indication that either of these theories holds
up. HPS lamps produce faster growth than
a combination of HPS and MH lamps.
There is absolutely no need to or
advantage to buying a MH unit. Plants
grown under HPS show some stem
etoliation (stretching) and ripen about a
week later. This is more than compensated
with a considerably larger crop.
Some fluorescent tube manufacturers
produce grow tubes which are especially
formulated to provide a spectrum of light
similar to the chlorophyll synthesis or
photosynthesis spectrum or a compromise
between them. The idea is sound, but grow
tubes produce only 35-60% of the light of a
cool white fluorescent, and less light
useable by the plant. One manufacturer
advertises Vita-Lite® and Optima®
fluorescent tubes which emit a light
spectrum color balanced close to the sun’s
spectrum. However, they emit only 75% of
the light of a warm white fluorescent.
COSTS
HPS systems are the most expensive to
purchase of all of the lighting units. MH
units are a little cheaper and fluorescents
are the cheapest of all. However, this is
figuring only the initial outlay. Factoring in
the cost per unit of light produced, the
positions are reversed. HPS lamps are the
cheapest, followed by MH lamps and far
behind come the fluorescents. In addition
HID lamps are considered easier to work
with in the garden and produce a better
crop than fluorescents.