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Hello all,

Firstly I would like to ask which is more efficient: to put lights near to the plants or not? I have put my lights in minor distance of 70 - 80 cm... (two fluorescent lights, 18w each... one of them is common and the other gro-lux...) Any recommendations...?

Secondly I would like to know how long does it take for the s/h material to dry out in a 12cm pot of yours? (approx.) Mine usually dries out the next day to almost all of my plants.... Does this mean I have to water two or three times a week...? Imagine that it's already winter here... what's going to happen in the summer...?????? Will I have to water daily...??????? Please help...

Any help. suggestion etc is welcomed... and appreciated...

Thank you in advance...Thanasis... :0


Well-Known Member
Jun 9, 2006
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Elk Grove, CA
I'll let someone else that grows under lights answer your lighting questions.

To answer your question about the s/h drying out. Your resevoirs are completely empty in a day? Maybe you mean the top layer seems dry? I do have some plants that really suck up the water. But, you really shouldn't be seeing the resevoirs empty out every day with most of your plants in the winter. If you're meaning the top layer seems dry....well, that's how s/h works, on a moisture gradient going from wet at the bottom to less wet as it wicks up to the top.

Eric Muehlbauer

Put them as close under the lights as possible...18 wt fluorescents are not very bright, and gro-lux is much lower in light output than a normal fluorescent. Enjoy them though! Eric


18 watt bulbs x 2 at a distance of 2-2.5 feet (roughly your 70-80 cm) from the leaves is almost like growing in the dark. Unless you have supplemental light coming from a window etc of course. "Low light" plants require 1000-2000 footcandles which is barely obtained from 4 four foot long fluorescent (either T12 or T8 bulbs which are between 32 and 40 watts *each*) hanging LESS THAN 10 inches from the leaves- 6 inches is even better. Light decreases DRASTICALLY as distrance from the bulbs increases. Mathematically, 1 over the distance squared 1/(distance)^2. In human terms, if you measure 2000 fc at your bulb, 2 feet away the intensity is 500 fc per 2000fc/(2)^2=2000fc/4=500fc. generally not enough light to bloom a flowering plant. Anyway, the wattage is not the crucial factor- you want to know output either in footcandles, lumens, or lux (I can almost guarantee you unless aliens with some awesome technology made your 18 watt bulbs that they are less than 1000 fc each). Second, you want to know the spectrum of the bulb(s) to know whether to use one bulb instead of or in addition to another. Your plants will do okay for short periods to display them while in bloom etc, BUT I doubt you'll be able to rebloom them if that's your only light source.


Well-Known Member
Aug 29, 2006
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I agree that it is too far. Now I use 30 watt bulbs to flower phalaenopsises in January and I keep the plants about 12-20 cm from the bulbs. You can use light meter to check how many footcandles at what distance your lights give to the plants.


I put together a light a few months ago w/2 105W CFL's to replace a 400W MH setup. Here are some of my measurements in FC's.

400W MH..................2-105W CFL
12" 1000 fc 12" 1600 fc
24" 600.................24" 800
48" 200.................48" 400
The color-temp is almost the same. Right now I use the light for a staging area for plants in spike,sheath and bloom. It gives off no heat and half the cost to run. Hope this can help someone. Jim.


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