HID stands for High Intensity Discharge. High Pressure Sodium (HPS) and Metal Halide (MH) are two types of HID bulbs that are good for indoor growing. MH bulbs produce light in the blue spectrum. This light is better for plant growth during the vegetative stage as it promotes stem, branch and leaf growth . HPS bulbs produce light in the orange to red spectrum. The light produced in the orange to red spectrum triggers the release of plant hormones used in the flowering stages. You can usually expect higher yields when growing with HPS bulbs.
High Pressure Sodium (left) and Metal Halide (right) Grow Light Bulbs
High Pressure Sodium (HPS) Grow Lights
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Metal Halide (MH) Grow Lights
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