Question about lighting

[Jinh]

I have a few orchids, that based on reference materials need 2000-4000 foot candles.

I have them in a west facing window sill and have measured with a light meter. The highest reading I can get is around 2000 fc and that is in direct sunlight.

So can these orchids then sit in direct light so long as it does not go beyond their upper limit?

We have just recently replaced the windows with new double pane, energy efficient windows that do not conduct heat or cold. They seem to filter out quite a bit. I took a reading right outside the window and was getting about 9000 fc.

[estación seca]

I have read of people have problems growing plants behind energy-efficient windows. The footcandle requirements quoted for plants are typically noon measurements, and sustained levels less than this may be adequate. Watch your plants to see how they respond.

[SouthPark]

Jinh ----- also consider how much energy they get during the day. Sometimes is the light level is relatively low, then maybe that can be compensated for by having lower intensity but longer overall duration. This is assuming that the intensity isn't so low that it becomes ineffective.

[Orchidtinkerer]

dangerous thinking there southpark as some varieties depend on light hours to flower.
So you fiddling around with the light hours might achieve exactly the opposite - which I am assuming is to get the plant to flower. Even adding 20 minutes of light in a dark period can prevent certain species from flowering.
I have no idea which but that is something I want to investigate in future. I have read about this hypothesis that you can just halve the light and double duration instead - till we know more about the triggers that get every species to flower I'd be careful with this. People lower light hours in winter for a reason.
I would never try to affect intensity by adjusting light hours, light hours are to tell the plant what time of year it is. Cattleya would just not benefit as I know a lot of them are triggered to flower by light duration. Intensity then determines how many flowers it will produce. You can't go changing the one to try and affect the other.. I have read this theory more and more recently and I'm worried it will become the next orchid myth in development.

[SouthPark]

Originally Posted by Orchidtinkerer

dangerous thinking there southpark as some varieties depend on light hours to flower.

O.T. ........ note how I mentioned purposely this .....

Originally Posted by SouthPark

This is assuming that the intensity isn't so low that it becomes ineffective.

Also ------ what I was meaning was related to the positioning of the window. In particular, if the window position is such that the light at relatively low intensity has that maximum 'relatively low' intensity for very limited number of hours, then the orchid may not have enough light energy to even survive, let alone do flowering.

So my point was ------ if adequate light gets in through the window for long enough durations of time, then the orchid could survive, and even possibly flower.

And ----- the grower can always later consider usage of artificial lighting as an option - if needed, and if feasible.

[Jinh]

I was actually more concerned with not burning the leaves. Some of the culture sheets say not to put in direct sunlight.

But, for instance, if the orchid requires 3000 fc and the direct sunlight in my window is only measuring 2000 fc, is it safe to put it in the direct light without burning the leaves?

[SouthPark]

Whether an orchid gets burned or not can depend on not only what kind of orchid it is, but also on whether it is 'sun-hardened' or not.

Some orchids can easily handle direct sunlight (up to a point that is). But if those particular orchids are grown in areas where the leaves and cells haven't yet adjusted or adapted to the scorching sunlight conditions, then those orchids can burn up too ........ unless they get some sun-hardening, which is the grower allows them to gradually get more and more light over some long enough period of time. Building up. Sort of like fitness and endurance training heheh. Acclimatising.

[estación seca]

Most of the time leaf burn is due to heat from light being absorbed by leaves. If you put your hand in sunlight coming through a window you can feel the heat. Many sun blocking windows don't permit enough light to pass to warm a hand or leaf inside the window. I don't know whether your window is one of these. If your hand doesn't feel warmth from the sunlight it is not likely a leaf would burn.