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Cheyenne, Wyoming

I have heard several times about the positive effect on the growing plant, of both red and blue light in the hot house.

Which color is better?

Would it be beneficial to run two lights, one red and one blue?

4/3/2005 1:06:28 PM

Phoenix, AZ

There has been much study on this subject. Basically for vegetative growth, you want blue light and for flowering, you want red. That is the short basic answer.

Although technical, this link will help explain thing.

http://www2.mcdaniel.edu/Biology/botf99/photo/p3igments.html

4/3/2005 2:41:26 PM

Appalachian Mtns.

I used blue last year on one plant and it helped growth...nice dark grren cots and leafs until transplant.

4/3/2005 8:33:37 PM

Ljubljana, Slovenia

One point is crucial: plants sense far red (FR, it is abundant in usual light ball) as being in the dark. The reason for this is that only FR does not get filtered by the leaves in the canopy, so the plants use it as a signal to invest all their energy to grow taller - to outgrow the canopy above. The result are thin&tall plants, which we do not like. Short red works the opposite way as FR and similarly as blue/UV, which however act by other mechanisms.
Btw, plants sense reflected FR from a nearby plant and thus sense its vicinity although they are even not in their shade… FR stimulates growth of the stem on the FR illuminated side so the plant grows away from the neighboring plant. Yes, we might say that plants can see…

4/4/2005 5:51:01 AM

[email protected]

Well done Jernej. This is why red light is used to illicit flowering in photoperiod sensitive plants. No good is likely to come from treating AGs this way. I would thus recommend using full spectrum lights of the "bluer" white light sort.

4/4/2005 11:33:41 PM

Thornhill, Ontario, Canada

What about "black" lights? I think that they are really more purple than anything else. So, would they contain the best of both worlds, some blue, some red?

4/5/2005 1:48:13 AM

Ljubljana, Slovenia

crammed, what do you mean by "black" light?

4/6/2005 4:35:00 AM

Oz

I use a hp sodium light to start seeds.
In the center of the "beam",seeds always pop out first.

4/6/2005 7:52:26 AM

C N Y

all right! psychedelic pumpkin-growing!
i dunno how to explain it, Jernej, but a blacklight produces
light of such a wavelength that it causes ordinarily-colored
objects to flouresce, like glow-in-the-dark, compared to other objects....ever been in a nightclub and your white shirt or shoelaces are bright as heck and everything else
is kinda dim? a blacklight is probably responsible.
now, back to "how is it gonna grow us a 1600#???"

4/6/2005 6:25:58 PM

Ljubljana, Slovenia

Black light is then “short” blue – violet or close to UV (similar as in sodium lamp). This short wavelength light has high energy so after hitting pigments in white shirt cause them to fluorescence – emit light of longer wavelengths (lower energy)… I seem to be complicating on everything.

Psychedelic.. maybe, but I am dead serious about the plants that can see :-) .. watch out next time in the woods!

4/7/2005 3:11:50 AM

Ljubljana, Slovenia

I have to correct myself: first, I have confused sodium with mercury lamp (although there might be combinations of both). Secondly, under the canopy besides FR also green does not get filtered by leaves.. thats why the shade under trees is called "green shade".

4/7/2005 4:26:55 AM