The light cycle is set for 12 hours because I grow short-day periodic strains. These flower when the length of daylight drops below 12 hours per day. I will begin harvesting my plants 6 to 7 weeks after the lights are set to 12 hours. The lower flowers are harvested about 2 weeks later. For some stains like Golden Tiger v.3 I get three harvests.
Wide spectrum, 2000 watt (rated), LED light in both tents provides the intense, well balanced light needed to maximize yield, trichome production and the numerous terpenes in the plant. The buckets are filled with nutrient solution based on the schedule on the Nutrients page under Environment.
Two 1000 watt (rated) LED in tent A 
To prevent burning the leaves the Mars light needs to be farther away from the plants.. The hood focuses the light on a smaller area. 
2000 watt (rated) Spider Farmer LED in tent B. Excellent coverage at 2 1/2 sq. foot. Greater density of LED diodes around the edge evenly distribute the light. 
The control for the dimmer on these lights is on top and cannot be removed. I had to extend the cord to reach the regulator.
Flower Development
When a cannabis plant begins to flower it will exhibit white hair-like structures emerging from these new flowers. They are often incorrectly referred to as pistils but are in fact stigmas. Pistils are the part of the plant containing the reproductive components, from the pistils the stigmas grow. Stigmas are the only part of the pistil which is visible, the rest is covered by a small leaf called the bract. The stigmas role is to catch pollen and pull it into the pistil/ovary to create a seed. The longer the pistil is denied pollination from a male, the more it will produce cannabinoid and terpene-rich resin in an attempt to trap pollen. As the plant matures these stigmas will begin to turn brown and are used as an indicator of when to harvest the plant.
Each new plant in the tent will have 4 (or 6 if I only have 2 buckets in the tent) main stems. Each of these stems will have a few lower stems because I quit removing them a week before the flower stage started. Each strain grows at a slightly different rate. When the tops of a plant are over 1 1/2 inch below the tallest plant I set this slower growing strain on bricks. This insures all of the plants will get the same amount of light.
During the first week I remove the upper fan leaves to keep them from covering the the developing stems. Using wires I also pull the main stems away from each other to provide plenty of space.
New stems will grow rapidly and need to be pulled below the main stem. Each day I need to bend some of these flexible stems when they grow taller than the main stem. These wires are usually removed in the next day or two. The stems will usually thicken and grow slower from then on.
Flowers will grow from the nodes and each stem tip, forming colas in a variety of shapes depending on the strain. Essentially the flowers will grow stacked upon each other with new flowers pushing out between the first flowers to emerge. Due to phenotypic variation in hybrids you could plant seeds of these same strains yet the flowers and other physical characteristics might vary from my plants. Breeders work hard to keep phenotypic variation to a minimum but biology is somewhat messy. This is one of the reasons I prefer to use clones, I know how each plant will grow.
By around 4 weeks the stems will stop growing. Flowers will continue to form, filling out the colas. I will need to keep the upper fan leaves trimmed to allow light to the lower colas.
It is important that you quit trimming fan leaves when trichomes begin coating them. From this point on you could seriously damage the plant by cutting too many of these leaves.
Sometime during the fifth week the flowers will still be forming in the colas but few, if any, fan leaves will appear. As tops get heavier they will bend and spread out allowing more light to lower flowers.
The longer you wait to harvest a plant, the THC content will rise, however so does the feeling of drowsiness when used. For Indica flowers I wait as long as possible before harvesting to accentuate the high of these strains. Sativa leaning hybrids need to be harvested when few new flowers are being produced and some of the stigmas are still light colored.
indica
sativa
I do not flush my plants in the last week of flowering. Some growers remove the nutrient solution and replace with water every couple of days during the last week of flowering. A very well done study from The Atrium has shown that flushing has no affect on the chemical composition of the plant. For an interesting look into this research go here. High Times has its own take on the practice.
Growing medical cannabis 