One of the biggest advantages to indoor gardening is the regulation of plant growth through the use of artificial sunlight. The most commonly used grow lights are metal halide, high pressure sodium, and fluorescent. Each has its advantages. Both metal halide and high pressure sodium grow lights are high intensity discharge, which mean the light they produce has a better ability to penetrate the plant leaves.
Fluorescent grow lights can grow plants indoors, but produce much smaller plants and are generally considered to be far inferior to both metal halide and high pressure sodium grow lights. Fluorescent lights are most often used with seedlings or clones, as the light produced is gentler on fragile plants.
Metal halide grow lights should be used for the vegetative stage of plant growth. Metal halide grow lights will produce strong light in the blue and white spectrum which effectively mimics a typical summer day. High pressure sodium grow lights will produce strong light in the red spectrum which mimics the angle of the sun during fall. When your plants are ready to start flowering you should switch from your metal halide grow lights to your high pressure sodium grow lights.
This is the time to use your digital timer to switch the grow lights cycle from 24 hours of constant light to 12 hours of light and 12 hours of darkness, which tells your plants the days are shorter, the spectrum of light is changing and its time to flower before it becomes winter.
It is a common myth that plants can’t utilize more than 12 hours of light per day and require a dark period. This isn’t true. Try to imagine a plant’s growth cycle similar to an animal’s, the more you feed it, the fatter and bigger it gets. If you never decided to switch your grow lights to 12 hours of darkness your plants would continue to grow until they reached an unmanageable size!
We recommend you start the flowering stage, which is when you start the 12 hours of darkness, once your plants reach 10-18 inches in height. During all stages of growth your grow lights reflector should be around 5 inches from the growing tips of your plants. Since the reflector stays cool to the touch there is no risk of your plants burning. Move the grow lights reflector up as your plants continue to grow taller.
Another advantage to indoor gardening is the use of hydroponics, which means growing without soil. Believe it or not, growing plants in water is very easy, and requires little effort to maintain proper nutrient and pH levels. If you wish to use soil, you may, but you will see between a 100-400% increase in growth with hydroponics. The reason for this massive difference is your plants are constantly being provided with all the nutrients, water, and trace elements needed to become large and healthy.