Grow Lights For Marijuana

Tom’s Facts On Artificial Lighting For Marijuana ! 
  1. Introduction – How much Light Do I Want  & Why ?Tube Grow Light
  2. Most Recommended Grow Lights !
  3. Metal Halide Lamps
  4. High Pressure Sodium Lamps 
  5. What Wattage Do I Want ?
  6. What I Use !
  7. What You Need Besides The Bulb !
  8. Fluorescent Lighting ! 
  9. LED Lighting !
  10. CFLs !
  11. Conclusion – Whats Right For You ?

Introduction – How Much Light Do I Want & Why ?

   Grow Lights For Marijuana ! If you are growing organic marijuana indoors then you

Grow Light Fixtures
Air Cooled Hoods

will need some grow lights for marijuana.  All varieties of organic medical marijuana want three things, nutrients, water, and light. Water is pretty much water if it’s PH is within range. Nutrients are already in your soil or you are going to fertilize to get nutrients to your plants. Although the nutrients will affect the size of your plants and flowers (buds) the light your plants receive will have the most dramatic effect on the size and potency of your marijuana buds. The brighter the light, the bigger, the denser, and the more potent your marijuana flowers (buds) will be and you will have more of them.  Proper lighting is extremely important. You will want to use the strongest lights you can afford or at the very least the strongest lights your space and available electricity will allow.

Most Recommended Grow Lights !


Vented Hood
Vented Hoods

Best Lights ! The best lights for growing organic marijuana are few and so we begin with the most recommended lights. The lights that will give you the best results of any grow lights. The best lights are High Intensity Discharge (HID) lights There are two types of HIDs, Metal Halide (MH) grow lights and High Pressure Sodium (HPS) grow lights These lights are the “Gold Standard” for growing organic marijuana.


   Drawbacks ! Although  MH and HPS are the best grow lights and consistently

Centrifuge Exhaust Fan
Exhaust Fan For Lights

produce great yields they have two drawbacks. They use more electricity than most other types of grow lights and they produce more heat than other types of grow lights. If electricity is no problem and your marijuana grow room is properly vented, these grow lights should be your first choice in lighting. These lights should be used with vented light fixtures that makes venting the heat out of your grow room very easy.

Metal Halide Lamps 

 Each of these lamps has its own purpose. The metal halide (MH) lamps produce light that’s best suited for vegetating your marijuana. While the high pressure sodium (HPS) is best suited for flowering your marijuana.

Metal Halide Lamps MH grow lights produces a light spectrum that is more in the

Metal Halide Bulb
Metal Halide Lamps

blue and white range. The metal halide bulb gives off light in the blue spectrum, making it perfect for vegetating organic marijuana because it simulates the natural sun’s light for the spring and summer. This blue spectrum light gives young growing organic marijuana plants exactly what they want and need. Vegetating marijuana plants when exposed to this blue spectrum light will explode with fast vegetative growth while keeping your plants compact and bushy. Metal halide lamps are my choice for vegetating and growing organic marijuana. I have used MH lamps for an entire seasons grow from beginning until harvest and the finished buds were fantastic. I do however agree with professional and serious hobby growers that HPS lamps are a better choice for flowering your organic marijuana.

High Pressure Sodium Lamps

HPS grow lights emit a red , orange, and yellow

HPS Bulb
High Pressure Sodium Lamps

spectrum which simulates the natural sunlight of fall and winter, when marijuana naturally flowers. When you decide to flower your organic marijuana you will want to change your metal halide (MH) bulb to a high pressure sodium (HPS) bulb. Using a HPS lamp for flowering, allows your plants to take advantage of the ideal light spectrum that’s emitted from the HPS bulb.

If You Must Choose Only One ! HPS grow lights are not usually used for vegetating plants because they cause young marijuana plants to stretch tall, where as MH grow lights produce compact tight plants. This is the reason I recommend using MH grow lights for the entire grow, only if you insist on using only one type of grow light, and because of my experience using MH grow lights.

What Wattage Do I Want ?

   What Watt ? 125 and 250 watt high intensity discharge (HID) lamps are available for

Hood & Ballast
Hood & Ballast

growing. I would not use them. Why,because they are not efficient and you can obtain better results using LEDs or a T – 5 fluorescent light, while using less electricity. Many growers get great results using a 400 watt HID for 4 to 6 plants and a 600 watt HID for 6 to 12 plants. I have seen excellent medical marijuana come from 400 watt and 600 watt grows that I didn’t think was possible. A 1000 watt HID grow light is excellent for a large space but they radiate a lot of heat that you must deal with, making them unsuitable for a small space.

   What I Use !

I use two 1000 watt MH grow lights (open fixtures) in my marijuana vegetating room,

Tube Lights On

with 9 plants under one light and my mother plants under the other light. I use three 1000 watt HPS grow lights ( vented tube light fixtures) in my marijuana flowering room for 18 plants. I use this wattage because I have a relatively large space. The space isn’t as large as the dispensary grow where I work. There I have thirty MH grow lights in the vegetating room, with 9 to 20 plants under a light, depending on their size. In the dispensaries flowering room there are 30 HPS grow lights with 9 plants under a light. My recommendation is to always use the brightest light (highest wattage)your space can utilize.

What You Need Besides The Bulb !

   You Need More Than Just A Grow Bulb ? High intensity discharge (HID) light bulbs need a special light fixture. HID bulbs can not be screwed into just any light fixture. All high intensity discharge lights whether they are metal halide (MH) lights or high pressure sodium (HPS) lights, require  three items.

  1. The light bulb ! Wattage of your choice.
  2. A HID Ballast !This must match the wattage of your HID light bulb .
  3. A HID light fixture ! This is usually an air-cooled reflective hood .

    Maginetic Ballast
    Magnetic Ballast

The Ballast !The HID ballast is matched to the HID grow light bulbs wattage and is used to control the flow of electricity to the  grow bulb. This is why the HID bulbs can’t be screwed into a regular light socket. There are two types of ballasts you may choose from, a magnetic ballast or a digital ballast. Both of these usually have switchable voltage from 120 to 220 volts so you may

Digital Ballast
Digital Ballast

use either one. The magnetic ballast is usually less expensive, but produces more heat, makes a little more noise(buzzing sound) and is less efficient than the digital ballast. The digital ballast is more efficient, makes less noise, is a little smaller (takes up less space than the magnetic ballast) but is more efficient. Both of these work very well and I use both.

Open Fixture
Open Fixture


   HID Light Fixture ! Light fixtures for metal halide and high pressure sodium (also known as “sodium vapor”) bulbs come in two basic styles. One is an “open style” light that is basically a HID light socket with a high polished aluminum reflector. These fixtures are very open and best used in very large grows with high ceilings. The high ceilings permits the heat generated from these lights to rise above the

Open Light
Open Fixture

plants and then exhausted out of the grow room. These open fixtures are the least expensive. The second style is a closed or air-cooled fixture. These come in two basic styles known as hoods or tubes.  The hoods and tubes are enclosed with a vent on opposite sides of the fixture to vent air in one side and out the other. To accomplish this , an exhaust fan is installed outside of the grow room. flexible ducting is attached to one side of the hood

Air Cooled Tube
Air Cool Tube

or tube with the ducting continuing to the exhaust fan outside of the grow room. When the exhaust fan is turned on air is pulled through the hood or tube , past the HID bulb, and exhausting the heat out of the room. This is an efficient way to keep your room cooler  and your lights can be kept much closer to your plants. The closer the light to your plants the denser your flowers (buds) and the more compact your growing organic marijuana will be.

Fluorescent Lighting ! 

Traditional fluorescent light bulbs are called T8 and T12s. Who knew that? Although you can grow plants under traditional fluorescent lights , they are best used for plants that like to grow in the shade. Marijuana doesn’t want to be in the shade so these lights are not a good choice for growing organic marijuana through the vegetating and flowering stage. However, traditional fluorescents are good for rooting freshly cut clones of marijuana. New clones (cuttings ready to root) want shade so they can concentrate on producing roots. This is the only use traditional fluorescent lights have in a marijuana grow room setting, other than lighting your work area.

T5 Fluorescent Lights ! T5-HO (high output)  grow lights are powerful (for a T5 fixture 8fluorescent light), quiet, cool operating, efficient (uses less electricity per watt) than other grow lights. T5-HO lights come in many configurations. T5s come in two foot or four-foot lengths. They also come with your choice of 1 bulb, 2 bulb, 4 bulb, 6 bulb, or 8 bulb fixtures. This makes them very versatile for different sizes of growing applications. T5s being a cooler operating light makes them a good choice for hot areas around the country, since they require less ventilation and cooling fans. Since T5s are a cool operating light they can be used as close as a couple of inches away from your plants for better light penetration without burning your plants. The closer your lights are to your plants means, nice tight compact plants, perfect for indoor growing applications. T5-HOs also uses different bulbs for vegetating and flowering marijuana. For vegetating 6500K bulbs are available. For flowering you willT5 grow lights with plants want to use the bloom 3000K bulbs. If you like you can even mix the bulbs for a balanced 5400k light. There is now also a UV-A Plus bulb for final flowering. I use a T5-H0 eight bulb, four footer to grow my 6″ potted plants until they are ready to be re-potted into larger pots. I also use a four-foot two bulb T5 for my newly rooting clones. T5-H0 produced light will only penetrate well to about two feet, which makes them perfect for small plants no more than 24″ tall. This is the reason I only use T5s for small plants and go with HIDs for larger plants.

Led Lighting !

Light – Emitting Diodes (LEDs)  for growing plants indoors is relatively new LEDsalthough the technology is maturing and getting better all the time. This is why some folks report good results and others say they are almost worthless. As with a lot of new technology there are some LEDs that work well and others that will not perform as well. It can be almost impossible to tell which ones are good without trying the different models. Unfortunately LEDs can be very expensive which is their main drawback, making trying different models difficult to do. LEDs are becoming more mainstream because they do have a lot of advantages over traditional grow lights and because these lights emit veryLEDs specific wavelengths along the electromagnetic spectrum. Since LEDs emit these specific wavelengths it means they are not wasting their energy on light that isn’t usable to plants as with traditional grow lights. This is the reason LEDs are very efficient electricity users. LEDs can be plugged into any regular electrical outlet and do not need a ballast. LEDs emit very little heat adding to their usefulness for small spaces and hot areas around the country. Since LEDs run cooler than typical grow lights they can be within inches of your plants without scorching them. Being cooler and not emitting heat makes ventilating hot air out of the grow room unnecessary. LEDs also have a long lifespan another good reason to use these lights. High pressure sodium (HPS) light bulbs have a life span of about 3,000 to 5,000 hours or about one year. On the other hand LEDs lifespan is around 50,000 to 100,000 hours or about seventeen years. That’s a huge difference. Although LEDs are very expensive, what you save in electricity, ventilation, and new bulbs, may make their expense worth it. If you use LEDs keep inLED lights mind that they are stage specific. What I mean by this is, blue LEDs are for the vegetating stage of growing while the red LEDs are for the flowering stage of marijuana. You can incorporate both the red and blue together and use this combination throughout the plant’s life. If you are looking for a way to beat the heat, without using some type of air conditioning, and want a grow light with a low consumption of energy, then LED grow lights may be the best choice for you.

CFLs !

Compact fluorescent Lights (CFL) are your everyday household light bulb, that can CFLbe purchased in any, hardware, grocery, home improvement, or big box store. Yes , you can grow plants under these. Unfortunately they are no different from regular fluorescent lights other than being compact and fitting in a regular light socket. These do not provide enough light except for clones that are trying to root. I don’t recommend these lights for anything other than clones as I am sure you will be disappointed with the results if used for an entire grow and flowering cycle. If you are serious about growing organic marijuana these lights are not for you. However, if you just want to play with growing organic marijuana they may be ok !  I do not recommend these grow lights for marijuana.

Conclusion – What’s Right For You ?

Heat, Space & Electricity !  There are three main considerations when deciding  on grow Dispensary Marijuana Growlights for marijuana. How large is your growing space ? How will you and can you deal with heat ? Is the available electricity enough for what you want ? Most growers will tell you to go with the brightest grow light that you can. If heat is going to be a problem and you want to use HID lights, a vented hood will be needed. If you don’t want to use a vented hood for your lights then LEDs may be a good fit for you. If heat isn’t going to be a problem and your ceiling is high enough than an open fixture should be OK.

Higher Watt – Higher Yield ! I recommend you use the highest wattage that you are able too. The brighter your lights, the denser your flower buds will be with the most THC, along with a higher yield. t5 light

Fluorescent Grow Lights are best used for clones, seedlings, and plants in 4 to 6 inch pots. They may also be a good choice for a mother plant. I do not recommend fluorescent grow lights for any plants in a pot larger than 6 inches and would never use them for flowering marijuana.

CFLs , may be ok for clones and seedlings but are not the best choice. It is my opinion that CFL’s are worthless and should not even be a consideration when growing organic marijuana. CFLs are definitely not for the serious grower.

The Best Grow Lights for Marijuana are the High Intensity Discharge lights. The MetalBasement Grow Room with open grow light fixture Halide and Sodium Vapor grow lights that are 1000 watts remain the gold standard of growing organic marijuana. LED’s are catching up fast as the technology of these lights is growing every day. When it comes to growing organic marijuana my first pick for grow lights are the HID 1000 watt lights if you are able to control heat. If heat is a problem then I would go with LEDs.

Go to Page : Grow Room Setup ! ,  Page : Vegetating Marijuana !

Author: Tom D.



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