Do standard room lights help if left on?

[RosieC]

I don't grow under lights as such, I try and make do with daylight on the windowsills. But at this time of year it's so dark and dingy every day I worry about my orchids, my greenhouse is still pretty bright with light from all sides, but the windowsill ones don't seem to get much.

So I'm just wondering if having the room lights on helps in any way, or is it the wrong sort of light. I mostly have compact florescent lights in the centre of each room. Mostly nowhere near the orchids, but the orchids are lit by them.

Anyone know if this helps even a little

[katrina]

It'll make the room brighter but chances are it won't help the plants all that much...especially if the plants are on the windowsill and the light is on the other side of the room.

On the other hand...if the bulbs are "daylight" or full spectrum bulbs (even lower wattages) and the plants are right under those bulbs...then, sure, it can be helpful to some extent. It won't bloom high light plants...but it'll bolster the lower light plants. The longer you can leave the lights on...upwards of 14-16hrs...the more benefit you'll see. When dealing w/lower wattage/less intense bulbs...the longer run time adds impact by being cumulative in their effect.

[RosieC]

Thanks Katrina,

That's about what I thought. I'm mainly concerned with stopping plants going downhill as a result of several months low light through the winter. Winter is always my troublesome time of year for many reasons, and I think the low light levels are just part of that.

[Laserbeak]

Probably not, in fact it could be harmful if your plants need a dark period to thrive. The number of photons reaching your plants are not going to be enough to have a significant effect on photosynthesis, but could interrupt the processes some plants need to do in the dark.

[RosieC]

Thanks Laserbeak,

I wasn't thinking of day & night, just more than only when I need the light. But I thought it was probably the case as you say that it wouldn't provide enough photons to make any improvement so I'm not going to waste energy on leaving them on.

[Ray]

I think they will be of no value whatsoever, simply because they are probably too far from the plants - remember the inverse square rule. The human eye can adjust, so perceives the light as bright, but chlorophyll has no such adjustment capability.

I measured the output of a 24w, 2' T5 fluorescent fixture with a polished aluminum reflector. The intensity 1" from it was 2000 fc, but 12" away had dropped to only 400. How far are the plants from what wattage bulbs, and are they bare or shaded?


Ray Barkalow
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[RosieC]

Thanks Ray, that makes sense. I had not thought about how the eye adjusts so we perceive it lighter.

In my living room they are probably about 2m from the lights, there is 5 x 12W compact florescents in a single light fitting (a second fitting the same on the other side of the room). They are shaded with frosted glass shades.

This room is pretty bright for human perception and the center of the room between the two light fittings is a great place for photographing the orchids, but I think you are right that it won't be enough to help the orchids.

[LovePhals]

This is very informative! If you wanted to add some light you could put a lamp with high wattage in close proximity to the plant without the shade and add good light instead of grow lights.

[Paphluvr]

Originally Posted by RosieC

I don't grow under lights as such, I try and make do with daylight on the windowsills. But at this time of year it's so dark and dingy every day I worry about my orchids, my greenhouse is still pretty bright with light from all sides, but the windowsill ones don't seem to get much.

So I'm just wondering if having the room lights on helps in any way, or is it the wrong sort of light. I mostly have compact florescent lights in the centre of each room. Mostly nowhere near the orchids, but the orchids are lit by them.

Anyone know if this helps even a little

I think it might actually be a detriment if left on too long. Many plants use photoperiodism (changes in the duration of daylight) in order to initiate bloom. Of course, at the distances you're talking about, the intensity is minimal so I'm not sure how much photoperiodism would be effected.