Confused about light - how much for how long?
 

Hi,

I was looking at the forum on growing under lights, and now my head is spinning. I'm trying to figure out if my orchids need more light. I grow in front of a window with a 25w flourescent terrarium bulb about a foot away from the cattleyas.

You know when you read that this type of orchid needs 1,000 fc, and this other type of orchid needs 3,000 fc, etc?

Does that mean so many foot candles over the course of an hour over the course of a day or whatever? Ahhh so confused.

I got a light meter app for my phone, which is probably sort of accurate, so I know the flourescent emits about 800 fc steadily for about 16 hrs a day (I turn it on when I wake up and off when I go to bed). The light from the window, however, is much weaker, more in the range of about 100 foot candles at the brightest (so few! Why aren't my plants dead??) and, of course, varies throughout the day.

So, logically, I'm thinking that I need more supplemental lighting for my orchids, BUT, almost all of my phalaenopsis are currently spiking, all of my oncidiums have new growth, and one of my cattleyas is growing two new... pseudobulbs? Also, its leaves are tinged red... so that's a good sign, right?

I just want to be sure I'm not somehow forcing my orchids to live in sad low-light conditions.

Opinions? Of course, I could always wait and see... but one of you may know the answer! :D

I've included a photo of my setup (at night!) for good measure.

Trust the plants, not the phone. Phone light meter apps are mostly unreliable. People handle light issues two ways: they measure, or they keep pushing light levels on their plants until they show signs of high light.

You can buy an inexpensive light meter intended for photographers. This will work better than any phone app. The app won't work even approximately unless the developer has access to the output specs for each phone's camera sensor. This doesn't happen.

When you read culture sheets that give light levels, it is usually the peak the plant should see.

There is an article HERE that explains how that translates to the use of artificial light.

Thank you for the replies! I think I'm going to invest in a real light meter.

Also, very helpful article. Thanks :)