Which are the best lights to grow Cannabis?

Posted 7 years ago by Ian Shutts

The debate over which are the best lights to grow cannabis has been going on since the inception of indoor growing. Recently it became the storm of forum debating since the new generation of horticultural lighting hit the market just a few years ago.

The best light will always be the light that best fits your needs. If you are a PC micro-grower, you will not want to put a 250w HPS light in there! You will fry your plants. On the contrary, do not expect a 450g/m2 yield out of a 250w CFL.

Newer technologies have emerged, and as you might expect, purist veterans will frown upon the latest greatest thing. In their defense, they are guardians against false marketing claims and exaggerations. But as years went by and growers started experimenting with newer light technologies and showing practical results, the evidence has become unquestionable.

We will not make a judgment on what is best for you. We will explore the options out there and give a brief overview of their Pro’s and Con’s – fact is if used correctly any grow light will make plants grow healthy and green.

Traditionally, for both greenhouse and indoor growing, you would have a choice of just two technologies. CFL and HID. The newer proven technologies are LED and Plasma.

CFL, which stands for compact fluorescent, is your regular modern household lighting. These are very cheap and require no particular setup. You will find these in wattage intensities ranging from 5w to 250w. There are a few horticultural specific lights with a targeted light spectrum for either vegetative of flowering, but for flowering, these are not the most productive lights. On the other hand, they are fantastic for cloning and early veg. They produce very little heat, which is a huge plus for small confined spaced with modest airflow. To this day, the CFL T5 is the undisputed king for propagation and micro-growing. They produce no sound and will not burn your skin off if you accidentally touch it.

HID – stands for High-Intensity Discharge. This is historically the most used light of all times for growing pot. Partly because it was the first light used indoors that was able to produce results comparable to that of growing outdoors. Quite literally, these were street lamps that were repurposed for growing weed indoors. They come in two main varieties, MH (Metal Halide) and HPS (High-Pressure Sodium). Metal Halide has a bluer spectrum, which is favored for the vegetative phase. High-Pressure Sodium has more power on the near red spectrum, which is ideal for flowering. HID lights require a ballast to operate, which can be a bit tricky and risky with older electrical setups. The ballast also emits elevated quantities of RFI frequencies, which puzzles pH meters that might be close by. It also produces a significant amount of heat, which can be either a good thing or a bad thing depending on where you live but is usually a problem in the summer regardless. You will find these between the 250w and the 1000w power rating. These are the lowest concerning price per watt, but a bulb will last you for 3 or 4 crops before it needs replacing. They are extremely dangerous in they can cause severe damage if they are accidentally touched while hot. A simple splash of water can make them explode. But, with proper precaution and a bit of sense and sensibility, they are as dangerous as your old incandescent lights at home.

Plasma lights – Plasma lights have a rated operational lifetime of around 30,000 to 50,000 hours. They are full spectrum, so they mimic the sun’s PAR (photosynthetically active radiation), but with added useless band waves, light green and far reds. The benefit of this is that this light is equally useful for both vegetative and bloom phases. It produces less heat, as more of the electricity is converted into actual light. They are the most expensive lights to buy. They are very expensive, but the best brands do offer extended warranty and servicing deals. They have a quiet operation and are relatively easy to service. They produce fantastic results per rated watt, but the upfront cost has not given them much traction in the real world. Maybe as production costs decrease, we may see more of these out in the wild.

LED – Light Emitting Diodes. These are the rage right now. After the first couple of years of bad reputation, horticultural grade LED became the top choice for growers around the world. They are getting cheaper and cheaper every year and easily compete with HID in terms of production and price. Upfront, the cost will be a bit higher per watt, but due to their +50,000 hours of operating lifetime, they will come out significantly cheaper in the long run. They are usually built with cooling fans, which make them a little noisier than other solutions, but you can already see top brands offering completely silent units. You can find LED grow lights in numerous configurations and wattages. From 5w to 1000w, and everything in between. You can very easily order one with a light spectrum to your specification, but generally, they will have a good blend of both reds and blues making them ideal for both vegetative and flowering phases. There are even some brands that have smartphone apps so you can dial in specifically which light spectrum recipe you wish to give your plants at each stage of growth. They produce the least amount of waste heat, second only to CFL. The only thing to look out for is for dodgy manufacturers. The vast majority are white label manufacturers from China, so the market is quite flooded with second rate products. Nevertheless, they are safer to operate than HID. If you decide on LED, do not go for cheap eBay deals. Find a reputable vendor with solid warranty offer.

There you go. In a nutshell, all about growing lights. The seasoned home grower in the temperate regions of the world is likely to have a mix of these lights. He may use CFL for cloning and seedling and choose LED to veg them out. In the winter he may use HID and save money on heating, while in the peak of summer just stick to LED as they run at ambient temperature. Some growers even take it a step further, for example swapping and High-Pressure Sodium bulbs for a Metal Halide in the last weeks of flowering. Why – you may ask? Because the Metal Halide bulb also emits a good amount of UV light spectrum, which stresses the plant to turbo charge resin production to defend itself. Others may use Metal Halide all the way to help tame a sativa’s stretchiness. Light is just another tool in the grower’s bag of tricks. Learn to use them wisely, and you will certainly get out what you put in.