UNDERSTANDING THE BASICS OF INDOOR HORTICULTURE LIGHTING

BY ADAM JACQUES

Lighting is right up there with nutrients on the scale of diversity and personal preference in a grower’s indoor garden. There are so many arguments revolving around this topic, that it can make a person’s head spin when trying to decide what will work best for them. After the decision is made as to what style lights are going to be used, the even more daunting task of choosing a brand comes in to play. There are practically as many options as there are strains and It can all be a little overwhelming to the novice indoor grower.

Phases of plant growth play a large part as to what kind of lights to use. Plants in the garden cycle through different lighting before reaching their end stages of growth. Understanding what it is a plant needs at those stages, as well as what is most economical to the grower is key in buying and rolling out a lighting plan in your space. A typical traditional grow room set up will use T5’s florescent for the seedling and cloning phase, a MH bulb for vegetative growth before bloom, and an HPS for the blooming phase of the plants. These bulbs will mimic fairly well the spectrum of light cannabis plants need during those phases. The idea is to recreate the sun and it’s cycles as closely as possible in your space. Varying genetics have different lighting requirements based on their natural geography, so plan accordingly. Doing your research and looking at the short term, versus long term value of your lighting plan is important. A good rule of thumb is to over plan and under spend. You can always add more gear later if needed.

Next we will delve a little deeper into lighting hood types. The type of hood that you pick for your lights will directly effect the output of your grow in many ways. The most basic and common type of hood for lighting will be your basic bat wing reflector. The light broadcast to your plants will not be diffused by glass like on an enclosed air cooled hood, but the amount of heat created will be great. Bat wings are fine for smaller grows with a good exchange of air and ample AC.

The next step up will be air cooled hoods. Air cooled hoods come in both sealed and open varieties. The lights will have open ports on each end to attach ducting that is attached to large fans. The fans move air over the bulbs and extract the heat out of the room. The best of these are enclosed with glass which seals the entire housing. While as stated before, the glass will block some of the available lighting spectrum, it has many bonuses that will increase the effectiveness of your grow. With an enclosed hood, adding Co2 to your room will be easier as the fans will not be pulling your Co2 out of the space. Also, as kind of a bonus, the ducting can be run to other portions of your house to supplement heating, as the hot air would be wasted otherwise if vented outdoors. The most common lights used in home grows and smaller medical grows are the 1000w bulbs sealed in an enclosed housing.

There are many other types of hoods available. The common thread connecting them all is the interior aluminum or mirror because it offers 95% reflectivity, is long-lasting, and easy to clean. It is important to keep your reflectors clean and free of dust as this will hurt the percentage of useable light that will make it to the plants. Make sure that your hoods are set in such a way that there are no direct hot spots. We want the light emitted to fall equally amongst the plants. A good rule of thumb is that most commercial grow lights will cover a space of 16 square feet. If you do not have 4 feet of space in either direction you will likely lose some light to walls causing inefficiency in your grow.

When looking at hoods and lighting the old adage stays true, “If it sounds to good to be true then it probably is”.
Another key thing to think about when lighting a room is room temperature and climate control. Every light you add will increase the heat within your space. Rule of thumb is that for each 1000 watts of lighting you are using you need to add 4000 BTU of air conditioning. Most grow lights will give off a similar amount of heat watt for watt. This can of course be mitigated with heat sinks, air cooled hoods, sealed hoods, liquid cooled hoods, and air flow. Within a small grow you can likely get away with an air cooled system and very little AC. As we grow into larger spaces utilizing double ended bulbs and no air cooling on the light, our cooling needs grow dramatically. There are many resources and calculators online that can help you figure out your space and give you an estimate of required AC usage based on wattage used. These BTU approximations are recommendations under extreme conditions. Pairing an air conditioner with an indoor grow room is not always as simple as one might think so plan accordingly. Also factors like in room dehumidifiers, magnetic or digital ballasts, pumps and other equipment may cause additional heat concerns. It is important to always remember that more light will always equal more heat.

The question that most people ask at this point is “Well which lighting system is best for expected harvest?”. That is a question that can be answered in a numerous ways by a multitude of people. It really matters who you are talking to, what their experience has been, and if they are trying to sell you something. Personally I am of two schools of thought on the matter. The most efficient method of growing in flower will utilize HPS bulbs. The amount of useable light created for the electricity used is the most efficient way to increase yields in your garden.

When it comes to potency the highest terpene and cannabinoids counts that I have seen have come from use of LED or Plasma options. So do you have to choose one or the other? No. You can run HPS solutions and supplement with LED or Plasma or even Ceramic Metal Halide. With the combination of technologies you can closely mimic the Autumn sun which is what we have intended to do all along. There is a limit to the usable light of cannabis plants though, around 100 watts per square foot, so plan your footprint accordingly. All of this information may seem a bit overwhelming.

Doing research online is paramount. Technology is changing every day. Understanding where the technologies are and where they will be shortly is extremely important to optimizing your grow at the lowest cost to you. Lighting is one of the very important keys to optimizing your indoor grow. Take your time, understand your options and make the decision that will best fit your individual needs.

There are so many resources available to starting growers when it comes to lighting. Any company who sells lights will be available to give you handouts and advice. Customer service at your local grow store can help you make informed decisions. Online forums and blogs can give you hands on information about the currently available products.

Knowledge is power and lights use a lot of power.

Make sure to harness it.

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