Lighting (MH or CFL) for lettuce and herbs

IcybergJune 30, 2013

For now, i am going to grow lettuce and herbs like basil, arugola and dill. Later on i will be adding peppers, tomatoes, cucumbers etc.

What kind of light would be best for my now (lettuce+herbs) and what would be best for me later(peppers, tomatoes, cucumbers etc.)? I was thinking of either MH or CFL.

I will be growing in Deep Water Culture system.

Best regards, Icyberg

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slimak

I just began growing veggies myself so I can't speak from experience, however I did lots of reading on the subject before choosing my lighting system. I guess first question is how big of a growing area you planning too have? Is it an area where possible fire is of great concern? Fire was a big concern for me and my growing are is only 2x4x6 feet so decided to go with t5 ho lights for the following reasons. MH and HPS lights give off a lot of heat so you need a good ventilation system to keep them in check. ...

    Bookmark   July 1, 2013 at 9:22AM
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slimak

... additionally you need to keep the plants farther from those lamps for that reason as well so you loose about 2-3 more feet of space on top. With fluorescent lights there is not much of heat issue and you need to keep the lights close 1-3 inches therefore you could have several lights stacked up vertically increasing your grow area.

Secondly, your choice also will depend on what type of vegetables you will grow. Leafy plants such as lettuce, herbs etc. need light for vegging. Fruiting plants such as tomatoes, peppers need light for vegging and flowering.

For vegging stage plants mostly use blue spectrum of light(apparently 430nm range is best for chlorophyll production) MH and Fluorescent bulbs are great for that. For flowering stage you apparently need mostly red spectrum of light(610-700nm range where 660nm is ideal) HPS lights are great for that purpose because most of their spectrum is in red with very little blue.

As far as flowering with Fluorescent bulbs I see that most people say that it doesn't work efficiently to get higher yields. That might be because the red bulbs that you get in hydrophonic stores are triphosphorus bulbs that are in the range of 610nm of the color spectrum and not higher.
However, there are bulbs available in the aquarium stores called "Red Sun" which put out 633nm. Those who use it swear by it but I can't say that they do work since I haven't tried them yet myself.

Another con that Fluorescent bulbs have is penetration of light through the canopy to the lower leaves. That's where you Lumens units come in. An MH bulb is much more powerful than Fluorescent lamp therefore you get bigger penetration. You could however improve the performance of Fluorescents by having light fixtures with reflectors and having reflective wall material in your grow area so the light bounces of and reaches lower parts of the plant.
You could use flat white paint, reflective films such as mylar, poly film or orca film(apparently it diffuses light best, doesn't create hot spots like mylar and has great reflective ability)

Hopefully I was able to help. If I'm wrong on something I'm sure the pros on this forum will point it out

    Bookmark   July 1, 2013 at 12:19PM
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slimak

One more thing that I'd like to add. Remember that different species of plants have different light demands. Some need 10 hours daily and some benefit of 16 hours daily. On top of that some that that you want to flower will also demand shorter periods of light. With Fluorescent lights it's easier to divide your area into sectors for appropriate needs. One shelf could be set to 10 hours of light, another to 16 and another for flowering. With MH you'll either have to grow everything at one same duration or have a lot of room to fit growing areas for at least vegging and blooming separate. I won't touch on power consumption and how each type of lamp performs, I'm sure there is someone who can help explain that. Good luck!

    Bookmark   July 1, 2013 at 12:34PM
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