Grow light systems – Overview
There are basically 2 categories of light systems that are available in order to get your Cannabis plants, the MH/HPS combo and LED systems.
Before going further it’s important to define each so everything is clear
Metal Halide and High Pressure Sodium Lighting System
Metal Halide and High Pressure Sodium and 2 types of light bulbs that provide the full light spectrum needed for a healthy plant.
While the MH bulb provides a large spectrum, the HPS bulb provides much warmer colors, let’s look at each in detail
Metal Halide (MH)
As you can see on the graph on the right hand side, the MH light bulb provides a full light spectrum with a peak in yellow wavelengths.
Although it can be used through the lifecycle of Cannabis generally it is only used during the vegetative stage since that is when the plant mainly needs the blue light spectrum for growth.
High Pressure Sodium (HPS)
HPS light bulbs focuses on a much “warmer” light spectrum than it’s MH counter-part.
There’s very little short (violet/blue) wavelengths, with a concentration from the hot greens to the cooler reds.
These wavelengths are well adapted for your babies once they’ve entered the flowering stage as they replicate well a hot summer sun.
Growers generally operate the change between the MH bulb and the HPS bulb during the stretch, once the plant has stopped vegetative growth and developed multiple bud sites.
Light-Emitting Diode (LED) Lighting System
LED systems may vary depending the type of diodes on your system. Generally these systems provide a large light spectrum, similar to the MH bulb, as you can see on the image aside.
As much as we could tell LED systems do seem to render less flowers in comparison to a MH/HPS combo. Is it linked to the light spectrum though, hard for us to say for sure..
Edit: Newer generation LED systems have a high performance spectrum which can definitely compete with an MH/HPS lighting system