That being said, when it comes to the flowering/budding stage, if you can fit a bigger light you will get significantly better yields/watt by using an HID or LED grow light!
The light from a Metal Halide appears a little bluish, and is well suited to growing cannabis plants in the vegetative stage
Cons of Fluorescents
HIDs are very well suited to growing cannabis and very easy to use once they’re set up. If your main goal is to get the highest yields possible, then HIDs are the way to go! However, they do require extra setup compared to the other grow lights because chances are you will need a fan to vent out heat from your grow space.
Note 2: Incandescent light bulbs (old fashioned light bulbs) are NOT suitable for growing marijuana!
On the other hand, if you plan to grow outdoor, your light cycle for flowering cannabis should also be scheduled for 18/6 or 24/0, but you will want to first keep them inside until all unfavorable conditions like freezing temperatures and frost have passed. After that, you can safely bring them out and allow them to grow and flourish naturally under the open atmosphere, relying on the sun’s natural light cycle.
Note that while in the vegetative stage, light is not the only means of growing large cannabis plants. If you are growing your plants indoors, you will need a well maintained grow room with a high ceiling.
To grow cannabis successfully indoor, you need to mimic the natural growth pattern. When you grow your cannabis outdoor, they start to develop buds (flowers) as the days gets shorter, and they receive a minimum of 12 hours of complete darkness. To do this, just switch your light usage from 18 to 24 hours of good sunlight daily down to 12 hours of light and also of 12 hours of darkness for the cannabis life cycle.
When marijuana plants are in the vegetative stage, keep them under a minimum of 18 hours of growing light (also known as 18/6). But if you are one of those growers that would like their plant to grow as big as possible, then you may keep them under 24 hour (24/0) indoor light.
Scheduling Your Light Cycles for Maximum Yield
Typically, most growers would start their cannabis plants indoors under lights before moving them outside to grow under the sun. Most growers would usually start either cutting clones or starting seeds during March or April, and would keep them under 18 to 24 hours of constant light before moving them outside in the early period of May or June.
But, once such risks are over, your plants will be in vegetative stage outdoor from the late period of spring down to late summer.
Of course, the plants will not stop growing or developing flowers at this particular instance. On average, the plants start doubling up in height and shape after they begin the flowering stage — this is true for both indoor and outdoor plants. However, make sure your cannabis plants are NOT exposed to light during the 12 hours they are supposed to be in darkness. Take care: floodlights and even street lights can seriously disrupt the flowering period.
Outdoor Vegetative Stage
For your plants to move from their vegetative stage to the flowering stage, they will need to be exposed to 12 or more hours of darkness each day to start flowering.
If you have plans to grow your plants outdoors, allow nature to take its course. During this time period, the cannabis plants will start to produce flowers naturally on their own, which usually happens after the 21st of June, as the days start getting shorter.