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I’m trying to grow some coffee plants inside and I have no good place where they get all their needs so I want to start with a blank slate and control everything myself.

I know coffee plants like shade and not a lot of natural light but how does that convert to grow lights? If I pick up some blue red grow lights, how long should they be on? A couple hours to simulate sunlight or longer?

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That is an interesting question. Shadow is everything that is not in direct sunlight (obviously). So maybe you could measure the amount of light in shadow outside? I would not just give it bright light for a few hours and leave it in darkness the rest of the time. That is not the same as standing in shade.

A quick google search tells me, that e.g. in California a bright day of sunshine means a PAR of about 1000 micromoles. But finding a value for shade is much harder. I couldn't find anything useful right now. My guess is, that on a bright day, you might have around PAR 200 in the shade. You can achieve a value like that with some low power LED. Like a marshydro eco 49 with a proper distance to the plants. Keep the light on for 14 hours a day (approx)

You will probably need to do some experimentation yourself on this. Regulate light intensity by moving the lamp closer or further away from the plant. (Or have the lamp fixed and use several plants that stand on different heights)

If you like to do some reading, maybe this will help: http://eduem.uem.br/ojs/index.php/ActaSciAgron/article/viewFile/941/470 I have only slightly read it right now. It looks like its about photosynthetic reaction in coffee leaves and according PAR values. Should get interesting at page 334

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  • Thanks for that (and I am excited to read the paper). I guess I didn’t mean to keep it in darkness for the remaining time but I also didn’t think about how much light they still get in shade, especially for a plant native to climates near the equator. – alnair Feb 14 '19 at 19:32
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My comment's too long So: Basically agree with most of what elPlloLoco says. Here's a little more info:

@elPlloLoco: "1000 micromoles" technically that's 1000 microEinsteins; an Einstein being a mole of photons: . No complaint here, it's just one of my favorite units, and I'd like to see it used more. I run my winter growth chamber at about 500 µEinsteins (half sun), and it works pretty well for full sun plants. Temperature is a problem when you get it that bright. 2 foot by 4 foot using 5 2700°K screw in fluorescents, and a 100 watt HP Sodium lamp. Cooling fan is essential. The shade plants like to be under the top wire shelf, so probably somewhere around PAR 200-250, as elPll says. When buying lamps, people tend to emphasize blue too much. 400nm-700nm gets both photosystems nicely: All the extra low nm blue does (Hg line) is heat and dehydrate things, and burn your leaves.

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    Srsly? It's really µEinsteins? That's so cool. I will call it that from now on. – elPolloLoco Feb 14 '19 at 7:19
  • Thanks for the info! Never heard of Einstein as a unit before. – alnair Feb 14 '19 at 19:29

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