Where there’s a will, there’s a way. You can still grow orchids under artificial plant light even if natural sunlight is insufficient or unavailable. Orchids grown indoors under good artificial light can be just as healthy as the ones grown in natural light. However, it is not as easy as putting your orchids close to a light bulb. Having a basic understanding of plant lights and your orchids’ light requirements will greatly enhance your success.
One great thing about growing orchids under plant lights is that the light intensity does not need to be as high. The reason is that artificial plant light is very uniform. No matter how rainy or cloudy outside, or how short the winter day, your plant light is available as soon as you (or your timer) turn it on. Moreover, reflectors and reflecting surfaces make the available light more efficient, as well as allow the light to reach the underside of the leaves. Furthermore, you can expose your orchids to longer hours of light to compensate for the lesser intensity. Generally speaking, you can provide 10% to 20% less light to your orchids when grown under plant lights. Check out my Orchid Light page to understand the light intensity requirements of different orchids.
The farther away from the light source, the less intense the light is. Also, for standard fluorescent light, the middle of the tube emits more intense light than the ends. So try to put your plants in the middle if possible.
Some growers like to imitate nature and turn their artificial plant lights on when the sun rises and off when the sun sets. But others like to extend the day light to accelerate growth. My recommendation is to have your lights on for 14 to 16 hours in the summer and 12 to 14 hours in the winter. I don’t recommend providing more than 16 hours of light because darkness is as important as light to your orchids’ health. Some orchids are day-length sensitive as it is a signal for them to determine the time to bloom. For example, the famous Cattleya labiata sets buds in the fall when the day length shortens. Oncidium and Miltonia are also sensitive to day lengths. So for those orchids, you should gradually decrease the duration of light in the fall and winter.
You might have learned in elementary school that the green pigment in leaves, Chlorophyll, absorbs light to produce food for plant growth. Chlorophyll absorbs the blue and red wavelengths of light and reflects the green (hence the green color). Therefore, even though natural sunlight contains many colors, only the blue and red are used by plants. Blue light, sometimes referred as “cool” light, is primarily responsible for leaf growth while red light, sometimes referred as “warm” light, promotes flowering and fruiting. The good proportion is to have about one part of red light to three parts of blue light. This is important knowledge to have when you choose the right artificial plant lights for your orchids because different light sources emit different colors.
Types of Artificial Plant Lights
Manufacturers seem to be coming up with new types of artificial lights every other month, but don’t let that confuse or intimidate you. Essentially, I like to think that there are four common types of artificial lights for plants. They are:
- Incandescent light
- Fluorescent light
- Metal halide light
- High-pressure sodium light
The basic incandescent lights are the most typical and inexpensive light bulbs you find in hardware stores. They emit mostly red light, so should be used only with fluorescent lights to provide a fuller spectrum light. One huge disadvantage is that incandescent light bulbs generate tremendous amount of heat, so don’t put your orchids within 2 feet (60 centimeters) of the light bulb or the leaves will burn. Incandescent light bulbs also deteriorate quickly and need to be replaced in 3 to 5 months. And because a lot of energy is converted into heat, the light is not very intense.
Some newer “growth” incandescent lights are engineered to provide more blue/red spectrum balanced light, so they are good for providing supplement lights to your orchids. However, they are still insufficient to be used alone.
Fluorescent lights come in many different varieties, and the more advanced versions are engineered to provide the full spectrum of light. They are also way more efficient at turning energy into light. They are cool to touch, hence are unlikely to burn your orchids. Even though a fluorescent light bulb’s life span is 25 times longer than an incandescent bulb, fluorescent lights should be replaced every 18 to 24 months, because they will deteriorate and become less intense over time.
To grow less light-demanding orchids, like Phalaenopsis, 4 tubes of 60 watt standard fluorescent light placed no further than 4 inches (10 centimeters) away will be sufficient. Remember that the light is most intense in the middle of the tube, so sure to place them close to the center. Once your Phalaenopsis sends out a spike, remove it from the light so that the spike doesn’t touch the tube.
High output fluorescent light is another option. It can emit twice as much light as the standard cool white fluorescent light. Hence you can grow orchids that require medium light, such as Miltonia and Cattleya, if you use eight 24-watt tubes of high output fluorescent lights with reflectors. However, high output fluorescent light requires a special fixture, so the initial investment can be substantial.
If space is an issue, you can use compact fluorescent lights. They are fluorescent lights twisted into a bulb shape so that they can be fitted into a regular incandescent light fixture. Compact fluorescent lights are just like regular fluorescent lights; they emit little heat and come in red/warm, blue/cool or full spectrum versions.
For your light-loving orchids like Vanda, florescent light is probably not enough, as there are just so many tubes you can fit into one place. Moreover, long plants doesn’t allow the light to be placed close enough to all parts of the plant. For these situations, you might want to consider more powerful lights, like the metal halide or high-pressure sodium lights described below.
Metal halide light is a high-intensity discharge light (HID) that can render light similar to natural sunlight. Orchids grown under metal halide light will be compact (as opposed to “leggy” and long), just like a healthy plant that receives sufficient natural sunlight. Typically metal halide light comes in 400 and 1000 Watt, which can be used to light a 25 square feet (2.3 square meter) and 144 square feet (13.3 square meter) room respectively. Just put the higher light demanding plants closer to the lamp. If you have a rectangle or irregular shaped growing area, you can also install a light mover. It systematically moves your metal halide light with a railing system, so that your orchids placed in the peripheral area can enjoy as much light as the ones placed in the center.
Such superior light quality does come with a price. Compared to fluorescent light, metal halide lights and the special fixtures are not cheap. Moreover, it is recommended that you change the light bulb once a year, so the price adds up.
High-pressure sodium light is another high-intensity discharge light (HID). It lasts longer than metal halide light (2 years vs. 1 year) and it emits even stronger light. However, high-pressure sodium light gives out a red/warm light, which makes your plant look sick and pale. Moreover, orchids grown solely under high pressure sodium light become tall and leggy, like they are trying to reach out for more light. However, the red/warm light does promote flowering in orchids, so it is desirable to use high-pressure sodium light in conjunction with metal halide light. In fact, many fixtures are designed to hold a metal halide bulb and a high pressure sodium bulb.
Here is a table to do a quick and dirty comparison for the different lights for your orchids:
|Incandescent||Fluorescent||Metal Halide||High-Pressure Sodium|
|Light color||Red/Warm||Both Red/Warm and Blue/Cool are available||Both Red/Warm and Blue/Cool are available||Red/Warm|
|Heat Emission||Very high heat||Low heat output||Medium low heat output||High heat output|
|Bulb Lifespan||750 hours||10,000 to 20,000 hours||10,000 to 20,000 hours||24,000 hours|
|Replace Bulb After||3 to 5 months||8 to 24 months||<250 Watt: 6 months>400 Watt: 1 year||All: 2 yearsSon/Agro: 1 year|
|Light Intensity||Low||Low to medium||Very High||Extremely High|
|Lumens per Watt (1 lumen in 1 foot = 1 foot-candle)||Up to 20 lumen||45 to 90 lumen||80 to 125 lumen||100 to 150 lumen|
|Typical Bulb Wattage||15 to 150 Watt||20 and 100 Watt||50 to 1000 Watt||35 to 1000 Watt|
|Cost of bulbs||$||$$$||$$$$$||$$$$$|
|Cost of fixture||$||$ (compact) to $$$$ (high-output)||$$$$$||$$$$$|