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Growing Cannabis Indoors – Your Guide to the Right Lighting

There are some serious benefits to be had when growing your cannabis indoors. For instance, you may not have to buy grown marijuana anytime soon (probably never if you keep it up). You don’t end up relying on a shoddy guy around the corner who says he has ‘something’ for you but will deliver ‘something else’ when you pay up. And, you can grow your own herb very discreetly, without the neighbours ever taking notice.  

Let’s face it – growing cannabis indoors is really simple because it’s a strong and fast growing plant – no wonder some refer to it as ‘weed’ because it literally grows like a weed. Even if you grow it under ‘not the most ideal’ conditions, it’s still hard to mess up. Plus, the turnaround is reasonably quick – in just 4 month, you have a smokable product in your hands. 

Now, all of the above is true if you pay attention to one very critical element of growing your herb indoors: lighting.  

Although there are other elements involved when it comes to effective indoor marijuana yields, lighting is one of the most important ones because it’s going to be on your crop pretty much all the time. Mess this up, and you’ve messed up the entire lot and your investment as well.  

Cannabis needs lots of light to grow properly – although exactly how much light depends on the weight of your harvest – so the better the lighting, the more the harvest.  

For Starters: Indoor Marijuana Grow Lights Basics  

Since we’ve opted to do this indoors, we need to settle for a room that is 100% light-proof. Why is this important? Because we need to select the light and darkness hours according to set intervals so that the photosynthesis process can take its natural course.  

For example, during the vegetative phase, your plants will need to be exposed to ideal lighting conditions for a minimum of 18 hours, and consequently 6 hours of complete darkness. Similarly, during the flowering phase, you’re going to expose them to a 12 hours on/12 hours off cycle.    

For indoor production, LEDs or HPS lights work great. Go with 400-Watt lights for the vegetative phase, while 600-Watt HPS for the flowering phase per each square metre is a good starting point. However, we should point out that the extra investment in LEDs at this point is well worth it because they last practically forever. As a matter of fact, the technology has at long last caught up with the HID lamps that professional growers have been accustomed to for years.  

Another aspect to consider as far as lighting goes is reflective walls. White walls are, therefore, ideal. Reflective walls ensure that all the light remains focused on your plants while they are on. Dark walls can absorb a lot of the light which is counter-productive.  

By using a light timing switch, you can create the most ideal lighting conditions for your plant and make things easier for yourself.  

Your Lighting Choices for Growing Marijuana Indoors 

Here are commonly used marijuana grow lights you should consider – depending on your budget and cultivation needs, we’ve reviewed some of the key highlights for you: 

LED – Best Energy Efficiency 

Even though they are relatively new in the market, Light Emitting Diode growth lights have grown really popular among cannabis cultivators. The only downside: the initial cost. Nonetheless, if you’re willing to shell out a little extra cash, you should invest in LEDs due to their long life. Fortunately, with demand so high and LED being the preferred choice for new and expert growers alike, you might see price cuts sometime in the near future.  

Another benefit of LED lights is that they are quite small, making them not only energy efficient but space efficient as well. And, despite being small, their functionality is never compromised.  


  • No matter how long you want to use them, their running temperature will remain low. You’re never at risk of accidentally burning your crop if left unattended for longer durations.  
  • In terms of energy efficiency, LEDs are the undisputed best grow lights. They don’t need too much energy and still produce impressive amounts of light.  
  • As stated earlier, LEDs last almost forever; in fact, the average LED light lasts anywhere between an average of 50,000 to 100,000 hours at least.  


  • High initial cost, which tends to discourage most novice growers. However, once you take into account the benefits in the long-term, the relatively high price is easily justifiable.  
  • Some LEDs don’t produce as much light intensity as desired since they require such low energy to run; however, this is something that can be brand specific. Get 30-Watt LEDs and you should be fine.  

Fluorescent CFL– Best Compactness and Price  

Fluorescent grow lights are available in the CFL and T5 category. Compact bulbs, otherwise known as CFL, can be easily bought from your local hardware shop and work well for small or generally narrow areas.  

However, for professional-level production, you should invest in T5 grow lights (we’ll be discussing those right at the end) which can be found in a home and garden shop – these are characterised by their long, tube-like shape, just so you know.  

One thing to keep in mind about CFL lamps is that they are well-suited to small yields only during the vegetative and flowering phases. And even though T5 lights generally work well for small plants, they are not the best for the later stages.  

Fluorescent lights are your best bet for the initial seeding or growth stages. They are also the best lighting choice for cloning since the light isn’t very intense – it won’t burn your plants.  


  • These are really light on the wallet; in fact, the cheapest grow lights currently available. 
  • The cool temperatures produced by CFLs ensure that your plant suffers the least amount of stress. 
  • They are also a good choice for beginners who have a limited knowledge on cannabis cultivation. 


  • Not the best choice for large rooms, although just right for a single plant in a relatively small space. 
  • Strength/intensity of the light may be a problem; you can forget about getting large yields. 
  • Not the best grow light choice for the final stages of growth. 

Fluorescent T5 – Absolute Best Price and Good Quality  

Similar to CFLs, T5s are best known for their cool running temperatures, making them ideal for the propagation phase. The T stands for ‘tubular’ – or shaped like a tube. The number ‘5’ signifies 5/8-inch if a diameter.  

T5 lights are typically 2-4 feet long, although in most cases, they are used in groups of four. They also need a reflector which is hung on top of plants. This reflector or hood maximises the intensity of light. Therefore, for cloning, seedling and propagation, these are best.  


  • Very low heat, making it very hard for the plant to get burned due to excessive heat; optimal environmental conditions that are required during the initial growth stages. 
  • An estimated 20,000-hour lifespan at the very least. 


  • Not the best option for the flowering stage as the yields may end up smaller than anticipated. 
  • Due to their limited reach, T5s need to be positioned fairly close to the plant, accompanied by a hood or reflector. 

HID – Best for Vegetative and Flowering Phases 

High intensity discharge lights – the kind of lighting you often see in exotic car headlamps. The large bulb generates light through gas ignition within the bulb. In addition to being energy efficient, HIDs provide a lot of intensity. They can be further classified into MH (Metal Halide) lights and HPS (High-pressure Sodium) lights.  

If you are looking for the very best and most optimal lighting conditions for ‘vegging’ your herb, MH grow lights’ high light output fits the bill perfectly. It comes highly recommended for the vegging phase due to the high-strength blue light it emits.  

HPS lights emit yellowish-orangish-reddish beams which are perfect for the flowering phase. However, you should not be limited to choosing either the MH or HPS variety but a combination of both for the most favourable outcomes.  


  • Over the long term, the cost of running HID lights is noticeably less compared to other types of grow lights. 
  • The usable light they produce is more than enough for any grower, and far more than the usual fluorescent lights. 
  • Based on your growing needs, you can reduce the light output as all HIDs are ‘dimmable’.  


  • HIDs produce a lot of heat and can be, in some cases, stressful for the plant. 
  • Using them is not as simple as inserting a plug into a normal wall socket; additional installation tools like a ballast may be required.  

This article has hopefully given you a fair idea of how critical lighting is when cultivating marijuana in an enclosed indoor space. Choose carefully, as certain grow lights may be better suited to individual growth stages.  

Check out our best indoor seeds on our online store.


Cultivation information, and media is given for those of our clients who live in countries where cannabis cultivation is decriminalised or legal, or to those that operate within a licensed model. We encourage all readers to be aware of their local laws and to ensure they do not break them.