Supplemental led lighting and phals
 

I have six phals growing on top of a computer desk hutch next to an east facing window. The window gets pretty bright but my neighbors house blocks the morning sun from shining directly through the screened window, the sun shines directly for maybe an hour before it is directly above, at noon. I feel like the plants could benefit from more light.

For about four hours each day I take my led fixture from my planted aquarium and use it on my orchids. The fixture has 16 LEDs at 1w each and it is rated 10000k. Is this doing any good or bad to my plants? Thank you in advance for your input.

The color temp of 10000k (may not be the optimum for photosynthesis (per given watt). The color is skewed toward blue, it may contain shorter wave lengths than 400nm. But I don't think that supplemental light can be bad for plants (as long as you are not getting leaf burn, which is unlikely with 16W LED).

A Luxmeter would tell you how much do they get.

How far are they from the window? Where are you in the USA? North? South? In the middle?

For about 45° north, the distances to window for phals:
- South, one to two meters
- East/West, 50 to 100 cm
- North, bad idea in winter.
No direct light. (see below)

If you have a little bit of violet/purple on the leaves (or a lot), they have enough already.

Careful with the direct sun, touch the leaves illuminated and if they feel hot, it's too much and will burn them. If not hot, you're a happy camper.

In my old apartment, I grew my phals by the east and northeast window. East window was blocked by a tall building and provided only about one hour of direct sun.
Phals all grew fine, not great, and they even flowered. Again, not optimal performance.

I also grew a few phals under LED setup. I don't know all the numerical values regarding how much light it provided, but phals grew much better than east window and even flowered. Flower count was not much better than the one grew by the east window.

In my current apartment, my phals are growing all over the place, but mostly not too far from the south window. I have to say I am very impressed with their growth this year so far.
Leaves are much bigger than before and I'm only anticipating for the flower show. hopefully better than last year!

Aquarium bulbs likely won't hurt the plant, but may be of no benefit, either. A 10,000°K bulb will have almost no red in its spectrum, and it is skewed far toward UV.

As mentioned above, plants need both red and blue wavelengths for photosynthesis. Your light is probably helping a little. It's certainly not hurting anything.

Cheers.
Jim

That is specifically why I added red to my lamps.


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This is a bit of nit-picky comment, but for "photosynthesis", do they need both red and blue? I think that plants can photosynthesize with purely blue or red lights. That's how they obtain the curve of "action spectrum of photosynthesis" (i.e. measure the PS rate for a given single wavelength light). But for the other physiological reactions (i.e. phytochrome mediated responses such as photoperiodism), they probably need red lights.

Maybe the better way to state it is that "chlorophyll absorbs light primarily in both the red and blue ends of the spectrum".