Lights, lights, and more lights!

Ok, time to finally do an article on lighting for your indoor plants. The arguments in this category are huge, and there are many different variations that people use. There are different spectrums of light emmitted by light bulbs, measured in Kelvin. Plants can mainly utilize the blue(upper levels of kelvin, around 6500K) durring vegetative growth, and red(lower levels of kelvin, around 2700k). Yellow and green light is of little use to them. Another measurement is Lumens, which is the amount of light produced by a bulb.


CFL's (Compact Fluorescent Bulbs)

CFL's have become more and more popular lately for their ease of use, price, power draw, long lasting bulbs, and low heat emission. CFL's produce about 65 lumens per watt. My personal recommendation is to have 6000 lumens of 6500k lights, and 3000 lumens of 2700k lights per square foot of grow space. Keep the CFL's preferably about 1-2 inches above your plants. One more note about CFL's is that they are incredibly easy to obtain, and at a low price.


HPS (High Pressure Sodium)

HPS lights are hotter, more expensive, pull more power(because of their size), and are harder to come by than CFL's. The up sides are that its the more traditional method for growing marijuana plants indoors, and many people feel that it makes the plant produce more bud. Of course there are doubters to this part of the theory. High pressure sodium lights emit mostly orange, yellow, and red spectrum light, which is perfect for the flowering stage of the plants growth. If you choose not to use CFL's, and can't afford both an HPS and MH, then just get the HPS. Just make sure you can properly cool these two types of bulbs.


MH (Metal Halide)

The MH lights emit a lot of the blue spectrum which the plant likes for root, stem and leaf growth. MH is part of the High-intensity-discharge (HID) family of lamps, produce high light output for their size, making them a compact, powerful, and efficient light source. Similar to HPS, these bulbs are on the expensive side and harder to find. They run fairly hot and need good air flow to remove the heat from your setup. These are more traditional and famed for great veg groth.


Approximate light production:
Fluorescents: 60-70 lumens/watt
Metal halide: 90 lumens/watt
High pressure sodium: 107 lumens/watt




These are the 3 top types of lights used for growing, there are others, including the newer LED grow setups.



I prefer CFL's for relatively smaller grows, and for larger grows I prefer MH for vegetative growth, and HPS for Flowering.