High pressure sodium (HPS) lights are the only lights comparable to metal halide
growlights. They have good spectral distribution, but sodium lights can not compare
to halide in the blue end of the spectrum. Just in the same way, Metal Halide
lights can’t compete with HPS (high pressure sodium) in the red end of the spectrum. Sodiums are
particularly high in the yellow and red regions of the spectrum. This is the
type of light fruiting and flowering plants like best. Because of the focus on
red light, some varieties of plants grown with sodium lights alone can become
elongated and leggy.
High pressure sodium lights do, on the other hand, stimulate flower and fruit
production more efficiently than halide, making them an important light source
best used in conjunction with metal halide either in addition to, or cycled
together. HPS (high pressure sodium) bulbs also have a much longer life expectancy than halides,
lasting up to two (2) years!
