fluorescent lighting ???????????

chaznsc(7)August 6, 2005

I have a question about fluorescent lighting.

I have an old school desk that my dad refinished years ago and gave to me. Its a wonderful old piece of history. I have converted it to holding my african violets & orchids. My question is 2-pronged:

Do ordinary fluorescent lights provide a decent wavelength for plant growth or only the fluorescent "plant lights"? (the reason i ask is now i can buy fluorescent "screw in lights" for replacing in a standard lamp, i think.

Is there a tabletop fluorescent lamp I can purchase?

Do incandescent "plant lights" do any good? (it seems like i have read they dont)

thanks for any advice.


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compact flouros work very well. incandescents wont grow anything.

    Bookmark   August 6, 2005 at 10:53AM
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username_5(banned for no reason)

Do ordinary fluorescent lights provide a decent wavelength for plant growth or only the fluorescent "plant lights"? (the reason i ask is now i can buy fluorescent "screw in lights" for replacing in a standard lamp, i think.

Yes, they work fine and lights marketed as plant lights are simply overpriced lights.

When it comes to lights all you really need to be concerned with are lumens and color temperature. Lights are usually rated in watts, but this isn't a measure of the light output, rather the required input. Lumens are the measure of how much light is actually emitted. The higher the better.

Color temperature simply means what part of the light spectrum does the light emit. Incandescent lights are no good because the spectrum they emit is all wrong and they are very inefficient.

Unfortunately not all lights tell you their lumen output or color temperature.

Browse the lights at the hardware store and you will find something good.

The Sun's color temp is around 5000k. Go lower than that and you get a redish tint to the light. Go higher and you get a bluish tint. Some specialty plant lights emit only a blue and red and omit the rest of the spectrum. The result is a purplish looking light. I guess they work well, but haven't bothered with them myself. Other lights are 'natural sunlight' bulbs which are usually close to 5000k, like the sun.

It is believed that the more blue in the spectrum, the better it is for vegetative growth and the more red the better it is for flowering.

My though is that if you stick with a bulb that is in the 4500-6000k range you can't go wrong. If you want to get all technical and experimental go with lights outside this range later on, but for the basics stick with that range.

    Bookmark   August 13, 2005 at 2:56AM
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sdafamily(Z 6- tenn.)

i still need to have a straight answer...just tell me what bulb...exactly...to use?
i take so much meds. that i cant keep 2 thoughts together!
PLEASE just a simple answer....i wont fault your choice...i will run , or wheel right out and get it...
my plant stand is 4'long x 18" deep...room for up to 3 flourescent lights on each shelf, if needed??
i want to have a little of everything...seeds, cuttings,plants....
i have shop lights with 5000...makes plants shrivel up..
cuttings also drooped over...i am lost!
this is my first attempt, failing miserably!

    Bookmark   September 1, 2005 at 4:33PM
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risingpower1(Essex, UK)

Metal halides would be the usual setup for your scenario rather than fluoros I think.


    Bookmark   September 1, 2005 at 6:30PM
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dmarin(Z9 NorCal)

No MH for you.

What do you mean "shop lights with 5000"? Do you mean 5000K colored bulbs? If so, those will more than do.

If you are experiencing difficulties with seedlings and plants wilting under the lights, have you made sure you're not over watering? Do you have a fan blowing over them to cool them off and provide stimulation for them so they grow up nice and strong?

What are your conditions like(temp/humidity)? How close are the lights to the plants? How many hours of light are you giving them? I see you're growing orchids...what kind? Are you sure you're not under or over watering your plants and rotting/dessicating them?

    Bookmark   September 2, 2005 at 11:16PM
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Go to Lowes and ask for full spectrum fluorescent tubes. They cost about $6 each and work fine. I've been using them for 25 years to start seeds. Not hard at all.

It's the coating inside the tube that makes the difference. Those expensive plant gro-lites are coated with some expensive stuff. Plain full spectrum lights are sufficient.

    Bookmark   September 16, 2005 at 8:13AM
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klavier(Z7 Baltimore)

How high above the plants should the bulbs be? If I were to grow large amorphophallus plants, would I need a lot of fixtures? I am planning on using four foot long shop lights. to light a 4'X 8'area, would I need like four fixtured, two bulbs a piece? How is this method as compared to those big expensive bulbs with the hood that you see at university green houses, or in specialty stores? They certainly emit a hell of a lot more light than any florescent bulbs I have ever seen. If I were to grow like a thirty gallon fish-tanks worth of plants in another area, what king of screw in bulbs are best. Last year I tried screw ins, and the plants grew right into the lights, becoming very elongated and droopy. They all burned up as soon as they went outside in the spring even with the most gradual transitions I could make.

    Bookmark   September 25, 2005 at 7:40PM
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username_5(banned for no reason)


flouros are short range lights. The lights you mention in university greenhouses are HID lighting, either metal halide (MH) or high pressure sodium (HPS).

As a general rule the useful light output of a flouro at 6" is comparable (almost) to an HID light at 3'. What this means is that for large plants you won't get good results with flouros unless you arrange them vertically on multiple sides of the tall plant. This is a case where an HID light would be preferable.

Flouros are best for short plants, seed starting and things of this nature.

    Bookmark   September 25, 2005 at 9:59PM
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shrubs_n_bulbs(z8/9 UK)

flouros are short range lights

Wrong. Fluorescent lights are simply less bright than HID lights. A typical fluorescent tube is 40W and a typical metal halide bulb is 400W. The metal halide gives ten times as much light as one fluorescent tube, but ten fluorescent tubes have just as much light and "range" as a metal halide bulb. Read the link if you need more details, I'm getting fed up explaining this one so many times :)

For large plants, HID is more convenient, but you can use ten fluorescent tubes if you want. Make sure your fluorescents have good reflectors so they light the plants and not the whole room. For small plants, use fluorescent tubes and put them close to the plants. For a single tall plant, you might want to use several fluorescent tubes (instead of a more powerful HID lamp) vertically around the plant to save on your electricity bill.

Here is a link that might be useful: Ten myths, see #2

    Bookmark   September 26, 2005 at 7:43AM
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shrubs_n_bulbs(z8/9 UK)

I see I didn't answer part of the question. In a thirty gallon tank, use compact fluorescent bulbs because the tank is too small to mount long fluorescent tubes. Short fluorescent tubes are more expensive and not as efficient, you might not even be able to fit in enough to light the tank properly. Regular incadescent bulbs are no use, unless you feel like getting some 300W bulbs which will fry everything! Depending on the plants you will need between about 30W and 150W of compact fluorescents to light a thirty gallon tank. Again, make sure you mount them with a good reflector so that you are lighting the tank and not the ceiling :) Compact fluorescents are frequently available in "daylight" 6500K (maybe 5000K) and warm white 3000K colours, and sometimes in cool white 4100K. You can mix 6500K and 3000K successfully, or just go with 4100K or 6500K. Don't use just 3000K bulbs except for starting seeds. For growing under lights longterm or if you don't like the way the regular bulbs make your plants look washed out, then look for bulbs with a CRI of 90 or more, which might be called full spectrum. You'll probably only find these in the daylight 6500K colour. The regular spiral bulbs are fine, but also look out for straight tube bulbs, you can find ones that look like a fluorescent tube bent in half, maybe 12" long, they work very well for lighting a tank.

    Bookmark   September 26, 2005 at 7:55AM
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klavier(Z7 Baltimore)

Have any ideas of what are good things to make reflectors out of if all you have is just plain florescent fixtures?

    Bookmark   September 27, 2005 at 11:42PM
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The cheap route would be tin foil. You could also try aluminum flashing.

    Bookmark   October 26, 2013 at 7:50PM
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thornton_clark(8b GA)

I have to bring in 26 plants in large pots and dozens of small ones each fall. The room has two windows on the west side and one on the north. Admittedly, not great.

The room has 12 long standard flourescent tubes on the ceiling, which means they are about 8 feet above the tops of most of the plants. Is it doing any good to leave them on 24/7 or should just forget it and turn them off?

Thank you

    Bookmark   December 8, 2013 at 4:20PM
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