Surprising discovery about my lighting

[DweamGoiL]

Very timely discussion. I was also thinking about this more in-depth recently. I use CFL's to supplement sunlight in the colder months. However, as of late, I started noticing that out of the 3 tiers of shelving I have, the lowest tier may not be getting as much light as I may have hoped.

I have had a maudiae paph for about 2 years and could not get it to rebloom. When I first got it, it came with 2 lovely buds, which very readily opened up into 2 beautiful flowers. In the time I have had it, it also did not grow much after a while. It was irritatingly slow. I then started experimenting with more powerful CFL's (particularly on the lower tier)and switching the placement of the actual plants around. That one Paph has grown 2-3 more fans in a short time and the leaves are mottling that much brighter. It no longer has that drab color it had before.

This year, I had 2 bulldog Paphs spike on the lowest tier with the new lighting. Don't get me wrong, I think reblooming the bulldogs is just that much easier, but I definitely have noticed the increase in lighting has helped exponentially.

I also decided to up the CFL on the 2nd tier because the plants closer to the back may be experiencing the same thing although I haven't noticed substantial delays just yet, but it's better to prevent problems, right? I did noticed one of my larger Phals only produced ONE flower this year. Genetically, this particular plant is not one of those with the strikingly spendiferous displays, but really...just one flower. I mean, I am in a better place now since I am getting flowers and the plants are not dying on me anymore, but it still is very much a work in progress.

Before I installed the last lighting fixture, I purchased a light meter app online and I also was shocked to see how much less light all my plants were getting. But you know how the saying goes; you live and learn so the important thing is to consider these factors and work to change them for the better so the orchids will thrive instead of merely struggle to exist. As a general rule, a light meter is a must for a windowsill grower, who plans to actually have more than just a handful of disposable orchids.

[Zabeta]

Based on this discussion, my takeaway is:

- Use the light meter, but realize that there is a lot more to it than a simple number. Wall/room color, e.g., can raise or lower how much light a plant absorbs, as can the windows/screens themselves, as can the exact placement of each leaf in relation to the sun.

- Keep high-light orchids as close to the window as possible, and low-light not so very far away.

- Perhaps most importantly, pay attention to the orchids themselves for signs of burning or needing more light.

- Yet also realize that they are adaptable and can get used to their conditions, if only limited improvements can be made (though they may not bloom if they have drastically less light than they need).

I have no desire to do complicated mathematical calculations to determine where, exactly, to place each plant, so this general set of "rules" is really helpful. And it's reassuring to know that, for many of us, even though our orchids were left basically in the dark, they didn't do so terribly there!

[mtorchid]

I've noticed something interesting about DURATION with regard to light. In winter, since the sun is lower in the sky, I get full sun coming in a south window which my Catts and Dens really like, but since the days are much shorter, the duration is less. In summer, with the sun higher in the sky, the roof overhang prevents direct sunlight from coming in but the bright indirect light is available for several more hours during the day so the orchids do just as well.

My take-away is that duration is just as important as light intensity. I would get a much lower light reading on a meter in summer as compared to the direct sun in winter, but because the duration is longer, the plants get all the light they need to stay bright green.

Even though the direct sun would give a more beneficial reading on a light meter (for my Catts and Dens), the leaves would fry if that intensity lasted hours longer during the day. If that makes sense...

[Zabeta]

Ahh, that's a really good point, Marc, and it goes back to what Sonya was saying about summertime south-facing windows. Yes, probably good not to have super intense direct sunlight all the time in the summer!

[Ray]

Originally Posted by mtorchid

I've noticed something interesting about DURATION with regard to light. In winter, since the sun is lower in the sky, I get full sun coming in a south window which my Catts and Dens really like, but since the days are much shorter, the duration is less. In summer, with the sun higher in the sky, the roof overhang prevents direct sunlight from coming in but the bright indirect light is available for several more hours during the day so the orchids do just as well.

My take-away is that duration is just as important as light intensity. I would get a much lower light reading on a meter in summer as compared to the direct sun in winter, but because the duration is longer, the plants get all the light they need to stay bright green.

Even though the direct sun would give a more beneficial reading on a light meter (for my Catts and Dens), the leaves would fry if that intensity lasted hours longer during the day. If that makes sense...

Not only is the duration reduced in winter, but the solar elevation is reduced, so the light, having to pass through more of the atmosphere to get to you, is reduced in intensity, as well.

With enough details about your latitude and longitude, you can use this University of Oregon tool to plot the sun's seasonal path.

Here in Southeastern PA, I see a reduction in duration from a max of 14 hours to a min of 9, but because the sun's elevation drops from a max of about 73° to a min of 26° in the sky, that light intensity in December 21 is reduced to only about 50% of what it was on June 21.

[mtorchid]

Great link- thanks! Re the sunlight having to pass through more atmosphere- with my local settings, high noon is barely 20 degrees above the horizon on Dec 21 and almost 70 degrees on June 21st, that's quite a difference! Would that work out to approx 50% more atmosphere on the winter solstice?