Incandescent? Florescent? Metal Halide? The Pros and Cons of Various Lighting Fixtures to Keep Your Indoor Orchids Flourishing

Image Courtesy of Hydro Gardens

There are several options when it comes to artificial light for orchids. Orchids need certain kinds of light in order to grow well and bloom. They also need enough of this light. Normal incandescent bulbs may look bright, but they are the least efficient source of lighting for plants. This is because they consume a lot of power and put out a lot of heat energy, but produce very little light that is useful for plants. Florescent light is far better in terms of the amount of usable light energy produced versus the amount of power used and the amount of heat produced. For most hobbyist and household orchid growers florescent light will be the most logical choice. One of the options for lighting is Metal Halide and High Pressure Sodium fixtures. These can be good choices for someone who has a lot of orchids, or a number of large orchids. MH and HPS fixtures put out a lot of light, but also produce a lot of heat. They can be very expensive and need to be housed in a specially designed casing with a ballast. They also tend to suck a lot of power and can be expensive to run.

Best Artificial Orchid Lighting Set-ups, Pros and Cons

Incandescent Bulbs: Normal incandescent bulbs you buy to light your house are essentially useless to orchids. You will need specialty broad spectrum bulbs. These bulbs have a spectrum of light that plants can use for photosynthesis. However, these lights are inefficient and will only be enough for one or two plants and will need to be so close that they may burn the plant, in order to do any good.

Florescent Fixtures: These are the most practical choice for most home growers. They are efficient, but still need to be used in an effective way. There are essentially two options. Compact florescent bulbs can be used by themselves in order to light a few plants. Otherwise, tubes can be used, but for most orchids two to four tubes will be necessary. Orchids that need greater light should be grown closer to (almost touching the tubes), those that need less can be grown farther away. Generally you will need to buy broad spectrum, or full spectrum bulbs, in order for them to be effective. These also will not work for tall orchids (because the light will not reach the lower parts of the plant), or very high light orchids, such as most Vandas. Florescent light can be highly economical and does not produce a lot of heat.

High Pressure Sodium Fixtures: These are the most effective lights for growing over a large area. They put out a lot of light, but also use a lot of energy. I have a 250 Watt HPS system and this allows me to grow orchids over approximately a five foot area. The fixture should generally be hung two to four feet above the plants. There are three drawbacks to these systems: They produce a lot of heat, they are expensive to run and the light they put out is in the red spectrum, so it does not look quite natural. This red light tends to encourage flowering, but can cause strange plant growth. They are also complicated to install and can be unsafe. The two most reputable companies that produce these fixtures are Sun System and Hydro Farm. If not properly installed these can be a fire hazard, so make sure yours is UL listed. They also tend to be at least $200 for a new system.

Metal Halide: These fixtures are a lot like the HPS ones, but the light appears more natural because it is further in the blue spectrum. This light also encourages healthier plant growth.

Here is a picture of my High Pressure Sodium Setup

The Top Myth Every Successful Orchid Grower Needs to Avoid

A little light never hurt an orchid, only a lot of light can.

Lack of light is one of the main reasons orchids won’t flower in the home. Don’t believe what they tell you about light in the basic guidelines for growing orchids. Many orchids benefit from filtered, or even direct morning and evening sun. Different types of orchids require different light levels. Vandopsis orchids can sometimes be grown in nearly full sun, as can some kinds of Cattleya. However, most orchids, even most Cattleya’s will burn from too much, or mid-day sun.

This is not caused by the light as you might think, but by the building up of heat within the leaf. Just like freezing, too much heat can actually break apart the cells, causing damage to the leaf and in extreme cases the entire plant.

Here is a list of suggested footcandle ranges for different orchids (see below for a definition of footcandles):

• Cattleya: 2,000-5,000 Footcandles
• Phalaenopsis: 1,000-2,000 Footcandles
• Oncidium: 1,000-3,000 Footcandles
• Dendrobium Phalaenopsis: High Light Levels
• Miltonias: 1,500-2,500 Footcandles
• Vandas: 4,000-5,000 Footcandles
• Paphiopedilums: 1,000-2,000 Footcandles

Several of these numbers were borrowed from the Orchids Limited website.

Generally, if the weather is not too hot then morning sun, or light during part of the day through an east, south, or west facing window can be very beneficial to orchids.

Light is necessary for orchids to flower. In fact, light is one of the main reasons orchids won’t flower in the home. They may be growing just fine, but that doesn’t mean they’re getting enough light to flower. Flowering takes a lot of energy and orchids get their energy from light and water. That orchid may look great in the middle of the room, but it will most likely never flower. This is true of most orchids, but not always true of Phalaenopsis and Paphiopedilums, as well as amazonica species and hybrids which can do well in normal household conditions in close proximity to a window. These orchids thrive in a range of light close to 1,000 lumens, which is what they’ll get next to an east or north facing window, or in a very bright room. However, they are especially low light orchids and cannot withstand direct sun on their leaves, with the exception of winter sunlight for a brief period in the far northern and southern latitudes.

Definition of Terms: Lumens, Footcandles

Light is generally measured in Lumens, or Footcandles. A footcandle is the amount of light produced in comparison to candles at one foot away. Therefore, two candles from one foot distance will emit two footcandles of light, a normal fluorescent light bulb will produce a couple thousand. One lumen is the amount of footcandles distributed over a one square foot area. In general an object will receive about 10,000 footcandles in full sun, on a bright sunny day in the middle of summer.

On the other hand, the middle of a room on a dull grey day, with only one incandescent light fixture will probably receive only a couple hundred lumens. Far too little for almost any orchid to grow and flower. Generally 1,000 footcandles can be achieved in a bright north or west facing window. As well as in the middle of a brightly lit room, on a bright day. For higher levels of light, an east or south facing window, or artificial light will be necessary. Be careful to guard orchids from hot midday or early afternoon sun, by using a sheer curtain (one that still lets light through). Lumens and Footcandles are best measured with a light meter (often used by photographers).

I will cover artificial lighting in a later posting. There are many options available to the light gardener, from High Pressure Sodium light fixtures to good old standard fluorescent lights.