Effects of differing wavelengths of light on cana growth.

[Randalizer]

any way it has been documented by a fair few growers that, hps causes more stretch than mh, I think that's common knowledge.

Perhaps with blue light the plant stretches outwards more than upwards.

Again, it's strain specific methinks. I'm growing some Little Hands that are sativa dominant under a 400W MH and they are stretching like there is no tomorrow!

[NiKEUS]

any way it has been documented by a fair few growers that, hps causes more stretch than mh, I think that's common knowledge.

Perhaps with blue light the plant stretches outwards more than upwards.

Again, it's strain specific methinks. I'm growing some Little Hands that are sativa dominant under a 400W MH and they are stretching like there is no tomorrow!

are they stretchers anyway? would they not stretch more with hps..

[Randalizer]

are they stretchers anyway? would they not stretch more with hps..

Yes they are stretchers, hence my strain specific comment. But I see your point.

Would they stretch more under HPS? Don't know but when they go to 12/12 they'll be under HPS.

Edited October 19, 2010 by Randalizer

[NiKEUS]

are they stretchers anyway? would they not stretch more with hps..

Yes they are stretchers, hence my strain specific comment. But I see your point.

Would they stretch more under HPS? Don't know but when they go to 12/12 they'll be under HPS.

i thought hps = more stretchy plants but better yield from flower, mh stockier plants with tight node spacing, less yield from flower.

i cant say either way from experience as i use cmh bulbs through veg and cmh + hps through flower and as a plant it has a stretch phase anyway i cannot judge on past experience, on one way or the other but from reading other peoples diary's and experience i came to the conclusion cmh + hps was the best bet (with a lil bit of extra uvb in the mix )

[Super GG]

great post and info Randalizer

i made a thread about something related. light spectrum of pl-l fluorescents and was hoping you would take a look

i explained i found pll fluorescent light that exactly hits 450nm

im starting to think think this could replace the current cfl veg rooms, metal halides and used with hps side lighting to keep streching down.

wa u think

[teacup]

I am very much interested on this topic specially giving blue in the last one-two weeks parts. I read almost all the posts but all were about MH, HPS. Will it give similar effect with CFL lights as well? I mean will be the same if i start flowering with %70blue %30red then switch to vice versa for last two weeks. Of course there will be air buds with CLFs but can this make them more compact or this is just useless for CFLs?

[wildbill]

Nice thread Randalizer, I will read it in it's entirety when I have more patience

I just wanted to say that 10 years ago (before digi ballasts were common), when Sensi Seeds sold grow kit they gave the following grow advice about lamps:

If you only buy one lamp buy a MH, if you buy many lamps -the ideal mix for flowering is 2 MH for every HPS.

Now I dont claim to have anywhere near as much exp as growers like OT1, but I have never had any reason to doubt this advice. I have personally never used just HPS for flowering without adding some blue light.

The way I think of it is that using just HPS for flowering is like forcing, it produces more flowers quicker. But my interest is focused on quality & health rather than yield.

[jailbait]

Nice thread and one day i'l read it all but hear are my thoughts on why plants namely mj stretches under hps. In autumn and winter the sun is lower in the sky so more red spectrum light will reach the plant as blue does not travel so well so by growing under a red light the plant is thinking its winter time and its energy is better spent growing tall so it stands a chance of catching pollen whiles under a blue light its thinking hey its summer time plenty of time left to grow tall enough to catch pollen.

[Randalizer]

Howdy folks.

Sorry to not have dropped in for such a long time. I just wanted to reiterate a few things:

I started this topic, not because I know so much about lighting for cannabis, but just the opposite. I know/knew very little and was hoping to have a bit of a forum where we could all share our experiences in the hopes of us all learning. So for those that keep asking me advanced questions, sorry, but I'm not an expert.

2nd, I still believe the growth characteristics of a plant are largely determined by genetics. You can give a plant the best environment possible (which actually would be outdoors), but a plant can't do beyond what it is programmed to do. Or so it seems.

I'm still not a fantastic grower. I'm getting there but it is a slow process. After a few more grows and having the kind of results I am looking for, I will probably be in a good position to do some trial runs. At that point I'll try different things, including different lighting regimes.

Based on what I have learned so far though, imo a sat dom hybrid should be vegged with a MH (unless you want really fast growth and don't care about internodes) and a indica dom hybrid should be vegged with a HPS (since they are such stocky plants anyway). Your results may vary.

As far as flowering goes HPS seems the way to go. I am of the opinion that pretty much everything else should be sorted before playing with lights, although if your ballast can handle both MH and HPS, it should be very easy to swap out lamps at the last two weeks of flowering.

Personally I think if one is going down that road, some UVB light (from reptile lights) would be very helpful during this time, but reptile lights need to be handled with caution as they can cause eye and skin damage. Research well the dangers before using and a UVB meter would be the ideal way to see what you are actually giving your plants.

Comments and corrections are always welcome.

Edited July 15, 2011 by Randalizer

[NattyFido2]

Not sure how I missed this thread man. Looks quite enlightening. Pun intended.

I have a quick question though before I read more. I just read that green light has no effect on the plant and that the plant is blind to this spectrum. Yet it said that a plant grown solely in green light will be weak and small. If this is the case, surely it does use that light. Otherwise how would it grow at all, even if it's growth is weak. To me this means that the plant must use green light if it responds to it in any way. Or am I missing something? I'm not saying it's any good for growing with. I'm just wondering if it's true that green light has no effect.

i think the green light thing is similar to the way outdoor plants don't hermie even when theres street lights and the moon. intensity i reckon a plant receiving the suns strong rays isn't affected by the weak light levels given by a street lamp down the road. plants arent using a lot of green light so its not strong enough to give any bad effects but just like the street lamp over there it may be enough to sustain a plant if its all the plant has ever seen (nothing more intense)

all imo

I reckon the reason plants don't respond to green light is because the leaves are green! What I mean is, green objects reflect green light and absorb the other colours. Likewise, if an object is red, that means it is reflecting red light and absorbing the other colours.

Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light. Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion. However, it is a poor absorber of green and near-green portions of the spectrum; hence the green color of chlorophyll-containing tissues.

[Randalizer]

I want to thank SaddamHusain for posting this video in another topic.

[Fungai]

What im wondering is if u had the means to use both a MH and HPS at the same time during flowering would that be better than changing between the two at different stages of flowering (and would using both during the the whole life of the plant [veg and flower] be detrimental to the plant at all?). Does anyone have any experience of this, if so if using them separately which light should be used at which stage of the flowering process?

Also im probably asking for a bit much here but at which stage should uv be introduced into a grow room to aid resin production?

cheers

[Guest Thicky]

There is information somewhere on a thread in here which oldtimer posted results of an experiment he did using MH in the last two weeks but can't find it anywhere at present. Will keep looking (unless someone pops in and leaves the link)

[Fungai]

There is information somewhere on a thread in here which oldtimer posted results of an experiment he did using MH in the last two weeks but can't find it anywhere at present. Will keep looking (unless someone pops in and leaves the link)

Im new to all of this but Oldtimer1 seems to be a very respected authority around here. From what iv read i can see why he really does seem to know his stuff and has a good philosophy about things (I would love to run my set up and set up ideas past him and get his opinion). im trying to read what i can of his advice so ill keep my eye out for that post if i do find it ill post it up.

[silverhazey]

Brilliant thread!

Arnold Layne also seems to use MH for last 2-3 weeks of flowering so think I'll adopt this method too - HPS for main grow and initial flowering then switch to MH for last few weeks. Think I'll also try and use a UVB towards the end of cycle too as this seems to increase potency.

Cheers all for great info!