Re: HID Lighting

From: Phil Wilson (
Date: Tue Dec 21 1999 - 06:12:43 PST

Date: Tue, 21 Dec 1999 14:12:43 +0000
From: Phil Wilson <>
Message-Id: <aabcdefg4220$foo@default>
Subject: Re: HID Lighting


I'll try to keep this brief!

><<Has anyone got any experiences to share with either Metal Halide or
>High Pressure Sodium lighting with CP's?>>
>I use both quite frequently and have had great results. My
>recommendation is to use sodium if the lighting is supplemental, (to
>natural light) and to use Metal Halide if the lighting is the sole
>source of light.
>I find that HPS (sodium) will start to produce elongated stems and wild
>blooming on some plants if it's your only light source. When used as
>supplemental lighting, in a greenhouse for instance, you can get some
>incredible colors and growth out of plants. I've produced the largest
>and most colorful Venus flytraps ever this way. Metal Halides are just
>good all-around, but are not as bright.

Essentially MH lighting is richer in the blue (UV) spectrum than sodium
lighting. High pressure sodium lighting (Son) is richer in the IR
spectrum but is weaker at the UV end. Commercially Sodium lighting is
used to promote flowering in bedding and house plants.

Blended sodium lamps are now available specifically for horticultural
use which make son lighting more attractive as an alternative to MH for
replacement or supplementary assimulation lighting.

The Son agro has been available for several years now. The
manufacturer's claim a 30% increase in the UV spectrum over a regular
Son-T lamp. Even more recently a new lamp has been developed, the Son
Planta which has a 40% increase in the blue spectrum.

>From what I have been able to obtain from the manufacturers, the Son
Planta has a virtually equivalent light output to a MH lamp. The MH lamp
has several disadvantages over the sodium lamp. First it has a tendency
to explode and should never be used where people have regular access
without a wire guard around the lamp. The wire guard will most likely
decrease the light output of the lamp.

The MH lamp also has a shorter lamp life. The light output of all High
Intensity Discharge (HID) lamps declines over time. For effective light
output an MH lamp should be changed about once a year (based on 365 days
@ 16 hours a day). A Son lamp should give last at least twice as long.
The rate of decline in light output for the Son Agro and Planta lamps is
substantially less than the Son-T lamp. A Son Planta lamp should give at
least two year's life before it needs replacement. If you are prepared
to monitor the light level with a lux meter you can keep them going for
longer than this.

Finally, a sodium lamp will give more light per Watt of energy. I have
heard figures as high as 25% extra over MH lamps from the manufacturers.

>I recommend 400 watt units if you can afford them. They seem to provide the
>best value for the investment.
400W lamps are definitely the best unit to go for. Here in the UK and
Europe they are virtually standard in commercial horticulture so tend to
be available at a good price. Bear in mind though that the lamps will
need to be mounted at least 900mm above the growing area and will cover
a larger area than the average terrarium. At 900mm the light pool will
be approximately 1.5 x 2.0M. This can be enhanced and the size probably
increased, if a specific growing area is constructed using reflective
white surfaces. Higher mounting heights will obviously increase the
light pool size but will decrease the light level. For growing most
carnivorous plants I would not recommend a mounting height much in
excess of 1.5M.

Phil Wilson
My Sarracenia plant list is now available at

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