Support lighting

I think I've asked this before, and I know I knew which plants wanted what light levels etc., but my depression seems to have burnt my memory banks quite aggressively.

I'm going to have my more warm loving multis move into my living room and for them I'm going with the same light I have in the kitchen window for my multis, a T5 865 HO-80W (Lumen 5700). I think this one works for the light hungry ones, or at least I hope it's enough.

Also, I've realized I'm probably giving my gratrix, henry etc. too little light for them to flower (they've gotten the same light as my Phals and mottled leafed Paphs). Which tubes (is that the correct term?) should I go for?

One T5 865 HO-54W (Lumen 4050) tube, or two T5 865 HO-39W (Lumen 2250) tubes?

After reading about candle foot, lux, lumen, watt, and candela, I'm just glad I didn't try to put my boots on my head when I went grocery shopping earlier.

Number of bulbs you need depends on how large your growing area is and how far away you have to put your light.

I'm assuming that you are talking about T5HO with different lengths (80W for 5', 54W for 4' and 39W for 3'). The choice depends on the shape of your grow space. If it is about 120x15cm (or 20cm), 1x 54W will work well. If it is 90x30cm area, 2x 39W will work well.

If you are going with 1 t5HO bulb, 23cm from the bulb gives decent amount of light.

Below I include a bit of technical details, but you can ignore it if you don't care.

- Paph insigne photosynthetic rate maxed out between 100-200 micro moles/m^2/s of PPFD in one experiment. (Discussed in this thread)
- 1 bulb of new AgroBrite 6400K (with reflector) gives 58 micromoles/m^2/s at 1 foot (30.48cm) away. Output seems to fall down fairly quickly with age.
- Using inverse square law, you get approximately 100 micromoles/m^2/s at 23.21cm away. (actually with reflector, it doesn't follow inverse square law strictly, so you'll get a little more than 100 micromoles/m^2/s at 23.21cm).

When the other condition isn't optimum (e.g., low humidity), plants won't be able to use all light. So you can give more distance (to cover a wider area).

Thank you so very much for answering my question.

Eh, I think that's what it means, they all are different lengths, so it must be. Alright, then one will work well since my windowsills are about that size.

I care but I don't understand it, especially since you tossed in yet another unit in your technical details. But thanks for making the effort at least.

Maybe this helps:

http://www.gpnmag.com/sites/default/files/16_TechnicallySpeaking_GPN0913 FINAL.pdf

My attempt to explain it in simpler words. lux and foot-candles are the measurement how we human eyes perceive brightness. Our eyes are sensitive to green. So we feel that a little bit of green light is brighter than lots of red (or blue light). High fc/lux means that we FEEL bright.

Plants don't see the light in the same way as our eyes. They can use any light between red and blue (but red is best for them). Photosynthetic Photon Flux Density (PPFD) is measuring the amount of light similar to lux or fc, but they are NOT adjusted to human eyes (not emphasizing green light). And the unit of PPFD happen to be micro-moles/m^2/s.

Different light sources have different light spectra, so when we are talking about artificial light, fc or lux isn't a great unit to judge the amount of light for plants. PPFD isn't perfect, neither, but it is much better than lux to judge the amount of light FOR plants.

Unfortunately, light meters which can measure PPFD are much more expensive than lux/fc meters. But you can get approximate amount of PPFD from lux/fc meter using conversion factors.

It actually did help. Thank you for providing explanations simple enough for me to understand.