Re: [CH] What R these ? (abt lights)

Nikos Kalofolias (
Sun, 19 Apr 1998 13:38:17 -0700

Schoenbacher, Anton wrote:
>      One last question, I'm considering starting to use some type of
>      high pressure grow light (I'm sick of setting up a bunch of
>      flourescents).  Does anyone know if you need to keep plants close
>      to those things ?  Like they say keep your plants no less than 2"
>      from your lights or they get spindley, does this apply to big
>      lights ?
>      --Anton--

Well Anton I guess your talking about metal halides.
I 'll tell you the few things I know. (they are really few :)

Get metal halides and not hps(high pressure sodium).
MH are blueish and best for vegetative growth while hps are redish
best for flowering stage. I suppose you need the former.

Also hps are to be used only as supplementary lighting to sun or 
metal halides.

Hps are more expensive and produce more lumens/watt

I think mh burn more easily and you have to replace them often even
if they are still ok since light output drops after a while , though
if you only use them to raise seedlings to garden transplants they
should last for a long time I guess.

There are some Mh called something like daylights and also the Philips
son agro that have even more red spectrum so they are a more complete

If you buy a mh system you can't use a hps lamp and vice versa although
there are conversion lamps (not cheap) both ways.

You better save a few bucks more and buy a 1000W(8'x8') or at least a 
400W(5'x5') system , since a 250W covers only an area of (3'x3') when
used as the only light source.

The problem with these lamps is the tremendous heat they produce. So
you better keep them away from seedlings or you get chipotles ;)

I *think* 2'(feet!)for a 400W and 4' for a 1000W should provide adequate
light without any danger but you better ask around. My advice is don't
listen to anyone and find out for yourself by experimenting( start high
and if they become leggy then lower etc). Don't forget that anywayz you
will have to raise every so often since your seedlings will grow bigger
unless you are like me and can't grow weeds in a greenhouse ;)

That's more or less all I know about it. Use it at your own risk.
I haven't ever used mh/hps and in fact I would appreciate your posting
any results good or bad since I'm also interested in buying them next
year maybe.

Take care

PS: Don't buy halogens , they produce even more heat for less lumens.