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Artificial Lighting for Orchids

Posted August 24th, 2016 by Ray Barkalow in , ,

orchids-in-terrariumFor those not lucky enough to have a greenhouse, or who have run out of space on window sills, the use of artificial light is a major “plus” to growing. You have a lot of options when it comes to choosing lighting, but you should do some thinking and planning before making a purchase. For example, some things to consider include:

  • Will this be a primary source of light for the plants, or a supplement to natural light?
  • Where will the fixture be located? In a living area or basement “grow room”?
  • Is heat generation a problem or a plus?
  • How large of an area will be lighted?
  • How much “head room” (distance from plants to the light) do you want?
  • What is your budget for lighting? (Don’t get cheap here – light is a crucial parameter in orchid growing.) Consider purchase price, bulb replacement, and operating costs.

There are Four Basic Types of Lighting AvailableOrchidSupplyWeb813

High Intensity Discharge (HID), fluorescent, incandescent, and light emitting diodes (LED) – each having its own pluses and minuses.

High Intensity Discharge (HID)

HID lighting is the most energy-efficient way to provide light in terms of light output per watt consumed. There are two types of HID lights commonly used – Metal Halide (MH) and High Pressure Sodium (HPS). Sometimes growers will use a combination of both. They are very bright, and do generate a great deal of heat, so they may not be the best choice for living areas of your home.

Metal Halide (MH) – 10,000 Hour Life

Metal halide bulbs produce light that favors the blue part of the spectrum, which is excellent for plant growth. If you are seeking a HID light for your primary light source, metal halide is the way to go, especially when you consider that newer technology has led to bulbs having boosted levels of the red end of the spectrum.

Watts Lumens per Watt Area Primary Light Source Areas Supplement

 

Operating Temperature (F)
250 125 3′ x 3′ 5′ x 5′ 400°-450°
400 125 5′ x 5′ 8′ x 8′ 450°-500°
1000 125 8′ x 8′ 12′ x 12′ 500°-550°
Working Height Purchase Price Bulb Costs Cost per Month (14 Hrs/Day @ $0.10/K WH)
24″-36″ $$$$ $$$ $10.50
36″-48″ $$$$$ $$$ $16.80
48″-60″ $$$$$$$ $$$$ $42.00

High Pressure Sodium (HPS) – 20,000 Hour Life

High pressure sodium bulbs emit light in the orange-red part of the spectrum, which can induce budding and flowering in plants. For that reason – and because they can lead to “leggy” growth – HPS bulbs are better suited as supplemental light sources, and are often used in greenhouses. The output spectrum tends to override the colors of flowers when viewed or photographed. They are more economical to use than MH, due to the greater light output and longer bulb life. They are often used in conjunction with metal halide bulbs.

Watts Lumens per Watt Area Primary Light Source Areas Supplement

 

Operating Temperature (F)
250 140 3′ x 3′ 5′ x 5′ 400°-450°
400 140 5′ x 5′ 8′ x 8′ 450°-500°
600 140 6′ x 6′ 10′ x 10′ 500°-550°
Working Height Purchase Price Bulb Costs Cost per Month (14 Hrs/Day @ $0.10/K WH)
24″-36″ $$$$ $$$ $10.50
36″-48″ $$$$$ $$$ $16.80
42″-54″ $$$$$$ $$$$ $25.20

Fluorescent – 20,000 Hour Life

For years, folks using fluorescent lighting have typically used inexpensive “shop lights” that utilized 4-, 40W MarilWebAdT12 bulbs. Those bulbs typically had output levels in the neighborhood of 35-40 lumens/watt, and usually had to be “right on top of” plants in order to provide adequate light levels. Fortunately, technology has advanced to the point of giving us highly efficient, long life compact fluorescents (CFL) and smaller diameter, more efficient T5 tubes. (Incidentally, the “T” number designation indicates the nominal diameter in 8ths of an inch – i.e., a T12 is 12/8ths or 1.5″ in diameter.) Because they generate so little heat, it is possible to place the lights quite close to plants without the fear of burning them. Like HPS and MH bulbs, one can find fluorescents that favor the red end of the usable spectrum (those with a “color temperature” of 2700°K to 3000°K) or blue end (greater than 7500°K), but those in the 5000°K to 6500°K range tend to be sufficiently “broad spectrum” to be a primary light source.

T5 fixtures are probably the best choice for lighting plants in a living area, and are excellent for isolated growing areas as well.

Type Size and Number Watts Lumens per Watt Area as Primary Light Source Area as Supplement
CFL 1 125 75 2′ x 2′ 3′ x 3′
CFL 1 200 75 3′ x 3′ 4′ x 4′
T12 1 40 40 1′ x 4′ 2′ x 5′
T5 1 x 2′ 24 90 1′ x 2′ 2′ x 3′
T5 4 x 2′ 96 90 2′ x 3′ 3′ x 4′
T5 1 x 4′ 54 90 1′ x 4′ 2′ x 5′
T5 4 x 4′ 216 90 2′ x 5′ 4′ x 6′
Operating Temperature (F) Working Height Purchase Price Bulb Cost Cost per Month (14 Hrs/Day @ $0.10/K WH)
125°-150° 3″ -18″ $ $ $1.68
125°-150° 6″-24″ $$ $$ $5.25
125°-150° 6″-24″ $$$ $$ $8.20
100°-125° 3″-24″ $ $ $1.68
100°-125° 3″-24″ $ $ $1.01
100°-125° 6″-24″ $$ $ $4.03
100°-125° 3″-24″ $$ $ $2.27
100°-125° 6″-36″ $$$ $ $9.07

Incandescent – 2,000 Hour Life

The old standard incandescent lamps may be the least expensive to purchase, but they are inefficient and produce a poor spectrum of light for plants. You’ll note that they are often tinted blue to shift the spectrum away from their strong red output. If you suddenly need to supplement the light on a single plant, you might get by with an incandescent grow light, but you’ll actually do much better with another choice.

Watts Lumens per Watt Area as Primary Light Source Area as Supplement Operating Temperature (F)
150 18 6″ x 6″ 12″ x 12″ 200°-250°
Working Height Purchase Price Bulb Cost Cost per Month (14 Hrs/Day @ $0.10/K WH)
12″-24″ $ $ $6.30

Light Emitting Diodes (LED) – 50,000+ Hour Life

LEDs are the latest in the evolution of horticultural lighting. They produce the least amount of heat and as the technology advances, it is possible to get 100 lumens per watt, or more from them. LED’s put out very specific wavelengths of light, so colors need to be mixed in order to approximate the desired spectrum.

For growing, it is common to use a combination of specific wavelengths of blue and red diodes, matching most closely the absorption peaks of chlorophyll. Unfortunately, with no green to reflect back to the eye, the plants take on a black, “alien” appearance. To overcome that, white chips are often added to make LEDs more applicable to living areas.

Ray Barkalow has been growing orchids for over 45 years, and owns First Rays, which offers horticultural products to the hobby grower.  He may be contacted at raybark@firstrays.com and you can visit his website at FirstRays.com.

Want More Information? Try These Articles:

5 Warning Signs that Your Orchids Could be in Trouble

How to Tell If You Are Over-Watering or Under-Watering your Orchids

Taming Wild Orchids

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