Best lighting for growing cannabis

As you progress in your journey toward becoming a grandmaster grower, you will soon start identifying the limiting factors in achieving those glorious yields we all love to see in photos and videos.

Inarguably, lighting is one of the biggest and most immediately recognisable of such limiting factors. Within reason, the more light you give your plants, the more they will yield.

Other valuable aspects of growing include environmental conditions like CO₂ levels, maximum and minimum day/night temperature, and relative humidity range. Nutrition is also of equal importance. Feeding needs to be adjusted to what the plant is asking for based on its phase in the grow cycle. Some growers even go the extra mile and have classical music or biowaves playing to stimulate the stomata to squeeze in a little extra growth spurt. However, the jury’s out on whether this yields any noticeable results—but it can’t hurt!

Light is, in itself, just another type of “food” for plants. Keeping this in mind will allow you to better decide what is right for you. Just like an athlete has a specific dietary regime for his sport, so must you consider what is the ideal type of light for your growing conditions.

There is little point in blasting your cannabis plants with 2000W/m² if you are just getting started, or deciding on the latest and greatest LED fixture if you cannot dial in the right ambient temperatures. Plant height and spatial limitations also play very important roles depending on which type of lights you decide on.

In this article, we will give you rundown on what constitutes the “best” light for growing cannabis. There are many pros and cons to each, and a little information goes a long way.

A BRIEF HISTORY OF THE GROW LIGHT

In the beginning, there was light…from the sun! Then cannabis became illegal, and someone had the brilliant idea to bring a powerful street lamp indoors to simulate the sun and grow weed.

Not only did this work, but it also created a massive industry catering to indoor/greenhouse operations. This lighting technology is called high-intensity discharge, or HID. Typically, these lights come in one of two varieties, either sodium or metal halide. These lights are very strong, quite inefficient, and produce a substantial amount of heat. But if you manage to tame the heat, they get the job done fantastically well.

Primarily due to space constraints, some growers started experimenting with lower-powered and more efficient lights. More efficient means less electricity is lost to heat, and more of it transformed into actual light. For instance, CFLs—compact fluorescent lights—are quite efficient, small and compact, cheap, and readily found in any common hardware store or supermarket. Ideal for seedlings and clones, they underperform for flowering. This is due to the limited light spectrum they produce. On the other hand, you will be able to fit a few of them inside a covert, desktop PC micro-grow retrofit.

In recent years, we have witnessed the beginning of a new artificial agro-specific lighting era. Modern LED fixtures are superbly efficient, while at the same time producing a great PAR, which means photosynthetic active radiation. This is the measure of the quality and intensity of the light spectrum that the plants actually use for photosynthesis. This in and of itself does not necessarily mean LED is better than HID or CFL—it just means it fills a huge gap really well.

A special mention to plasma fixtures. While operating under the same principles of HIDs, they do have a better spectrum than sodium or metal halide bulbs.

LIGHTS ON, LIGHT OFF

Light schedule is something quite often overlooked. Some growers take years to realise they can further manipulate their plant’s behavior in their favour, with simple light schedule tricks.

The typical schedule will be something like 18 hours on and 6 hours off during the vegetative period, and a flat 12–12 for flowering.

But did you know you can do so much more? You can save significant amounts of electricity if you employ the gas lantern routine during the vegetative period, while maintaining a high level of performance.

Giving your cannabis plants 24 hours of darkness before switching to flowering is known to induce sexing substantially faster in many strains.

During flowering, if you progressively decrease the lights-on period, you will trigger the plant to speed up production. This can be done by setting your timer to turn off 10 minutes earlier each week until harvest. This will simulate the natural shortening of days as autumn sets in while saving you a little extra on electricity.

This technique is sometimes referred to as light deprivation  or the diminishing light technique.

Some growers swear by a 10–10 flowering schedule. The theory is that you will trick the cannabis plant into shorter day cycles. You can fit 8.4 “short days” in each week. That means that a typical 9-week strain (63 days) can be ready in 7.5 weeks (52.3 days).

Even autoflowers can benefit from experimentation, so do not be shy to try it out for yourself.

SAVINGS, SAVINGS, AND EVEN MORE SAVINGS

Even if electricity were free, getting into a habit of saving electricity will not only be an environmentally conscientious thing to do, it will further improve your skills. Understanding and measuring your environment will save you time and money while improving the potential of your plants.

Investing in an automated exhaust system works wonders to save on heating. In the winter, exhaust fans will blow slower, thus conserving heat. Mid-summer, they can work full-power to keep things under control. Many modern inline–exhaust fans come already pre-built with heat sensors for this very purpose.

This can be done cheaper by manually using a quality variac transformer. These will slow your fans down while prolonging their life. Do not confuse variacs with typical dimmers, as these will create a noticeable hum and take a heavy toll on your gear.

If you use butane/propane heaters to warm up your house, slowing down the fans will not only help conserve heat, but will have a dramatic effect on the available CO₂, which will boost production potential considerably. Higher CO₂ levels also mean you can run the grow room at higher temperatures, so it is a win-win situation.

If using LEDs, you can lower the lights closer to the canopy without burning the leaves or buds. You’ll notice you will be using fewer nutrients and water while your girls flourish considerably better.

FINAL CONSIDERATIONS

There are dozens of little tricks to boost yields and save on productions costs. From training, stressing, environmental manipulation, and of course, lighting. But there are no silver bullets.

There is a reason experienced growers swear by one method over another, or one type of light over the next. Even the biggest commercial operations have radically different approaches.

Different genetics, different growing mediums, different growers—this is a never-ending debate. And thankfully so, as it keeps us on our toes and on top of our game in pursuit of top-quality buds.

Remember that what works for one person may be a complete flop for the next. Experiment slowly and gradually introduce the next features—never make rash decisions. This way, you will be able to judge what works and what doesn’t for your operation. Also, be sure to take notes and pictures so you can track your progress.

As you improve and create a deep relationship with your secret garden, you will certainly reap the rewards of the efforts you put into it.