How long to light my propagator

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simon
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Re: How long to light my propagator

Post by simon » Wed Feb 13, 2008 2:59 pm

I'm a bit confused. I'm not familiar with the market for lighting specifically for plants, as I haven't got into this side of it yet.

John Jearrard said that you need incandescent lighting beacause flourescents don't give the red end of the spectrum required "to influence the particular photochemical 'switch' involved". I know that during photosynthesis plants absorb light across the entire spectrum (except green) but I presume John is saying they need red to trigger the process.

If this is so, as these companies sell flourescent lights for the purpose of growing plants, are they selling something that doesn't work or can they make flourescents that do produce light in the red end of the spectrum?


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Dave Brown
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Re: How long to light my propagator

Post by Dave Brown » Wed Feb 13, 2008 7:41 pm

I have heard that Sodium lights are used to promote flowering in Dutch greenhouses. This seems to be a whole science of its own. In the same way as NPK is tweaked to get the desired results, you have to tweak the red /blue end of light promote the same. Does this mean the right fertilizer but the wrong light counteract each other, :roll:
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helen
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Re: How long to light my propagator

Post by helen » Wed Feb 13, 2008 8:14 pm

Andy I use 125W envirolites. 3 of them :)
Be careful, it's a jungle out there!


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Re: How long to light my propagator

Post by Andy J » Wed Feb 13, 2008 9:01 pm

The thing with flourescent tubes whether compact or the usual straight type is the the coating of the tube can be tweaked to give a different colour temperature depending on the use. Just go into a fish shop and see the number of different tubes available. Then just to further cloud the issue i run a 10% uv lamp for my tortoise and there are several different types of those too! (lamps and tortoises!)
Personally i think that enviorlites are a good cheapish solution to lighting plants.

Helen,your 3 beats my 1,you win.........this time! :lol:


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simon
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Re: How long to light my propagator

Post by simon » Thu Feb 14, 2008 1:09 pm

Just as a useful comparison:

100 Watts of incandescent light concentrated into 1 square meter gives a light intensity of approximately 1,700 lux.

100 Watts of Sodium vapour light concentrated into 1 square meter gives a light intensity of approximately 15,000 lux.

Daylight gives a light intensity of between 32,000 and 100,000 lux.

Bear in mind that unless you completely enclose your lamp and the sides of your 1 square meter of seedlings etc. in reflective material, a large proprtion of the light intensity from an artificial source will be lost.


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Re: How long to light my propagator

Post by Dave Brown » Thu Feb 14, 2008 1:23 pm

Would a photographic light meter be useful for measuring the artificial light intensity? It is difficult for the human eye to determine as your iris compensates.
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simon
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Re: How long to light my propagator

Post by simon » Thu Feb 14, 2008 1:27 pm

Absolutely Dave, are they expensive?


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Re: How long to light my propagator

Post by Dave Brown » Thu Feb 14, 2008 1:51 pm

Just had a quick look and it seems they are a wide range of prices. Just found this Moisture and Light meter. £13.99 at the moment. 8)
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Re: How long to light my propagator

Post by Andy J » Thu Feb 14, 2008 3:28 pm

And just to further confuse the issue(as if we havent already!) the further away from the light source the lower the lux. My envirolite is as close to my plants as possible,approx 6" above and this is where a flourescent tube has the advantage over an incandescant bulb as most of its power is turned into light whereas an incandescant bulb produces mostly heat and would toast the plants at that distance.


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Re: How long to light my propagator

Post by Andy J » Thu Feb 14, 2008 3:52 pm

Had a look on ebay for LUX meter rather than a light meter and found quite a few and the prices arent too bad. Im may well be getting one as i am now curious as to how much light ,well lux really my envirolite is putting out compared to a sunny windowsill or just outside.


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simon
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Re: How long to light my propagator

Post by simon » Thu Feb 14, 2008 4:11 pm

Looks like it may become another 'must have' gadget for the exotic gardener :D .
Andy J wrote:And just to further confuse the issue(as if we havent already!) the further away from the light source the lower the lux.
This is because the further the source is away from the target the more light is lost elsewhere as the solid angle of target the becomes smaller. If you concentrated the light using reflective surfaces the light level would be the same regardless of distance.


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