Agriculture Reference
In-Depth Information
combination of both gives the best results. Also important in your choice
of lights are the reflectors.
HPS bulbs are available in 150, 250, 400, 600, and 1000 watts. MH
bulbs come in 175, 250, 400, 1000, and 1500 watts. The HPS lights provide
more energy in the red part of the spectrum, which promotes blooming
and fruiting, whereas the MH lights are more intense in the blue part of
the spectrum causing rapid growth. Commercial greenhouse growers will
combine MH and HPS lights for seedling growth to be sure that the entire
visible light spectrum is available to the plants. This is not practical for
indoor growing. Hobbyists have found that MH light has a wider spectrum
and therefore is more useful for indoors where no natural sunlight is pres-
ent. HPS lights are better to supplement sunlight to extend the day length
or to increase intensity during cloudy periods. The lamps cost from $20
to $100.
Some manufacturers now make a “conversion lamp.” This permits con-
version from HPS to MH. The HPS bulbs are made to operate with MH
ballasts. You can interchange the bulbs using the same ballast and fixture.
The fixtures cost about $200.
Over the past 5 years or so the compact fluorescent lights have been
emphasized to save electrical consumption. Now many of these lights are
sold specifically for the growing of plants. For example, Sunlight Supply,
Inc., markets these compact fluorescent lamps in red, blue, and dual spec-
trum. These lamps are available in 125-watt, 200-watt, 250-watt, and 300-
watt sizes. The red lamps are recommended for flower production and the
blue for vegetative growing, whereas the mixed spectrum is for plants from
start to finish. These lights, being 110 volt, fit into standard mogul base
sockets so do not require any ballast as do HPS and MH lights. These
lights are placed in highly reflective textured aluminum reflectors to give
maximum reflection and diffusion of the light (Figure 3.2). These bulbs
FIGURE 3.2
Compact fluorescent light with reflective textured aluminum
reflector. (Courtesy of Sunlight Supply, Inc., Vancouver, Washington.)
