Lighting Cannabis Indoor Growing


Key points:

  • Cannabis plants thrive on the right light
  • Incandescent lightbulbs are not suitable for growing Cannabis
  • Indoor growing allows greater control of the grow environment
  • Darkness is just as important as light
  • Color spectrum can affect vegetative and flowering stages
  • 12/12 hour light cycle will start flowering*

If you are starting to grow Cannabis for the first time then it’s vital to remember the importance of lighting and how it can make or break your growth.

Cannabis plants are not like your usual perennials. Unlike perennial plants that continue to grow and flower for over 2 years, the Cannabis plant is annual, meaning that it will live out its entire life cycle in the space of a year. Put simply annual plants are made for one thing… reproducing! Soon after flowering, annual varieties like the Cannabis plant will produce mature seeds before dying off during the autumn. Although they have died they leave hundreds if not thousands of seeds that can carry on the line during the next spring.

Photoperiod and Light Cycles

It is often said that most professional growers prefer to follow a 24/0 photoperiod. By leaving your lights on for 24 hours a day you can gain much better results and will hopefully get a much more vigorous stage of growth. This is often seen as key in attaining a greater yield with an indoor grow setting.

Definition: Photoperiod the period of time each day during which an organism receives illumination; day length.

That being said, other growers will tend to use an 18/6 photoperiod, meaning that your plants would be getting 6 hours of darkness each day. It’s worth saying here that you shouldn’t expect to get a greater yield from a shorter light cycle, indeed the opposite is true. However, having a quarter less light each day doesn’t mean that the yields follow the same pattern. Growers that do follow this pattern often favor the benefits of having slightly less maintenance and a much-reduced electricity bill (always something worth keeping in mind).

When your Cannabis plant eventually reaches the end of its vegetative growth phase, it is time to turn the photoperiod to a 12/12 light cycle. By having 12 hours of light and 12 hours of darkness you will force the plant into triggering a reaction that starts the flowering stage. The 12/12 light cycle should then be kept in place until the Cannabis plant almost reaches the end of its flowering stage and is ready to harvest

*It is worth noting here that the typical light cycles do not apply to auto-flowering plants as autoflowers will ignore the length of the photoperiod and flower after a set time, regardless of the available light cycle.

If you are growing your Cannabis outside then you will not need to worry about trying to change or control the light cycles, the Sun does a perfectly good job at that and your plants will start flowering naturally when the time is right.

Benefits of Indoor Cannabis Growing:

  • More control over the environment
  • Lighting can be moved closer or further away depending on the needs of your plants
  • The humidity of the grow room can be controlled
  • Growers can experiment with different cycles to change yield and grow time
  • Plants safe from strong weather conditions
  • Plants less vulnerable to attack from insects and animals
  • Types of Lighting for an Indoor Cannabis Grow

There are many different kinds of lighting available to indoor Cannabis growers and while each has its own benefits, some have more downsides than others.

Lights such as High-Pressure Sodium Lights (HPS) and Metal Halide (MH) are known for their ability to produce great levels of both light and heat meaning that although greater yields can be achieved, they are not really suitable for new growers or those looking to just grow a couple of plants. They also have the downside of needing to be well ventilated and using a large amount of electricity should you keep them turned on for too long.

Results can even be gained by using standard indoor Compact Fluorescent Lights (CFL), bulbs like

this can be found in Homebase or B&Q and is now becoming standard in most homes. Because they are so ordinary, people don’t realize that these bulbs can produce both the right temperature and light spectrum for Cannabis plants to grow.

So for novice growers and anyone looking for ease of use we’d recommend using LED lights as they use smaller amounts of electricity and are frequently smaller and less bulky than other types of lighting.

Light Emitting Diodes – LED’s

LED lights have only recently jumped into the spotlight (sorry) and have gained their reputation by being smaller, more efficient, and more technologically advanced than their bulky, power guzzling predecessors.

Their popularity isn’t just down to their efficiency, LED lights are becoming known for producing a wide light spectrum that means excellent yields can be achieved.

Benefits of LED Lighting:

  • They disperse heat better
  • Can affect both taste and smell
  • Has the potential to increase THC content
  • More efficient than any other bulb

Technological advancement means more efficiency in the future

Like all things, however, there are downsides. Many of the negatives associated with LED grow lights were down to a few bad companies selling them without actually having tested them on growing Cannabis first. This meant that many people have in the past found that LED lights were not suitable for growing mail order marijuana. The technology behind LED lights has progressed vastly since then and while there will always be the odd dodgy player trying to flog useless lights, the technology itself has now been proven to be good at growing Cannabis, you just have to pick the right ones!

Knowing this it would be safe to say that you should always read user reviews from other Cannabis growers when looking at purchasing any kind of indoor grow light.