GROW LIGHTS FAQ (Last update, January 12th, 1995)

Maintained by Samoka Z. Boul

  The purpose of this FAQ is to help limit the spread of misinformation
 regarding effective artificial lighting systems, and help those who
 choose to grow plants under artificial lighting make an informed
 decision before buying a lamp.

  Most of the information contained in this FAQ comes from printed
 sources, and some from electronically distributed files.  Very little
 comes from my own experience, as I have not owned, used or examined
 most of the systems discussed here.

   This FAQ is not going to tell you how to use your lamp, that
 information can be found in most grower's guides.

Introduction:

  There are three major types of lighting systems available right now:
 incandescent, fluorescent, and high intensity discharge.  Incandescent
 lights are horribly inefficient (especially the screw-in "grow bulb"
 type) and really not an acceptable option for plant growth.  Although
 they are inexpensive to purchase, their cost of operation makes them
 the costliest source of light. 

Fluorescents:

   Until the early 1980's most indoor growers used fluorescent lights to
 illuminate their garden.  These tubes have tremendous advantages over
 incandescents.  They emit about 3 times as much light as an
 incandescent (given the same wattage), and the light spectrum is one
 that plants con use more effectively.
   However, they do certainly have their limitations.  Light is emitted
 over a large area, so it is not concentrated.  Because of this, the
 lights have to be hung very close to the plants (usually within 2" or so 
 from the grow tips), and constantly moved to accommodate plant growth.  
 This makes garden maintenance rather difficult, even when the lamps are 
 hung on chains.
   Florescents are, however, very useful in cloning, and starting
 seedlings.  Because in these stages, a plant is not growing vertically
 very quickly, the disadvantages of moving the lights are reduced.  They
 also put out a more gentle light than the HID lamps, and release less
 heat.  The fact that they produce less heat is very important to those 
 growing in enclosed and not-especially-well ventilated spaces.
   If you choose to use fluorescents, it is best to purchase the 'cool
 white' variety.   The ones that are sold as grow lamps (including
 grow-lux, vitalite, etc.) are much less efficient than a standard
 fluorescent, and just do not put out enough light to be useful.  The
 slightly different spectrum produced by these lamps does nothing for
 most plants.  Some growers have reported excellent results by using a 
 mixture of cool-white and warm-white lamps in a florescent fixture.
   

High Intensity Discharge Lamps (HID's)

   High intensity discharge lamps are easier to use, and more
 efficient.  Low wattage HIDs are sometimes sold for household outdoor
 use.  Large Wattage lamps are used for lighting streets, parking lots,
 stadiums and other large areas.  They come in two basic flavors:

    METAL HALIDES or MH lamps emit a white light that looks slightly
     bluish.  They are used to light stadiums, convention centers,
     gymnasiums, and other large areas where a natural looking light is
     desired.

    HIGH PRESSURE SODIUM or HPS lamps emit a pink or amber light.  They
     are used for lighting parking lots and other areas where the color
     of the light is not important.  HPS units are much more efficient
     than MH ones, producing more light and less heat per watt of energy
     consumed.  They are often used alone with no detrimental effect on
     the plants, and will promote faster plant growth than MH lamps
     during both vegetative growth and flowering.  Combinations of
     bulbs are _NOT_ required, as the HPS lamp does produce all of the
     light spectrums necessary for healthy growth.
        There is a relatively now type of HPS lamp that has become 
     available.  It is called the San Agro lamp (Look in _Grower's Edge_ 
     Magazine for more than a few distributors.  Basicly the designers of
     this lamp took a 400w HPS lamp, and added another 30W element to it, 
     However, this new element puts out blue light, to help fill in the 
     parts of the spectrum that a standard HPS is missing.  I've never 
     actually seen one of these bulbs, so I can't tell you about how 
     efficient they are, but if a Hydroponics magazine thinks they're 
     terriffic, I can't disagree.

   MH lamps are available in 175,200, 400 and 1000 watt sizes.  HPS
 lamps come in 50, 75, 150, 400 and 1000 watt sizes. San Agro comes in 
 430w only, but it works with a 400w HPS ballast. Each lamp
 requires its own ballast, which comes with the fixtures that are
 designed to use these lamps, and are also available separately.

   The following chart shows how much light each lamp emits, and the area
   that it covers adequately:

        Lamp                            # of Lumens             Sq. Ft
        ----                            -----------             ------
        4'FL (CoolWhite-40W)             2,960                  1-2
        8'FL (CoolWhite-75W)             5,800                  2-4
        MH 175W                         14,000                  5-10
        MH 400W                         40,000                  12-20
        HPS 70W                          7,600                  3-6
        HPS 150W                        16,000                  6-11
        HPS 400W                        50,000                  15-30

   Gardens should receive 1000-3000 lumens per square foot.  Successful
 gardens usually are lit at around 2,000 lumens per square foot.  During
 the vegetative stage, plants stretch out when they receive low levels
 of light.  During flowering, the flowers are looser and sparse.

   So what is the best lamp for grow6ing?  It depends on your budget.  HPS
 lamps are by far the best overall, but they are also the most costly to
 purchase and setup (although some less honest growers have a tendency
 to steal them from college campuses and the like).  However, they are
 the cheapest to operate, and the utility savings does eventually add
 up.

   A quick warning:  At least in the US, there are large government
 agencies whose only purpose is to eliminate the growth of marijuana.
 Although purchasing a high powered lighting system does not mean that
 you will be growing pot (and many people grow other things
 artificially),  it is still not a really good idea to link your name
 with the purchase of one of these lamps (especially the larger ones).
 Go into the store knowing exactly what you want, pay for it in cash,
 and do not give them your name (or give them a false one if they even
 ask).  Most lighting distributors will not ask any questions.

   I wish you a healthy and happy crop.

- Samoka.

==
The author is a freelance writer/UNIX guru, who doesnt know anything 
about what grows under these lamps, except for Tomatoes,  living 
somewhere on this side of eternity.  Don't even think about asking for
an email address.

"Think about the future, for it is where we will spend the rest of our lives"