It is a well-known fact that marijuana plants use light as energy. Special organs inside leaf cells called Chloroplasts secure the red and blue light from the visible spectrum of light and use those to start photosynthesis. During photosynthesis, plants take certain elements from air and water to produce sugar while also releasing oxygen.
The sugar is then used to power metabolism (or, the process of living) and to build tissue (e.g. flowers, stems, etc.). More exposure to light helps the chloroplasts function even faster. In concert with sufficient amounts of watery CO2 and other nutrients, the plant will increase production with increased light exposure. This usually culminates in faster growth and larger yields.
Marijuana plants grown outdoors thrive in full sunlight. Indoor plants, however, need around 40 watts of HPS or MH light per square foot for full, tight indica buds. Sativa buds need at least 60 watts. Both MH and HPS lamps can be used for the vegetative growth period. HPS light is beneficial for flower growth during the flowering period. Fluorescent lights can be used for both vegetative growth and flowering. During vegetative growth, use cool, white fluorescents and, during flowering, use warm white fluorescents. Download my free marijuana grow bible for more tips about growing marijuana plants.
What if some of the plant's leaves touched and were signed by the fluorescent light? When using this method to grow, it's important to keep the marijuana plants at least a few inches (about 5 cm) away from the lights. Sometimes, the leaves will reach up and touch the light causing brown spots on the surface of the leaf. If this happens irregularly, it won't cause significant damage to the plant. Of course, if the leaf is no longer usable, you should remove it from the plant. If light damage happens more often than you'd like, try placing a wire barrier around the tube so that the leaves will not touch the light.
What is you can't get forcing flowering to work. That is to say, the plant will not flower despite the fact that the light cycle was changed to 12 hours of darkness/12 hours of light a few weeks ago? There are three probable causes of this problem: the light has stayed on too long, the room has a few light leaks, or the light was turned on during the dark time. Try to maintain a strict light schedule and use a green light in the garden if you have to enter into during the dark period.
Dark cycle interrupted
What if the lights were left on for one or more days? If the light is only left on for a single day, you won't really see much difference. But, if the lights are left on for a few days straight, the plants might start regressing back to vegetative growth during the early stages of flowering. Too much light exposure has less effect as the plants near maturity.
Get the cycle back to normal as soon as possible. This will prevent the plants from incurring any more damage. If the plants have reverted even a little bit to vegetative growth, the buds will obviously take a little longer to reach full maturity.
What if the lights were left off for one or more days? You will see the buds ripen faster but simply turn the lights back on an continue the normal flowering schedule until the buds are ripe.
What if the lights were turned off and on irregularly? You'll find lanky, irregular buds and an increased probability of hermaphroditism. See Hermaphroditism for more information. Use a timer to ensure that the light regimen remains consistent and helps the buds grow and gain potency.
What if plants will not flower indoors? Marijuana plants that are grown indoors can be induced to flower with uninterrupted dark periods that last 12 hours a day for 4 to 5 days. Beyond that, most varieties require that you continue enforcing this regimen. The light deprivation cycle should follow a strict schedule, starting and ending at the same time every day. Lights should be set on a timer to avoid any mental lapses or human error. See also Forcing Flowering.
If you want to start growing, download my free grow guide and order some marijuana seeds. All top quality marijuana seeds are available in my marijuana seed shop. We ship seeds to the US, CA and many other countries. For any growing related question please visit the marijuana support page.