"Jeff Layman" wrote in message ...
On 01/02/2011 00:58, p.mc wrote:
"Jeff Layman" wrote in message ...
(snip)
I think that you will find that you will find the light level from
standard strip fluorescent lamps is inadequate once the plants are out
of the seedling stage (ie more than 3 or 4 cm high). Not only that, but
although it may not seem apparent, these lamps produce heat as well as
light, and in close proximity to the plants that will have an effect.
Standard fluorescent lights produce 50 - 100 lumens per watt. If you
look at the link Chris Hogg gave, and get details on the Grolux lamps,
you'll see that these 400w lamps are rated at 58000 lumens (ie around
150 lumens per watt). They also produce a fair amount of heat, but as
they are usually at least a metre above the plants, that is not so much
of a problem.
I think you will find that it is not cost-effective for the amateur to
use artificial lighting to raise seedlings. If it was, we'd all have
been doing it for years.
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original poster
Hi Jeff
I suppose it should be called supplementary lighting when in a
greenhouse (not dark basement/garage). Although I now have them on for
16hrs a day, the seedlings also receive the natural light available for
this time of year in my cool greenhouse (11 degrees C at night.) And
the artificial light provides a few more hours of light at this time of
year (1st Feb). I suppose it's about trying to emulate the weather
conditions a couple of months ahead of time where the days are longer
and the nights warmer.
I'm not growing orchids or tropical plants so I don't see the need for
the overpriced cannabis jobs. The T5 tubes give off very little heat at
all and can be almost on top of the seedlings without a problem, at
least mine are ok, and I'm sure if they were too hot they would have
perished by now.
I've read quite a bit on this now and the general advice from pro's &
amateurs' is 40W tubes (T5s are better, but T8s suffice if not growing
tropical), 16hrs a day close to seedlings.
One question though. Are you saying I should remove the 3/4cm seedlings
from under the lights at that stage; or carry on giving the
supplementary light; does that mean at that height they will still grow at
the same rate without it?
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Reply
Firstly, as you are using Windows Live Mail V15 I have had to paste copy
and paste your reply as WLM does not deal correctly with previous
replies (your post appears as though it is a continuation of my
signature! My newsreader - and all others - strip signatures from
replies, so everything you have written in reply to my post gets lost
when I reply). I have therefore quoted your reply above between the
++++ lines.
As to whether or not you remove the seedlings, well, you can always do a
trial if you have enough seedlings - just put half under the lights and
half outside in natural light and see what the difference is!
Seedlings with only their cotyledons (first leaves) will not need
intense light. These "seed" leaves are really there to get the seedling
going after it has germinated. It is the true leaves which are the
factory driving the plant's growth. These will respond to good light.
The problem is that fluorescent lights will work for a few cm, but
after this the light level dies away quickly. So as the plants grow,
and you have to move the lights up to accommodate the growth, the top
leaves will get the intense light, but the lower ones won't.
If you want to look at the science behind these light levels, see
http://en.wikipedia.org/wiki/Lux. The bottom of the table in the
Explanation section and the second paragraph in the next section (Lux vs
Lumen) show the difference between sunlight and fluorescent light.
Please let us know how you get on if you do have enough seedlings to
split between supplementary lighting and just daylight.
--
Jeff
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Original poster reply
Hi Jeff
Sorry about the reply palaver. I noticed that myself with this mail prog
(WLMail). I use OE6 on my main machine, but I'm posting on my Win7 lappy,
which requires you to use a different mail prog other than OE.
Anyhow thanks for the reply. I had read all the science before, but on
further reading as I said some armatures & pro's were stating my above
method as how to do it! It is a bit of a of a contradiction, but I suppose
you go with what's more affordable. To be honest, if someone said.."Don't
bother they'll grow exactly the same without the lights even at this time of
year" (1st Feb) I would be a happy bunny. But is that the case or not?
My Polytunnel has a mesh woven into it which partially restricts the natural
light available, and also you can't depend on nice long sunny days until my
last frost date. I suppose an answer to "is this the case or not" would help
a lot.
Regards
p.mc
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