# Lighting for lettuce, kale, etc in a greenhouse



## pengyou (Jun 22, 2009)

I will be putting a hydroponics setting together either on my balcony in a hoop type greenhouse or in my living room against an empty wall. In either case, additional lighting is going to be necessary. I am only looking for a 2-3 year solution, because I will be moving after that. I have searched a number of pages and most people now are trying to push me towards the LED lights. I have found a couple of older posts, however, that said that some variations of fluorescent lights are not only adequate for green leafies but that they thrive on them, and they are quite a bit cheaper. I am interested in maximizing the environment to see how fast a turn around I can get and still have the plants full and colorful. I am ultimately trying to find out how big (actually) small an area it would take to provide veggies and fruits for 2 people, and what kind of equipment is needed.

Any advice?


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## Belfrybat (Feb 21, 2003)

In a hoophouse, the only additional lighting you need for greens is when they are germinating and in the initial growth stage. When I had a greenhouse, I used regular "utility" fluorescent lights -- probably around 2700K, although they were not marked. When raising plants in the house, I mix both daytime (6500K) with cool (2700K) so as to get the whole light spectrum. 

There are many webpages out there for cannabis growers, and they have all this down pat. I'm not going to link here as it's probably against forum rules, but do a search on the subject. You might also think about hydroponics if you are growing plants to maturity inside.


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## pengyou (Jun 22, 2009)

Yes, I am going to do hydroponics, but what will I need in the way of lighting if I do it inside? I only have room for it in a place with indirect lighting.


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## Belfrybat (Feb 21, 2003)

http://www.offthegridnews.com/2012/10/15/growing-vegetables-indoors/

Do a search for growing cannabis indoors -- that is where I got my lighting requirements and other good info from. I actually purchased my lights from a website for cannabis growers.


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## gweny (Feb 10, 2014)

If you install a 2-bulb fluorescent light fixture using one cool and one warm bulb it will work saving you tons on expensive grow lights. Consider adding a small tomato plant to control aphids as well? The tomato will need a heating mat to keep the roots at around 80F.


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## ||Downhome|| (Jan 12, 2009)

what you use for lighting really boils down to a couple things, space and your electrical circuits.

Florescent work great. I prefer just cool white bulbs myself.
Plants tend to stay squat and not lanky which is beneficial inside.
Newer fluorescent are more efficient then year ago.
1 shop light in a 4x4 room won't accomplish much.
Lights all have lumen ratings, and a 4' double florescent gives on average 3200 lumens.
So that one light covering 16 sq feet (4x4) ( 3200/16= 200 lumens per sq foot) 
Enough for some house plants to stay healthy but not to much growth.
Most sources recommend 800-1200 LPF. 
So you would need 10 lights to reach that higher number.
Your electric use would be around 350 watts per hour of use, with a total of 32000 mean lumens.
The main benefit of florescent is they don't generate much heat and distribute light more evenly.
The draw back is the light has a high fall off, I.E you have 3200 lumens at 1" from the bulb but 600 6" away(thats just an example,I forget the actual numbers).

So that brings us to HID lights (metal halide and High pressure sodium) 
These are preferred for Indoor gardens as the are not as bulky, easier to move.
More efficient in light production (at least they use to be, 4 foot floresents use to use 40 watts per bulb , so my above exaple would of been 400 watts back when)
A 400 watt MH produces 40,000 lumens and a High pressure sodium 50,000.
1000 what bulbs considerably more.
They also do not have the high light fall off that florescent have.
The draw back is the heat produced. You have to maintain at least a foot between plants and lights.
The light is not as evenly distributed, you over come that with more lights spaced to distribute as evenly as possible to maintain a consistent growth.
so rather then 1000 watt lamp for a space 2- 3 400 watts lamps.

What ever lights good reflectors make the most of them.
You also want you walls to be reflective, flat white paint works as well or better then anything else for the purpose. 

that pretty much the basics for Indoor garden lighting, you do not necessarily have to buy something over priced either, hid lights are available on Craigslist all the time for cheap, and you can easily convert them to a remote ballast use.

regular old shop lights and a standard cool white if you go that route, or the CFL with reflectors work as well, I made a few hoods from ceramic light receptacle attache to galvanized sheet spray painted white and curved over to make the hood. 

They have 4 receptacles each and 20 watt CFL's about 2' long and 1' wide. 
giving me a total of 9320 lumens, I use them in a metal wardrobe Cabinet that a 4' light would not work in. I have it set up as 2 levels 1 light per level and do cuttings in it.

You need to be sure what ever route your wiring can handle the load, if not your asking for a fire. Happens all the time.

You will also want to have ventilation and circulation system to keep your plants growing well. 

Hope this helps! Best of luck.


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## Tyler520 (Aug 12, 2011)

First off, cannibis blogs are full of bull-----, to put it bluntly - potheads have no idea what the hell they are talking about.

Lumens, for example, are NOT what you want to use to measure energy on the canopy, because lumens are a measurement of human-perceived brightness, which means nothing to a plant.

there is no correlation between or formula for the energy required to grow a plant, and lumens

Rather, you should be measuring in the wattage hitting the plant. And if you want to get extremely picky, you would measure micromoles per square meter per second.

Lettuce will have great growth with 50 Watts/m2 for 14-16 hours a day.

a head of lettuce takes up approximately 1 square foot, so you can get about 9 heads of lettuce within that square meter.

fluorescent lights can be placed as close as 3 inches away from the canopy, so you wont have to worry about falloff, which is inverse squared: 25% power for every extra foot of distance away from the canopy


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## ||Downhome|| (Jan 12, 2009)

I'll stick with the lumen formula. 

Watts does not mean much to a plant either... 

You can separate plants into full sun,partial sun and shade.

Brightness means far more to a plant then you think.

Different lights put out different amounts of light per watt, as detailed in my post above.

A hid 2 foot above a plant will still deliver more light to a greater depth then the florescent, besides economy of light production , I think the over all investment (cost) per watt and light output is less in the long run as well.

The real issue though is heat. 

The Fall off means a lot too when raising something that will reach a moderate height.

What happens to anything below the canopy if there's not enough light reaching, the plant kills it off. 

Take two cuttings from the same plant, strip all the lower stuff off... tell me which does better in the end?


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## Danaus29 (Sep 12, 2005)

I pay no attention to warm white/cool white bulbs. I use the daylight bulbs in my set-up. I've done well with about 10 hours of light. Spinach will bolt while in the seedling stage if the lights are on 12+ hour a day. Keep the lights within a foot of the top of the plants. Some people say keep it within a few inches but I've done fine with about a foot. I've got 4 tube florescent fixtures. Not hydroponics but I've grown a lot of lettuce in my basement.


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