wrong.

P.S. I forgot to mention these levels are with the bulbs in a reflective box that i painted white so the light reflects down from the top of the tube. If you do go with T-tubes make sure you're reflecting the upper light, the difference is very significant.

Burgos · #10 08-23-2009, 04:24 PM

thanks a lot for the answer Undergrounder, i was thinking about a setup with 2 fluorescents. it´s for big plants, but it would complement natural light. currently im growing them without any aritificial light, and getting good results in my opinion.

by the way my phal doesnt get direct sunlight and its leaves are purple, so i think lights would be a good choice for winter when light is reduced here.

and how much watios are your bulbs?