What light is best for lettuce?

[serial_killer]

I just got myself a new 600 watt HPS/MH for Christmas so I am going to take the 125 watt CLF I have been using and move it to my lettuce. Up to this point I have had them under a 30watt T8 with one red and one blue bulb but thats leaving a lot to be desired in growth and causing some streaching too.
What spectrum is best to use? I have both a 2700K bulb and a 6400K bulb what one should I use or should I start with one and switch to the other as some point?

thx

[jal_ut]

Those are some serious lights. What are you going to do heat the house with them? That will make the meter turn. You best unplug the lights and go buy some lettuce. It will be cheaper.

What most of us use for grow lights are just regular garage flourescent four foot long fixtures with two 40 watt tubes in them. They are hung on chains over the plants and adjusted to be 4 inches above the plants. I use daylight type tubes, but don't think it matters too much. Two of these fixtures will cover quite a few plants and it won't break the bank to leave them on 24/7.

[tomf]

The 6400K is about the day light us it.

[rainbowgardener]

Agree with every word jal_ut said, except I only leave my lights on 16 hrs a day... My seedlings tend to start getting a bit leggy if they don't have some rest periods.

[MysticGardener67]

Ue the cool white for your lettuce. 6400K stimulates leaf growth. 2700K stimulates flowering and fruit production. The stretching is most probably due to not enough light reaching the plants. That is the only bugabear of florescents is that they are not terribly intense compared to the halogen units.

Lower your lighting units will fix that problem. no more than 3-4 inches above your crop. I like to suspend my mine from small pullies. makes it really easy to adjust.

[serial_killer]

Thanks everyone, I forgot about this thread for a while and was going to come back in and edit it cause I answered my own question but you guys did it already.

Mystic you hit the nail on the head, I should have figured a vegetable needs light suited twards vegetative growth. BTW if your wondering why I run a High Pressure Sodium and not a metal halide its cause HPS give off more light per watt that MH, even though its the wrong color its not like its bad for them, and to me more light over rides prefered color.

And actually Jal, I do use the exhaust from my HPS for heating the garage. I pull in outside air, run it threw the cool tube then dump it into my attached garage. The 125W CFL doesnt get hot though, you cant leave your hand on it but you can touch it no problem.

Its only $25 extra a month to run my lights/ventilation. As for buying lettuce, that wouldnt do to much for personal gratification would it? I'm not paying for electricity, I'm paying for happiness / enjoyment of my hobby, in fact my other hobby (muscle cars) is a whole lot more expensive and doesnt provide me with food in the end.

I'm running my lights 16/8

[MysticGardener67]

had me wondering, do leaf crops, such as lettuce, really need a night cycle? I suppose I could do my thing and go digging through the interwebs, but honestly, I am being lazy tonight.

[serial_killer]

Absolutely. Dark period is important, since the canopy cant grow without light, and the roots doesnt need light it gets to put all its energy into root production.

I have even heard some people say that any light during dark period can cause problems, even as little as ambient street lighting for outdoor gardens. I have never noticed that though, previous indoor crops of lettuce did fine with a little indirect light during dark time, this current aeroponic crop is the same way, light ambient lighting during dark time.

Now for my garden room with my HPS no light gets in at dark time and if I need to go into the room I use a green flashlight, since plants don't see green light. I am growing 16 peppers in single plant DWC buckets, tons of carrots in a flood and drain table(EBB&Flow style) and a banana tree in a waterfarm. They are thriving, well the banana tree I just got yesterday but the other plants are great! Only reason the lettuce isnt in there is cause it never did well with higher temps, its 84 in the room, with that much direct lighting and the heat they wilt in the aerochamber unless I run the pump constant, and then the water gets warm... Its an endless cycle of temperature nightmare. don't forget the even more important water temps I have to control in hydro/aero <70* at all times OR ELSE.

[MysticGardener67]

See, what had me wondering is I once saw a program on television about gardening in Alaska.

They showed these GINORMOUS cabbages.. I would say between 24-30 inches across! The narrator said it was due the long arctic days.

I think that I may do extra research on this in the next few weeks.
I'll post once I get it all figgured out.

[rainbowgardener]

Let us know what you find. Everything I have seen recommends 6-8 hrs of darkness for lettuce, but it's hard to find anything that says why or what would happen if you grew it in constant light.

My personal experience is as noted above. I start lots of seedlings under lights every winter. I have experimented (informally, not with good controls or records) with different cycles and I find seedlings start to get leggy and spindly without a rest cycle. Seedlings may be different than growing something to maturity.

[MysticGardener67]

Grow seedlings as per normal then perhaps decrease the dark cycle to perhaps 18/6 or 20/4?? I think there may lso be a bit of a temperature component as well... Dunno, wish I had the resources to experiment on this.