Growing Orchids Under Lights - Discussion

[mayres]

I have found the following link to have an EXCELLENT portion on indoor lighting of orchids - http://www.orchidsusa.com/3Lightlevels.htm.
For starters, I found the measured light intensity in September, at noon, from a large south window interesting -
6000 fc by the window
4000 fc against the screened pane
3000 fc 1 foot away (in sunlight)
600 fc 2 feet away (in shade)
500 fc 3 feet away (in shade)
400 fc 4 feet away (in shade)
<200 fc 10 feet away under a skylight!
Note especially his comments about growing under fluorescent and high intensity lamps!

I also have a fairly good book by Charles Marden Fitch termed "Growing Orchids Under Lights" which promotes either HID lighting or special horticultural fluorescent fixtures that hold EIGHT tubes in about a 16" width. Even with this many bulbs crammed into a small space the plants are just inches from the fixture (which is not necessary with HID lighting that has its own challenges).

What I "THINK" I have learned from all this is that only my phals and paphs will do well with my shop light fluorescent setup and my other medium and high light need orchids need to be outside as much as possible to promote blooming during the nice weather portion of the season. After a year and a half this is indeed what seems to be the case.

Anyway - possibly this will promote some more discussion and you all can help me gain additional understanding about how all this works! mike

[arleneg]

In reply to Mike's question from this post in the Growing Spaces thread...

I use a light meter. Top shelf lighting has two 3300 lumens regular fluorescent lights + 2800 lumens of the Natural Sunshine lights. Bottom shelf lighting has two 3300 lumens + two 1600 Plant & Aquarium lights. Each light is 40 watts.

Could it be that my metallic light fixtures are helping increase the light levels? Maybe.

Tomorrow, when the lights are on, I'll try using my digital camera to measure the light intensity and post my results when I get a chance.

[DDS2007]

a newbie question , again !

can u plz list the names of low light , medium light , and high light orchids ??

thank u sooo much

[cutterpup]

I don't have pics to post yet, but here is a deiescription of my indoor area. I have a four foot by three foot shelf under a western window. The window is shaded by a twentyfoot wide porch so it gets light but no sun. Ihave two fourfoot shoplights, each having a "warm" bulb and a "cool" bulb in them plus a clamp on light with a cfl "daylight" bulb amimed directly at the minicatts.
I use wire shelving to adjust how close the plants are to the lights. During the summer I move all but paphs outside to the porch and start bringing them in as the nights get colder. The phals come in first, then the oncs, then the catts with the zygo staying outside until very late in the year.
Once back inside I have a series of blooms going most of the fall, winter and spring.
Hope this helps
Judy

[mayres]

Arlene - what kind of light meter are you using? Is this a $20 unit or $100 unit? Just wondering about accuracy? Will be interested to see what your camera says! You are using the same type tubes I am. When I put my sensor right up against the center of the tube with NO reflection I get 1000 footcandles.
DDS - light levels of plants will vary a little depending upon who you ask, but I've noted the following separation used by some.
Judy - looks like we are working on much the same principle of putting plants out for the nice weather and then moving in for the winter. I've noticed the same positive results as you. I have not put my paphs and phals outside yet though as they continue to do wonderfully under my lights indoors - not sure I'd get any advantage by moving them - other than I could turn off my lights for awhile.
mike
1000-1500 fc - low light orchids
1500-3000 fc - medium light orchids
3000-4500 fc - high light orchids

[Fabolusus]

One thing that article doesn't take into account is the use of light movers, especially with HID lights. They can greatly increase the usable light and also allow you to place your orchids a lot closer to the light source.

[mayres]

You are correct Fabolusus - the book I noted goes into that extensively - Charles Marden Fitch's "Growing Orchids Under Lights".
Here is another article on lighting that has some good information - http://www.simplyhydro.com/why_hydro.htm. It also mentions light movers with HID lighting for efficiency.
Arlene - notice the part on fluorescents - partly copied here -
"These tubes produce 68 lumens per watt, for a total of 2750 lumens. Fluorescents are ideal for initial propagation because they produce almost no reciprocal heat. You can hang a four tube fixture six to eight inches above your plant canopy, and then just keep raising it as your plants grow, without fear of burning your leaves. In this example, we will scale down the size of our test garden. Earlier, we have been using a five feet by five feet garden as a reference point. For this example, we wil use a two feet by four feet garden. A two feet by four feet fixture can hold four bulbs. This will give us a total of 11,000 lumens (4 bulbs multiplied by 2750 individual lumens = 11,000 lumens). Allowing for "spilled" light, we are probably generating about 1031.25 F.C. (11,000 lumens multiplied by 75% = 8250 lumens...8250 lumens divided by eight square feet = 1031.25 Foot Candles). This is assuming that the lights are placed DIRECTLY over your plants. As you raise your lighting, your light intensity drastically drops. When you double the distance between your light and your plants, you cut the light intensity by four times."

[arleneg]

First, here's info on how to measure light intensity with a 35mm camera (according to the link Mike provided in his first post on this thread):

You can also use a 35 mm camera to measure light. Here is how to do it:
• Set the camera at 25 ASA.
• Set the shutter speed at 1/60 of a second.
• Place a white sheet of paper where the leaves of the plants would be.
• Focus on the white sheet of paper from a distance of 1 foot.
• Make a note of the f/stop shown in the viewfinder.

Here are the approximate foot candles corresponding to various f/stops:
f/2 = 100 fc
f/2.8 = 200 fc
f/4 = 375 fc
f/5.6 = 750 fc
f/8 = 1,500 fc
f/11 = 2,800 fc
f/16 = 5,000 fc.

Remember the maximum light should be at noon on a bright summer day.

Using the following settings on my SLR camera (equivalent to a 35mm film camera),

100 ISO (the lowest on my SLR digital camera)
1/60 of a second shutter speed

here are my results from measuring the fluorescents lights in my shelf unit.

Bottom shelf
• Humidity tray surface (2 1/2" from shelf surface) = f/6.3 - 7.1
• 14" from fluorescent light surface = f/9 - 10
• 1" to 3" from light surface = f/16-18

Top shelf
• Humidity tray surface (2 1/2" from shelf surface) = f/8 - 9
• 14" from fluorescent light surface = f/10 - 11
• 1" to 3" from light surface = f/18 - 20

[mayres]

Arlene - "If" I understand this correctly - since you used ISO 100 instead of ASA 25 (note ASA = ISO American Standards Association vs. International Standards Organization), that means that your values should be FOUR TIMES the values given in the example listed before your values. A value of 4000 with your camera set as you listed it is actually only 1000. Anyone - chime in and correct me if I'm not seeing this correctly. If this be correct, we are now coming into some realm of commonality in values.

Here is another link on plant lighting that I have found particularly interesting and useful. http://retirees.uwaterloo.ca/~jerry/orchids/light.html

[mayres]

More Info - Here are light intensities in footcandles noted from the University of Missouri Extension Service for fluorescent 40 watt tubes - depending upon lumen output of individual bulbs - your results may vary slightly - but will give you the general concept/intensity to expect:

2 tube 2 tube 4 tube
unshielded shielded shielded
1/2ft 500 700 900
1 ft 260 400 600
2 ft 110 180 330
3 ft 60 100
4 ft 40 60 100

[kmarch]

For quite some time i successfully grew and bloomed quite a number of Paphs, Phrags, Coelogyne, and other smaller-sized plants under 2 florescent tubes at a distance ranging from 6-12 inches. According to Maryes' Missouri numbers mentioned above, I should not have been able to bloom anything at all. This would seem to be a case where the numbers and what happens in practice (for one reason or another) simply don't line up.

For this reason I put very little stock in numbers for blooming orchids and find light descriptors (bright indirect light, partial shade, dappled sunlight, etc., etc.) to be much more practical. Even here in Australia I grow and bloom Cattleyas in a south window (equivelant to a Northern Hemisphere's north window) where they receive no direct sunlight at all. Buy the numbers on a light meter, I shouldn't be able to do this. I also find that many hobby growers given a choice of spending $100 on a light meter or $100 on plants would choose the plants 99% of the time. The numbers mean nothing to most.

Now I realize that we're talking about growing under lights in this thread and that means trying to approximate the effects of sunlight with something artificial, but even in these cases (for example 3 friends of mine who grow in their basements under lights) I find that people still frequently do not use light meters and instead try to compare their artificial light conditions to natural light.

[mayres]

kmarch - were your plants in a basement type setting with NO other light, or were your fluorescents providing supplemental light? Many people use their artificial light as supplemental - which is another game altogether. Length of time per day is probably another factor that has not been discussed on this forum much. How much can the additive value of light over time in a day be used to make up for the lack in intensity and how much darkness is necessary for the plants to thrive?
The bottom line is definately WHAT WORKS. Wherever/however each person can get these beauties to bloom and flourish is what we're all after - good point. On the other hand, no one wants to "waste" a season or two experimenting to find that their plants are not blooming in a condition if they can immediately move to a condition that works. At least in my environment (for example) I've talked to people who wonder why their plants are not blooming in a north window or why their dends are not blooming a foot away from two fluorescent tubes. Not always, but in very general terms, if the plants look healthy but are not blooming - MORE LIGHT. At least that is what I "think" I have learned?
I'll take the plants over buying a meter too! Fortunately I have one at my disposal where I work that I can borrow. Also, as has been noted many times, many cameras have the ability to give one a good approximation.

Thanks for the comments - differing points of view make these threads very interesting......

[kmarch]

mayres, My light stands were not in a windowless basement but neither was it in a window, so no direct light and I'd say only a little indirect light. I would say the florescent light was the primary source with the natural light being supplimental. I did use timers to carefully control the number of hours of light, 14 hrs in winter, up to 16 in summer so maybe what you suggested, happened. Maybe what I lost in intensity, I made up for in length of "daylight."

The addage "you learn somethign new every day" applies here. Even after 10+ years of growing, I did not know, nor had I ever heard, the intensity/length-of-day question you posed. It never occured to me you might compensate for an intensity deficit by lengthening the "day."

It's quite interesting.....

[butt0n]

What does 1820 lumens translate into fc? I'm still trying to educate myself better on the whole light measuring issue.

[mayres]

Lumens are usually used to rate the amount of light production a lamp is capable of producing - keep in mind that this disintegrates with time/age and as the lamp becomes dirty. Footcandles have to do with the intensity of the light striking the measuring source (such as your plant's leaves) at any given point. To maximize utilization of lumens you want to direct as high of a percentage of the output as possible at your plant(s) - this is done by keeping them close and by directing as much as the light output as possible towards the plant through shielding/fixtures.

[Julie_M]

Let me chime in here and add that it is not necessarily the amount of light received at any one time during the day that makes the difference but rather the TOTAL amount of light received by the plant. For example, let's say that I have my Oncidium outside where it receives 3 000 fc for 8 hours. That's a total of 24 000 fc. Inside, under a 4 tube fluorescent light, it receives 1 500 fc during 16 hours. That's also 24 000 fc. This is usually why lights are on longer than the actual daylength. Let's also remember that the advantage of artificial lights, fluorescent or HID, is that the light intensity is stable over the entire day, whereas natural light will fluctuate naturally, when clouds go by for example, reducing that total 24 000 fc.

Julie

[mayres]

Julie - thanks for the comments - the additive properties of light over time is something I alluded to above. Any idea how much you can carry that principle to the exclusion of darkness? On the opposite end of the spectrum - how much darkness do they need?

[Julie_M]

Mayres, I don't know whether there is an actual minimum night required. I even remember a post, somewhere that totally escapes me at the moment, about someone who had his lights on for 24 hours a day for months at a time and did not report any adverse effects on his orchids. I've never tried this and don't think that I will (all that brightness at night + even higher energy bill = not for me).

The shortest "night" I've ever seen referenced anywhere for orchid culture under lights was 6 hours, with an 18-hour day, at the height of summer. What has been consistent across the web and book references I've read, though, is that there has to be some kind of gradual seasonal change - longer days in summer, shorter days in winter.