When growing plants indoors (hydroponically) one of the most important components is the lighting system and set-up. The most important part of lighting is the light bulb. Eye Hortilux, Sunmaster,  and Solarmax are some bulb manufacturers that offer many different light bulb options for the indoor, hydroponic gardener.

There are different types of  light bulbs to consider to use in the growing process. When considering which type of light bulb to use, the main features to look for are spectrum and output. The serious grower can get even more out of their crop by fine tuning the spectrum to the stage of plant growth, and/or spin the lights.

Light Bulb Spectrum

Full-spectrum is best. Of course the sun is full spectrum, and plants have evolved for many millions of years to adapt to sunlight.

Below, the chart on the left is what the human eye sees; on the right, what the plant prefers:

The Lumen rating of a bulb is not a good measurement for plant growth, because it is based on what the human eye can see. A full spectrum light is like music, with bass, treble, and everything in between.

High Output Bulbs

The best full-spectrum lights for digital ballasts are Pulse Start Metal Halide (PMSH). The best full-spectrum lights for magnetic ballasts are Ceramic Metal Halide (CMH). That is because in addition to being a true full spectrum, they are also high output.

Here is the Spectral Chart:

Chart for 4k CMH

High Pressure Sodium Bulbs

HPS is high output, but not full spectrum; it is mostly yellow-orange. Premium hps like Hortilux are super, that is, higher output than standard hps; but don’t last as long as standard output. HPS works well only at high levels of intensity, so it takes more watts to get the job done. HPS uses a ceramic arc tube which is glued together and leaks with heat stress

Distribution of Light onto Leaf Surfaces

While it is true that a 1000 watt light is the highest output, a single point of light would concentrate the light too much in one small spot, instead of evenly distributing over a larger area. Right below the heat zone around a bulb, is the zone of too-high intensity. This can best be measured with a light meter. Probably the optimum level of intensity is 4300 foot candles; 5500 foot candles would be the maximum and not all varieties want 5500 fc under all environmental conditions.

Light Spectrum for Different Stages

Different portions of the spectrum perform different functions. Blue light has the highest energy level, reduces stem elongation, increases rooting, and induces growth hormones. Red light has the greatest ability to bounce and penetrate the leaf canopy, increases growth of leafs and buds, and induces blooming hormones.

The plant cannot overdose on plant hormones; excessive amounts are simply stored. That is why you can use a full spectrum light for all stages. However, by enhancing relevant portions of the spectrum depending on the stage, you can increase efficiency of plant growth.

This post  barely skims the surface of all the information out there on different types of bulbs. There is even more information on how to use different bubls to their full potential. Remember when looking for a bulb that wattage, type of bulb (MH, HPS, CMH), different light spectrum, all make a difference in different ways. Get the most of your lighting system by choosing the right bulb!

Similar Posts:

• Fresh Tips (Grow Lights #8 – Enhanced Conversion Bulbs)
• Fluorescent grow lights
• Grow Lights #9 – Full Spectrum “Dual Arc Tube” Bulbs
• Grow Lights – Getting Started with indoor plant lighting
• Fresh Tips (Grow Lights #4 – HID Grow Lights)

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