How bad is night time light coming from outside?
 

In the many discussions about proper lighting for orchids, I have never seen this question addressed. I am a windowsill grower. The best -- and really only -- window I have in my home which would be appropriate for orchids is a south-facing window in my kitchen/dining room. The window itself measures approximately 65 inches wide by 45 inches tall. On the dining table in front of this window is where I keep my small collection of orchids.

I have wondered for a while now whether the security light on the front of my garage is detrimental to the orchids. The garage is detached and sits slightly back from this particular window, but the light, which comes on at dusk and goes off at dawn, definitely illuminates this kitchen at night. My guesstimate is that it is 25 feet from the window. The light is enough that I could come into the kitchen to get a glass of water, etc., without having to turn any lights on. I could hold something like an envelope up, facing the window, and could read it, albeit not easily. I guess it could be compared to the orchids being under the light of a bright full moon, 365 nights a year.

The window has some lace-type curtains that let in enough light that I usually don't bother opening them in the daytime. They don't cover the whole window but rather the bottom half, what they call a tier. There is also a valance which partially covers the top portion of the window.

I have a variety of orchids, a few phals, a couple oncidium types, a small cattleya, and a paph. The ones that like more light get put the closest to the window, and the lower-light ones, like the paph, I position behind the bigger ones. All are growing reasonably well for me, but I'm having trouble getting anything to rebloom. (Well, except for one phal that is currently putting out a weird spike -- a topic for another thread.)

Anybody have any thoughts on whether this night light is a serious enough issue that it could be affecting the well-being of my plants?

It probably isn't enough light to worry about. You compare it to full moon light, which is less than 1 footcandle. You say you can just barely read by it with difficulty, also indicating less than 1 footcandle. Certain very photosensitive plants requiring a certain duration of darkness to flower might be inhibited by that, but that does not include any commonly grown orchids. And it isn't enough light to prevent the physiological "rest" that plants need to stay healthy. I don't see how it could be a problem.

I agree, we have night lights on and I've never noticed a problem.

Thanks to both of you for your replies. That does put my mind at ease. I'm sure it's a fairly common problem. In my case, I live in a semi-rural area and this is a light on one of my own outbuildings, but I know other folks must have to deal with street lights, parking lot security lights, or lights on inside the house for various reasons, etc.

Of course, the obvious solution, if this was causing a problem, would be to install some type of darkening shades or curtains, but I'm reluctant to do that because this is my kitchen/dining room, it's one of the largest rooms in a very small house, and I don't want to make the room any darker in the daytime. I'm afraid even shades that are fully retracted will cover part of the window near the top.

Last night, after it got dark, I had a chance to observe the nearly full moon outside this window, perched in the sky above this light. From the vantage point of the plants, the moonlight would be coming through the window where it is clear glass, not covered by the lace curtains, and the garage light would be shining through the curtains, which diffuses it somewhat. Seeing them side by side like that, I would say the garage light was noticeably brighter than the moon, but not by a large amount.

Thanks again.

Have you ever considered solar shades? They roll up out of sight. They are enough to block hot sun, or in this case a yard light. In the morning, you can roll them up. We are in a fairly rural area also. We have 'Happy lights' on the garage to no ill effect.

I have thought about the various types of shades that are out there and what exactly I would do if I learn that the night light is detrimental in some way. I have a variety of window coverings in the rest of my house, roman shades, wooden blinds, cellular shades. All of them do take up varying amounts of space at the top of the window, even when completely in the "up" position. There are ways around that such as doing a high outside mount, etc., but I'd rather not change it at all if it's not really necessary. I kind of like the way it looks as it is.

Anybody else want to weigh in? Do you grow and bloom your orchids successfully in spite of some incidental light they may receive overnight?

There are only some orchids that are extremely sensitive to photoperiod (daylength). For example, there are some Cattleyas that are deliberately inhibited from blooming in a greenhouse with a single incandescent bulb turned on in the area. Other orchids are not so sensitive and may be triggered to bloom more by temperature changes.