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Indoor Marijuana Grow Lighting


Light = Energy

Light is bursting at the seams with energy. Einstein knew it and won a Nobel Prize for it. A fact of nature which gives rise to a plant’s ability to grow, fluorish, and replicate through a process called photosynthesis. This process gives plants the ability to convert light energy into sugars which the plant is then able to utilize for its own needs.

One problem with growing indoors is that a plant can’t get energy from the Sun anymore. This is extremely important to know because without proper lighting, your plants will lack energy. Stalks will stretch in an attempt to find more light and buds will whimper with low weight and potency. By understanding how plants get their energy though, it’s possible to essentially replicate sunlight inside a closet or bedroom and still create substantial end yields.

Big Buds

The easiest way to illustrate how important light is to weed is by imagining how a person would respond in similar circumstances. People obviously get their energy from food, so what happens when a person is starved of food? They become light, thin, and weak. How do you think your buds will react if you deprive them of adequate energy?

On the other hand though, stuff the imaginary mouth of your green beauties with a buffet of light photons and they are going to become plump and juicy. And I love my ladies plump and juicy.

The resources put into your lighting setup will have a huge and direct effect on your overall yields. Do you want tiny fun-sized pebbles of bud or monstrous nuggets of green gold? The light kit you choose will be the biggest factor in determining the answer to that.

Marijuana Vegetative


The Vegetative and Flowering Phases of Growth

There are two separate stages of growth for weed: vegetative and flowering. Which stage the plant is in is determined by the amount of light it receives in a day. If it receives light most of the day, it will stay in the vegetative phase while equal parts day and night will trigger it to flower.

Vegetative (18-24 hours of light/day)

This phase is geared towards building plant structure. This includes developing a healthy root system, a sturdy stalk, and a bustling network of fan leaves.

You can keep a plant in vegetative as long as you want. As long as the marijuana plant stays in vegetative, it will continue to grow in size. Keep in mind not to overgrow your plant as bigger is not necessarily better if the plant becomes unmanageable.

Flowering (12 hours of light/day)

This phase is focused on developing flowers and buds. Plants will grow slightly during this time but most energy will go towards increasing the size and mass of your buds.

Flowering typically takes 8-10 weeks for indicas and 12-14 weeks for sativas. Obviously that will vary depending on strain, but that should be a good rough approximate.

Make sure to prevent as much light as possible from getting to your plant while its flowering and it’s in its 12-hour dark period. Too much light during it’s dark cycle can give the plant mixed signals and severely stunt growth and possibly even cause hermaphroditism.

Light Timing


Setting Up Light Timers

Since the light should be going in regular light/dark cycles (like day and night), using a light timer is a clear choice. Not only does it make sure the light is coming in at repetitive intervals, it also means you don’t have to do any work when it comes to turning them off an on.

Timers are cheap and easy to setup. Usually you will just plug the lighting system into it and then the timer will plug into a wall or surge protector. By moving the dial and pressing a few buttons, your light timing cycle can be working in less than a minute.

Light Types


Lighting Types – CFL, LED, HID

When it comes to growing weed, there are 3 main types of lighting fixtures used. They are compact fluorescent (CFL), light-emitting diodes (LED), and high-intensity discharge (HID). Each type has its own advantages and pitfalls, so make sure you are getting the right light for the job.

CFL Grow Lights

CFL (Compact Fluorescent)

Advantages – CFL’s are the cheapest and don’t take up much space or give off much heat.

Disadvantages – CFL’s give out the least amount of light meaning yields will always be smaller.

LED Grow Lights

LED (Light-Emitting Diodes)

Advantages – LED’s are efficient, give off virtually no heat, and can be maneuverable.

Disadvantages – LED’s tend to be the most expensive and can cost a lot to get decent yields.

HID Grow Lights

HID (High-Intensity Discharge)

Advantages – HID’s are the cream of the crop when it comes to light output. Huge buds incoming.

Disadvantages – HID setups can cost a lot at the start and also run fairly hot.


HID + Reflector – A Light Bombardment

High-intensity discharge setups are definitely what you want to get if yield is your biggest concern. As long as you are able to control the heat and have the space to set the lighting kit up, you are sure to get the best results possible with HID.

Ideally with an HID system, you will also want to use 2 different types of bulbs: Metal Halide (MH) and High Pressure Sodium (HPS). MH provides the optimal colors of light during the vegetative state while HPS works best during flowering. If you have a single bulb system, HPS seems to be what most people tend to use over MH.

Light Reflectors

Your HID system can be further enhanced by having it work in unison with a light reflector. Reflectors greatly magnify the effectiveness of your lights at relatively low cost by redirecting stray light photons and focusing them directly onto your plants. Reflectors can make an HID lighting system 2-4x as effective depending on design and quality at only 20-30% of the cost.


How Light Distance Affects Your Yield

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.

However, they can’t be too close to the light source (especially if it’s HID) or they risk burning. With my lighting setup, I try to get my tops about 12″ from my light. At this range, the max temperature it reaches is about 80 F and maximum light exposure.

  • 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
Light Intensity vs Distance

To help show this, look at the chart above. If we consider 12″ as 100% intensity, then moving it out to 24″ will decrease the light it receives by 75%. In other words, every time the distance is doubled from your plants to the light, the light intensity diminishes to just 25% of its previous strength.

This is why it is so very crucial that you find a delicate balance between light intensity and heat. Make sure your plants are getting their best possible fill of those photons they desire without exposing them to harmful temperatures.


Required Items

  • Light Fixture – CFL, LED, or HID

  • Light Timer

  • Light Reflector (Not Required, but HIGHLY RECOMMENDED)

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