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Grow Light Guide

LIGHT HOURS FOR Marijuana VEGETATIVE GROWTH = 18 hours per day
LIGHT HOURS FOR Marijuana FLOWER GROWTH = 12 hours per day

What lights do you need to grow marijuana weed plants?
Grow marijuana weed with the following lights, they are in order of best to last:

1. High Pressure Sodium Lights complete with Ballast (HPS power supply) These lights are in the Red Spectrum of light. Their Kelvin rating is about 2700K which is the best for flowering buds. These HPS grow lights are great in both Vegetative and Flowering stages. There are 3 main parts to High Pressure Sodium lights: The BULB, The Ballast Power Supply, and the Reflector. The same goes for High Power LED and Metal Halide. They consist of the same 3 parts. A good example of these lights are FLOOD LIGHTS. Flood lights can be purchased at Home Depot and Lowes in Metal Halide and High Pressure Sodium. They come with the bulb, ballast and reflector with housing. These are not recommended however because of the design. Hydroponic versions of HPS and MH are much lighter in weight and are designed to be cooled with air. They are optimized for growing with plants. Home Depot and Lowes flood lights do work, so if its all you have use it.

2. Metal Halide Lights complete with Ballast. (MH) These lights are in the Blue Spectrum of light. Their Kelvin rating is about 6500K which is the best for vegetative stage growth. These are great to use the entire growth but must be accompanied by HPS during the Flowering stage. HPS is a must have during the flowering stage. I do recommend both spectrums the entire growth with emphasis on HPS for flower. Did that make sense? (not sure it did)

3. Compact Fluorescent Lights. (CFL) These lights are in both Blue and Red light spectrums. These are great grow lights for small cramped places. They produce a good amount of light and have a broad range in Kelvin. They come in 2700k 4500k 5000k 6500k. CFL grow lights produce little heat and do not need cooling in low wattages. If you simply cannot use HID (high intensity discharge) MH and HPS, CFL or LED are a great option. Although CFL grow lights do work do not expect a large harvest. CFL can and does produce bud, but no where near HID lights.

5. HIGH POWER LED MULTICHIPS. There are great lights to grow with. When using these high power led grow lights make sure to use the correct spectrum. Stay with 2700k, 4500k and 6500k spectrums. I recommend you grow with both spectrums 2700k and 6500k the entire growth. HIGH POWER LED can be easily custom built which is just awesome. I will be selling 2700k and 6500k in one LED light soon.

4. The following lights should not be used for growing plants:

Low Power LED- These low power led are the generic blue, pink, white and purple led lights flooding the market. Beware and do not buy these worthless grow lights. When buying LED make sure its HIGH POWER LED of 10 watts or more per bulb.

Mercury Vapor- These mercury vapor lights are energy wasters. Walmart sells a mercury vapor flood light that should be avoided.

Halogen- These lights are beyond energy wasters. They produce a vast amount of heat and less light! I find it hard to believe there is a market for these.

Incandescent lighting- Very low power and not for plants! I love the incandescent light bulb, but not for growing!

Low Power LED lights are overpriced and underperformers.

NOTE: The newer high power led multichips are good for growing however. The bad LED lights are the ugly, blue, pink and solid red ones. When using LED make sure they are 2700k 4500k and 6500k spectrum NOT BLUE, RED or PINK etc.

How many hours of light to grow marijuana plants? What are the Light hours for growing?
For your first week of vegetative growth start off with: 18 hour days and 6 hour nights.
These hours make the plant grow in the "Vegetative Stage". You can stay on 18 hour days and 6 hour nights for 1-8 weeks. Then you must switch to the "Flowering Stage" to force the plants to start growing flowers. (BUDS)
For your plants to start growing Buds change the light hours to: 12 hour days and 12 hour nights.
These hours make the plant think it needs to flower. This is when you start to see buds forming. It takes between 6-12 weeks to finish budding.

What wattage do lights come in?
Common High Pressure Sodium (HPS) and Metal Halide (MH) bulb wattage: 70, 100, 150, 250, 400, 600, 1000
Common Compact Fluorescent (CFL) wattage: 23, 45, 65, 80, 100, 150, 200
Higher watt usage means more buds and higher electricity.
Lower watt usage means less buds but save electricity.

What's the best kelvin rating grow light for marijuana vegetative growth?
6500K metal halide is great and recommended for vegetative growth. Just in case you can't get or dont't have 6500K, 2700K color also works for growing vegetative plants especially HPS lights.

What's the best kelvin rating grow light for marijuana flower growth?
2700K is the best choice for flowers in budding. High Pressure Sodium HPS lights are the most powerful choice and the flowers thrive in the reddish orange light giving you bigger heavier buds.

How many marijuana weed plants can I grow per square foot?
I would say about 4-6 large plants in 3 gallon pots for every 4 square feet. You can grow more plants in smaller pots if you like.


high pressure sodium grow light bulb

HPS above, MH below

metal halide mh light bulb

CFL Light Bulb

cfl 23 watt grow light bulb