Grow Lights


Light is Food for Plants

Lighting is a fundamental component when creating an indoor grow room. Understanding a little bit of the science behind light and its role in plant growth underlines the importance of efficient, effective lighting.

The key process that provides marijuana with their sustenance is called photosynthesis. This is the process used by plants to convert light energy into sugars which the plant is able to utilize for its own energy needs.

Compare this to how people operate. We eat for 2 reasons: nutrients and calories (energy). Hydroponics systems provide the plants nutrients through the water solution, but that is not where the plants get their energy from. They receive all their energy from the light source you set up for them.

Imagine a person who gets all the vitamins and essential nutrients for their body to operate efficiently, but they have no calorie intake. They would be skin and bones. On the other hand, if a person consumes a wealth of calories, they can achieve a healthy weight or even become massively overweight.

Buds this juicy require an abundance of light.

When it comes to lighting for your plants, the question you are really asking yourself is “Do I want skinny buds or fat buds?” The amount of light you offer to your plants will be the answer to that question.

For reference, my lighting setup represents 70% of the cost of my total system. That’s how important it is.

Marijuana in the Vegetative Stage

Marijuana in the Flowering Stage

The 2 Stages of Growth

Marijuana plants have 2 different growing phases: vegetative and flowering.

  • Vegetative – This phase is geared towards building plant structure. This includes developing a healthy root system, a sturdy stalk, and a network of fan leaves. Light should be exposed to the plants 18-24 hours a day during this phase.
  • Flowering – This phase focuses on flower/bud development. Marijuana plants automatically switch from vegetative into flowering when they get less daily light. Many growers use a 12 hour light/dark cycle, but some choose slight variations of that.


Light Timing

Because you are growing indoors, your mission is to simulate what occurs in nature with light which basically means creating day and night cycles. Since these cycles should happen in regular intervals, the best way to manage lighting is by using a timing device which automatically turns the lights on or off for you.

A timing device is a simple, cost-effective way that makes sure your plants always get the exact hours of light that you want them to get. It also means you don’t have to switch the lighting off and on yourself every single day which is an unnecessary hassle and risk if you miss turning it on or off at the right time.


Types of Lights

To compare different types of lighting, you need a way to compare different lights in a universal way. Comparing lighting is done by looking at the unit of measure called lumens (if a light doesn’t specify lumen output, I would ignore that particular light).

Simply put, the more lumens a light can produce, the more light (food) that your plants will receive. If one type of light outputs 5 times as many lumens as another, you can expect that your plant would have access to roughly 5 times the energy. This could likely lead to 5 times the end yield as well.

There are 3 different kinds of lighting to consider: Fluorescent, High Intensity Discharge (HID), and Light Emitting Diodes (LED) each with their own pros and cons.

    Example of Fluorescent Light Fixture

  • Fluorescent – These bulbs are the least costly types of lights, but not surprisingly they are also the least effective. They are fairly efficient, but they don’t have the same kind of wattage behind them as an HID which makes a big difference. They also don’t give off heat which means you can put them within inches of your plants without burning them.
  • Example of HID setup

  • HID –These are the most expensive of the bunch, but they are the choice of any serious growing enthusiast. If you plan on really digging deep into growing, an investment into HID is probably the best choice you can make. It will give amazing returns in the form of huge potent bud yields. There are 2 types of HID lamps used for growing marijuana indoors: Metal Halide (MH) and High Pressure Sodium (HPS).
    • MH – Emits a blue light which is ideal for vegetative growth. MH lamps tend to do a good job of preventing plants from stretching, which means they will stay more compact. This is especially useful for smaller growing rooms.
    • HPS – Emits an orange/red light which is ideal for flowering. They also tend to be slightly more efficient than MH bulbs by producing less heat and more light.
  • I Got My HID Lighting from Stealth Hydro. Never Had to Replace Anything in 2 Years of Use!

    Another important thing to know about HID lighting is that it requires the use of a ballast. A ballast is a device that limits the amount of current that can travel through the lighting system thus saving it from damage.

    If cost is a major concern, it is possible to purchase just an HPS bulb rather than both and still get positive results. Yields won’t be as optimum as they were if you are able to use MH in vegetative as well, but it will surely be better than a fluorescent or LED setup.

    Example of LED Fixture

  • LED – This form of lighting tends to be in between fluorescent and HID in price, and in effectiveness. One advantage of LED lighting is that they don’t take up much space and are relatively maneuverable. If space is a serious issue, LED might be a great solution. The biggest drawback is going to be its light output when compared to HID.


Light Distance

The distance at which your plants are away from the light source is very important to consider. As common sense would suggest, the closer your plants are to the light source, the more energy that will be available to them.

On the other hand, if you are using an HID system, the light source will also generate a lot of heat. Putting your plants too close to the light could end up deterring growth or even burning them. I find that a safe distance is having the tops of your plants 12” away without proper air circulation or 6“ if your system blows the hot air out of the system and away from the light. I haven’t been able to try with the proper air circulation, so 6” is just an estimate.

One other thing to know is that light strength is inverse to distance and not linear. This is best explained with the table below which shows distance and relative light strength. For this example, I consider 12” to be the optimum distance giving 100% light output.


  • Plant distance = 12” – 100% light
  • Plant distance = 24” – 25% light
  • Plant distance = 36” – 11% light
  • Plant distance = 48” – 6% light
  • Plant distance = 60” – 4% light

Graph Showing Effect of Distance on Light Intensity

You can see from the table that if your plants are 24” out, they are only getting 25% of the light output when compared to 12”. One might expect that if the plants went from 12” to 24” that since distance is doubled, available light energy would be cut in half. However, it is actually cut into a quarter. This helps illustrate the point that you want to get your plants as close as you absolutely can to the light without exposing it to extreme temperatures.

Hanging your lights by chains is a great way to give you the ability to adjust as your plants grow.

My Reflector Setup with HPS Bulb Installed.


When light is emitted, it travels in all directions away from the source. Light reflectors work in conjunction with your lighting system by redirecting the light that travels in a useless direction (towards the ceiling) and reflecting it towards where you do want it to go (your plant’s outstretched leaves).

Reflectors greatly magnify the effectiveness of your lights at relatively low cost, and they never need to be replaced. I haven’t been able to find any exact results, but I would say reflectors make an HID lighting system 2-4x as effective depending on design and quality.

Reflectors are optional when it comes to lighting, but if you can afford to buy one, you definitely will be rewarded in your end yields. If you don’t get a reflector, using a room with white walls is highly suggested.

Light is Your Plant’s Most Important Resource. Go Big and You Will Reap Great Rewards!

Action Steps

  • Determine which consideration is most important for you in your lighting. These are the recommendations I would make.
    • Cost – If budget is an issue, buy fluorescent
    • Quality – If quality is what matters, buy HID
    • Space – If you have limited grow room, buy LED
  • Once you know what lighting system you want to go with, plan out where you can put it. You need a space where you can set up a lighting system AND keep light out effectively for the flowering stage.
  • Get your lighting system today and set it up as soon as possible. If you want to start being self-reliant for your marijuana needs and stop paying ridiculous premiums to your weed provider, start taking action now!


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