Re: Observations, and Resulting Questions

Bob Beer (bbeer@u.washington.edu)
Tue, 8 Jun 1993 09:35:30 -0700 (PDT)

>
> In the context of recent postings on halogen lights,
> I'd like to know if they offer an advantage over fluorescent
> grow-lights for smaller collections. My plants seem to
> do very well with the fluorescents. My collection is small
> enough to be covered by eight 48" long tubes.
>
First (just to make sure we agree on what we are talking about) it is
halide lights, not halogen lights, which are useful in growing plants.
As for comparing them with fluorescent - no comparison!

Fluorescents are fine for small plants which don't grow over a few inches
tall such as low growing droseras, pings, etc., and baby Nepenthes that
have not yet started their vining growth. The problem comes in when you
want to grow taller plants - the intensity of the light decreases
dramatically with distance from the bulbs so that if you tried, for
example, to grow a tall Sarracenia under fluorescents, the light intensity
would be sufficient only at the tops ofthe pitchers, while the new growth
would not receive enough light for proper formation. You would have the
same problem with vining Nepenthes.

With a 1,000 watt halide, on the other hand, you grow things at least 3
feet from the bulb, and distances of 5 or so feet pose no problem. (I
have a passiflora vining all around the basement wall, blooming, under a
halide - My friends grow stapeliads and bloom them with no problem,
tomatoes will fruit...etc. etc. etc. and of course our friends in the
illegal substance business find them useful too).

HID light is produced by an arc of electricity in a glass envelope. They
come in two types - halide and sodium. Sodium light is more orange, and
is more useful for ripening fruits, etc. It tends to produce unnatural
colors (over production of reds) in most of the carnivores, so it is the
Halides we are interested in for our purposes. They tend toward the
blue-yellow range.

The only real disadvantage of halides I can think of is the cost - the
setups do not come cheap, but you can sometimes find used units for a
savings. The bulbs themselves are expensive but are guaranteed for a
year, and in practice will last around 3 years with loss of intensity
starting after 1 year.

I would go for 1,000 watt if you have the space. If you don't have it,
then get a 400-watt. Anything less costs about the same, and you get much
less intensity.

Another thing to keep in mind is that HID (High Intensity Discharge)
meaning halide or sodium bulbs - are not pretty, subtle lighting! They
are not the thing you want to have in your living room unless you make a
decent screen to keep you from looking at the bulb. The clear bulbs are
harder on the eyes if you are working under them for long periods - the
phosphor-coated ones are gentler, but I would still wear a visor or a
baseball cap if I were going to be under them a lot.

One last thing - these bulbs produce quite a bit of heat, so 1) don't hang
them so that the heat will build up - at least 1 1/2 feet from the
ceiling, and 2) be very careful when spraying and watering, that no water
splashes on a bulb, which will make it break, and the high vacuum inside
makes them implode - which is no better than an explosion! (Flying glass)
The outer bulb protects you from the ultraviolet rays produced by the arc,
and with this gone, you can be "sunburned." It can damage your eyes
especially, so if you break a bulb while on, get the hell out and turn off
the power immediately! (I have never seen this happen, but it is
something to be careful of).