Growing Under Lights

We are all familiar with the idea that “Plants require light to grow”, however this is not strictly true. Plants utilize energy in the form of radiation for their necessary processes, solar radiation is the primary source of this energy.

The main photosynthetic of plants is chlorophyll. Chlorophyll mainly absorbs light in the red and blue spectrums.

Visible Light Spectrum


What we perceive as ‘light’ is not necessarily what plants require for healthy growth, this is why simply using a normal light bulb is very ineffective.

There are many different lights specifically designed for providing the required light for plants

High Intensity Discharge (HID) Lights

High Intensity Light (HID)HID lights are very efficient. HID lights are always used with a reflector and require a ballast to operate. Check the manufacturers installation instructions to ensure that you have sufficient space around the light, HID lights can produce a considerable amount of heat.

There are two types of HID lights:

High Pressure Sodium Lights (HPS)

HPS lights produce light in the orange to red spectrum, this light can trigger an increase of budding and flowering in plants. HPS are a great supplementary light used with natural sunlight of Metal Halide lights. Bulbs will last up to 10,000 hours operation.

Metal Halide Lights (MH)

MH lights produce light in the blue spectrum, this color light promotes plant growth and is great for leafy green growth and keeping the plants compact (without blue spectrum light the plants will grow thin and lanky). Bulbs will last up to 18,000 hours operation.


Fluorescent Grow Lights

Sun Blaze LightFluorescent lights have been used for a long time to encourage growth of plants in fish tanks. Until fairly recently fluorescent lights have not been powerful enough and have been too large and bulky to be used commercially.

There are now compact bulbs and much higher power tubes.

Fluorescent lights are very energy efficient and can have a very wide and varied spectrum of light output, the also produce a lot less heat than HID lights.

Compact Fluorescent LightLights should be placed within a few feet of the plants if possible.

Check that you get the correct light spectrum (red for flowering, blue for plant growth) or purchase full spectrum bulbs.

It is not necessary to use reflectors with fluorescent lights, use reflectors when you need to direct the light to a specific location.

Incandescent Grow Lights

Incandescent Grow LightThese are the cheapest lights to buy and are the most inefficient and are the worst light source for plants.

It would be much more cost effective and you would get a much better light source using a compact fluorescent grow light.


LED Grow Lights

LED lights have progressed massively over the last few years and they are now becoming popular in all sorts of technology, this is because they are cheap and very efficient.

There are some drawbacks of using LED grow lights, the main one is that the light can give thLemnis Lightinge plants a very unnatural appearance, the level of light can also be lower than other types of light.

LED lights give of almost no heat so can be place virtually anywhere you want.

The latest LED system I discovered has been developed by Lemnis Lighting. As you can see there are lights in the red and blue spectrum’s to specifically target the requirements of the plants. The missing yellow and green spectrum colors cause the plants to appear unnatural.


General Lighting Guidelines

  • Blue light spectrum for plant growth
  • Red light spectrum for flowering and budding
  • Use light reflectors to direct the light
  • Paint and solid walls white to reflect white
  • Watch out for heat from the lights
  • Light your plants for 14-16 hours for foliage growth
  • Light your plants for 12-16 hours when flowering
  • Make sure you plants have darkness of at least 8 hours


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