Maximum Yield Cannabis USA October/November 2018 | Page 75

Secondly, cannabis is classified as a short- day photoperiodic plant species, meaning changes in sunlight patterns directly dictate the seminal phases of a plant’s lifespan. As most cultivators know, the defining photoperiodic characteristic of cannabis occurs with vegetative and flow- ering cycles, in which 12 hours of uninter- rupted darkness causes a plant to flower. These light durations are indicative of late summer and fall sun cycles. Serious indoor gardeners must accommodate for the biological demands of cannabis and the plant’s accompanying changes in growth patterns related to lighting. In designing a lighting schematic for an indoor cannabis garden, growers must consider the advantages and drawbacks of a variety of technologies — making deci- sions between these can be difficult and often boils down to subjective preference. The primary grow lights on the market today are: fluorescent, metal halide (MH), single-ended high pressure sodium (SE HPS), double-ended high pressure sodium (DE HPS), and light emitting diodes (LEDs). Rather than focus solely on growroom infra- structure or the technical specs of specific lights, the following information is based on biological needs and growth patterns of the cannabis species relating to light sources. Vegetative and Flowering Stages W hen planning any cannabis grow operation — indoor, greenhouse, or outdoor — light is perhaps the most important variable to consider. Designing a functional and efficient lighting system in controlled environment agriculture can prove challenging. When considering indoor gardening, cultivators must weigh several important variables relating to infrastructure, budgeting, and plant growth when choosing the proper lighting plan for a successful cannabis grow. Physiologically speaking, there are several reasons why effective lighting is so important in growing cannabis. To begin with, cannabis has evolved to thrive in arid, sunny climates. Indoor growers are well advised to create envi- ronments and lighting schematics that match the ecological influences in which the DNA of cannabis responds favorably. Looking at the lifecycles of the cannabis species regarding photoperiodism, the most important factor to note concerning growroom lighting has to do with changing light requirements of both vegetative and flower growth. Each of the crucial periods of growth has specific requirements for lighting. These changing light patterns are indicati ve of seasonal changes in sunlight patterns, spectrums, and intensity. In the northern hemisphere, the vegetative growth period of cannabis plants occurs naturally in the spring and early summer months. Studies show that light wavelengths in this time of year present predominant blue spectrums. Under the influences of sunlight imbued with blue light wavelengths, cannabis plants naturally grow stout and strong during the vegetative photoperiod. As a result, grow lights designed specifically for vegetative growth seek to mimic the spectrums occurring naturally in the spring and early summer months. Traditionally, fluorescents and metal halides have been the grow lights of choice for vegetative indoor cannabis cultivation because they present predominant blue wavelengths. In recent years, LED lights have grown in popularity as the relatively new technology is trusted by growers to handle vegetative growth, which is not nearly as demanding as seen with flower production. Maximum Yield 73