Growing indoors offers many benefits, but with them come many challenges. The main problem with growing plants indoors, is the availability of light.
The vast majority of grow rooms will not have sufficient natural lighting to grow strong, healthy plants with maximum yields. The solution to this is simple, artificial lighting.
Artificial lighting comes in many forms, and many sizes and intensities depending on what is needed for that particular space.
How is light measured?
Temperature does not refer to the actual physical temperature, but rather is a way of describing the spectrum of light emitted. The most common measurement of this is listed in Kelvins.
This scale ranges from around 1000K to 26000 K. The higher the number, the more blue/white the light emitted is. This lighting tells plants to grow upwards and develop thicker shoots, more leaves, and stronger roots. Lower kelvin spectrums are much redder in color, and signals many plants to begin flowering and preparing for winter.
Choosing the best spectrum of lights for your plants is just as important as providing enough intensity. Grow lights can be tailored to fit each stage of plant development, whether propagating, vegetative, or flowering. Grow specific lights are also designed to supply plants with enough of the RIGHT spectrum to create energy efficiently as well.
Daylight = ~4600 K
Warm CFL = ~3500 K
Cool CFL = ~6500 K
MH = ~5000 K
HPS = ~3000 K
Sunrise/sunset = ~1500 K
Light intensity is most commonly measured in lumens. Lumens refer to the amount of light emitted per second from a light source.
Lumens are not the best way of measuring the quality of a light source however, and is only one factor in what makes a light high quality, or useful for indoor cultivation.
Fluorescent bulbs (CFL) generally fall somewhere between 3500 K and 6500 K. CFL lights intended for propagation or growing usually fall somewhere around the top end of this spectrum. This is seen by the human eye as a white or light blue colored light and resembles that of daylight very closely. Fluorescents emit very little lumens however, and need to be placed fairly close to your plants in order to deliver enough energy to maximize growth.
LED lights come in a wide range of colors and spectrums and in fact can be tailored to nearly any spectrum. This makes LEDs a popular choice for those wishing to maximize their crops while emitting very little wasted energy in the form of heat. Some LEDs even let you choose the spectrum of light emitted by the hundreds of tiny diodes.
HID lights come in metal halide (MH) or high pressure sodium (HPS). These lights emit the highest amount of lumens, but are also the least efficient and as such will release a lot of heat.
A standard 1000 Watt Metal halide bulb will emit around 115 000 lumens, and falls in the cooler, blue spectrum of around 3500-5000 K. High pressure sodium of the same power on the other hand offers even more lumens, and under 3500 K light. These lights are currently the main bulbs used for indoor and hydroponic growing. Their ideal light spectrums for each stage of plant growth, and high light intensity make them a great option for indoor growing. These bulbs tend to get hot during use however, and need to be vented or otherwise cooled using fans.
Choosing the Right Lighting
Choosing the right lighting for your indoor grow comes down to all of these factors. Choosing a light with the right color spectrum for whatever life stage your plants are in. And deciding the right intensity for the size of grow you have. Lumens are a good indication for HID and CFL lighting to indicate the power, but should not be relied upon as the sole indicator of the lights power and quality.
When looking for an indoor grow light, make sure you keep in mind the size of the grow, and the life stage your plants are in.