Professional Marijuana Grower September-October 2017 Issue | Page 24

it enters the flowering stage. Some growers will increase the light energy incrementally as the plant grows in the flowering stage, but many growers find that starting with the higher light intensity (corresponding to the plant’s finishing size) so the plants can “grow into” the space is the most effective way to achieve the best results. Another aspect of lighting intensity is the distance be- tween the artificial light source and the top of the plant canopy. The inverse square law states that the farther light travels from its source, the more it diminishes. Put another way, when the plant canopy is farther away from the light source there is less usable light energy available to the plants. However, due to the extreme heat and intensity of some artificial light sources, plants can become damaged if they are placed too close to the light source. The best way for a grower to make the most ef- ficient use of his or her available light energy is to place the plants as close to the light source as possible without causing damage to the plants. Bleached or white flower tops are strong indicators that the plants are getting “over saturated” and are too close to the light source. Artificial Light Technologies for Flowering Marijuana There are a few different light technologies that can be used successfully to flower cannabis plants. Each technol- ogy offers its own advantages and disadvantages. Some garden set ups are simply more compatible with certain lighting technologies than others. In fact, the grow room and the type of growing system being used are both key factors when determining which lighting system would be the most efficient choice. High Intensity Discharge (HID) High intensity discharge lighting includes both metal ha- lide (MH) and high pressure sodium (HPS). HID lighting consists of three components: the ballast, the reflector or socket, and the bulb. Ballasts can be specific to the type of bulb (MH only or HPS only) or they can be switchable, or “smart” ballasts, and have the ability to operate either type of bulb. There are also double ended HID bulbs which have increased efficiency and longevity over other bulbs in the HID category. HID lighting is still the most popular choice for flowering cannabis for a few reasons. First, this technology has been around for a long time and is used in other indus- tries. This means there are many manufacturers which helps lower the cost and creates newer, more efficient de- signs. Initial cost and reliability are not the only reasons marijuana growers continue to choose HID lighting. High wattage HID fixtures are very intense and are capable of penetrating deep into a plant canopy while also cover- ing a large area. Due to state regulations, many medical marijuana growers are allowed a limited number of (Continued on page 28) 24 • Professional Marijuana Grower SEPTEMBER/OCTOBER 2017