In the grow industry there are a few types of bulbs available when growing and flowering your plants. It is important that you are giving your plants the correct spectrum of light at the correct stages of your plants life.

Metal Halide Bulbs (aka: MH) – Metal halide bulbs emulate bright summer sunlight and contain all the energy peaks at wavelengths of the visible spectrum. To plants this means quality simulated sunlight and photosynthesis at a level much higher than that which fluorescent lamps can achieve.

Use MH bulbs during the green vegetative stage of your plants’ growth cycle.

High Pressure Sodium Bulbs (aka: HPS) – Sodium grow lights 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.
HPS grow lights do, on the other hand, stimulate flower and fruit production more efficiently than metal halide bulbs, making them an important light source best used in conjunction with metal halide either in addition to, or cycled together.

Use HPS bulbs during (or to initiate) the budding, flowering and fruiting stages of your garden.

It is recommended to change your bulbs every 9 months or every 3 grows, as over this time the lumens drop. You and I cannot see the drop in the spectrum, but the plants do, so you will see less production and lower yields.

Insufficient light will result in weak plants and small yields.