Light levels Experiment

[Kerry]

Hello all

I have been looking up info on light levels, as I suddenly became a bit concerned about whether or not my plants would be getting enough light where I have them. This was probably prompted by my somewhat foolish behaviour of buying a couple of catts and vandas when I have no idea whether they would like my house.

Anyway, I have borrowed a good light meter from work and I intend to do some regular measurements over the Easter weekend (when I am in) to see what sort of light levels my plants are getting in different areas. The forecast for this weekend is for both sunny and partially sunny days.

One of my cats (feline kind) woke me up at 7.30am with some gentle head butting, so that's when I took my first reading. Bear in mind, the light meter I am using measures in Lux, and that 10 lux is approx 1 fc. I am trying to measure with the light meter facing upwards (horizontally), to approximate what light falls on the top of the leaf, rather than facing outwards vertically to the window (which causes a super jump in levels). If I am wrong and should be measuring vertically not horizontally, let me know.

I have read quite a few threads that refer to it being the amount of light in total over time that is more important, so if anyone can point me in the right direction to a fairly good source/ simple explanation of how much light in total particular orchids want, rather than the maximum fcs i.e 4000 for catts, this would help me in my placement of plants. (Sort of like a measure of light hours???)

For example, my catts and vandas are in my dining room window which is SE facing, and is now in direct sunlight. At 7.30am, the light levels read 1700-2000 lux, and now at 9am they read between 20-22,000 lux.

I have put net curtains back in, but those readings are for the window area behind double glazed windows but with no nets obscuring the light.

Again, I have read info that suggests if you plants are getting a couple of hours of direct sun, it may well be fine. I think there is too much sun on that window, but am having a bit of an argument with husband about whether I can put a table/ or small bookcase in front to put the plants on so that they are moved away from the light a bit.

This is turning into a long post, so I will stop. I will try and update this thread to show the differences in light levels at the different points if anyone is interested. The long standing members here may have all had the light discussion so many times that you are in fact bored of it, but I thought that seeing as there are a lot of newish members, me included, it might be helpful for us newbies to get a bit more info. (and of course I like talking, even in a typed manner to myself!). Especially at this time when there is no likelihood of me ever being able to put in supplemental lighting!

[Korxi]

I'm interested! Eventhough the words of the wise (not me) are that you should listen to the plants (not litteraly.. if you start doing that seek help), and adjust according to their needs.

What I'm most curious about is that measuring of amount of light over time.. Since I'm not getting very high fc measurements in my vivarium I was thinking that the constant "clear sky" in there might counterbalance this since there are no variations in the intensity ((guess I'm rambling now... better stop)

Christian

[Kerry]

That is what my main question is really. There is so much contradictory information out there. I have read that Catts require 4000 fc as a maximum at noon on a sunny day, but not what the minimum should be over the whole day, and then there are others that suggest they should have that level of light all day.

Am much confused!

I am happy to listen to my plants, but I guess with the catts I won't know until it's time for them to reflower whether or not they have had enough light.

I have been asking questions on a UK site too, as I thought there would be more people with my sort of conditions, but so far I have not had much joy. Hence my experiment.

Just after one sunny day, it looks like none of my windows (except my front rooms) are bright enough to sustain even low light orchids. But the readings for the front rooms went above 3400 fcs (the max for the light meter being able to read is about 33500 lux - after which you just get an error message).

We shall see....

[Korxi]

I'm from Denmark - so I guess my situation is more or less the same to - I never did measurements but I have had one catt. rebloom last fall in a window facing west (started collecting about a year ago).

[uncasteeb]

It is really difficult to give a concise answer to the total amount a particular orchid needs a day to bloom & flourish , there are just to many variables.
The amount of humidity & air flow can make a huge difference to the amount of light a plant can take and be happy.
With the high air flow in my growroom(humidity is usually 65%) my plants take a lot of foot candles over the lighting cycle , probably more than when they are in my green house on a normal day , but the growroom is the same every day.You would be surprised how much light a Phal can take with the right amount of airflow/humidity.
In my green house the shading gives a bout 55% to 60% shade , this means on the very bright days most of my plants get 4000 fc.I do use the larger plants to give the smaller less light tolerant some extra shade but they all seem to survive if a little frazzled .
I know where you are coming from looking for concise information , i have been there too , mostly it is just a try it & see situation.
Remember it is not the level of light that fries plants it is the heat build up in the leaves/PB's.
From my experiences & living in the UK your Catts & Vanda's should love a SE facing window , just make sure you have good air circulation & that you keep the Vanda's well misted.Keep an eye on the leaves for signs of distress , my few Catts often have red leaves when they first emerge but soon turn a nice green with a little red around the edges as the leaf matures a little.

[Kerry]

Thank you,

I have noticed a red tinge to the leaves, and I have been feeling the leaves to see how hot they are getting. But then again, I am too knew to know when warm becomes too warm.

I am sort of thinking "to hell with it, if they survive they survive" a bit gung ho I know- but i will probably learn more from actually making mistakes, as long as I keep an eye on them and make sure it doesn't go REALLY horribly wrong.

It doesn't hurt to keep asking those quesions though! The more opinions I get the more I can worry about, I mean, the more I can look for alternative solutions.

[Gin]

A red tinge usually means they are at or approching maximum light levels they can handle with out burn . It is like a sun tan .
Before the green house I had my Vandas in a east/south window sun until about noon from the south bright the rest of the time . They bloomed as well as in the green house one bloomed better in the house . Gin

[IdahoOrchid]

I have been told/read that the fc figure is for an 8 hour day. For example, if your plant wants 1000 fcs and you can only provide 500 then it needs to have that light for 16 hours and that would be the equivilant.

Fact or urban myth? Try it and see. Plants, by nature, are quite adaptable and have a built in need to survive. Since the only way they can survive is by flowering, I think that they can flower in quite a bit more variable conditions than we think.

[Becky15349]

I am interested in this conversation too, since I'm also new to the forum and grow my orchids on a widowsill. In the spring/summer months, I think my plants get around 4 hours of direct sun in the morning until around 11:30am; after that its just very bright indirect light. With my poor fiance not being too into orchids, there is NO way I could get supplemental lighting either...I'm just grateful that my window doesn't face north! haha

[Kerry]

A red tinge usually means they are at or approching maximum light levels they can handle with out burn . Gin

I am keeping an eye on the catts, as one of them is showing a distinct red tinge on a couple of the pseudobulbs. I have shaded it slightly with other plants, to try to cut the light slightly, but I know that it is going to get much brighter other the next few months in summer (when it's actually sunny) so I wanted to try to acclimatise it now to more sun, rather than suddenly forget to put the nets down one day in June and come home to find a crispy plant crisis!

I have been told/read that the fc figure is for an 8 hour day. For example, if your plant wants 1000 fcs and you can only provide 500 then it needs to have that light for 16 hours and that would be the equivilant.

Fact or urban myth?

I think the try and see approach is exactly what I am going to do. I have moved one non-spiking phal into the dining room to see if it respikes in this change of environment. However, this plant only finished flowering just before Christmas, and it's quite possible that it just wants a rest before it does anymore. But there are some rooms where the light just doesn't quite reach 1000 fcs all day, and is sometimes as low as 500 fcs. I know that I could move them about once they are done blooming, but it would be nice to see if a couple of them can make a permanent position for themselves.

I am interested in this conversation too, since I'm also new to the forum and grow my orchids on a widowsill. In the spring/summer months, I think my plants get around 4 hours of direct sun in the morning until around 11:30am; after that its just very bright indirect light. With my poor fiance not being too into orchids, there is NO way I could get supplemental lighting either...I'm just grateful that my window doesn't face north! haha

The sun shines directly into my dining room window from 9 am to about 2 pm. It still seems very bright and warm in here after that, but the light intensity drops hugely. In the rest of my rooms they don't really get the light until the afternoon. I need to think about the temperature in here as well, as when I am at work, I can hardly open the windows.

I have actually done a lot less measuring of light levels than I would like, as I have been gardening most of the weekend and kept forgetting to tramp in. I need to measure light in the afternoons, early evenings in the rear of the flat to see what the kitchen, bathroom and living room plants are getting.

Ditto to the supplemental lighting, but you never know, in time he might come round and a little plant trolley with lights etc might just pop into being! At the moment we have millions of books in our dining room. I am slowly selling them on eBay to make more room. I got fed up with donating them to the local library, as I must have spent thousands over the years on these books. So until the piles (and I do mean piles) have gone, there is no hope for me. He's also gotten it into his head that 1st and 2nd world war tank and artillery shells are really wonderful, so maybe if he starts getting more, then I can expand my interests too!