Orchids Need Light to Bloom
Not Enough Light
Too Dark: This Dendrobium was grown without enought light. Note the dark green color of the leaves, the thin, spindly central cane, and the way the leaves cannot hold themselves upright.
Next to over-watering, insufficient light falling on their orchids causes new growers the most grief, and light requirement is often the most overlooked factor when considering an orchid plant’s needs. If their plants are beginning to fail, most people new to orchids will change the amount and frequency of their watering, fertilizing, heating–just about everything else–before they attempt to change their light levels, and that’s no surprise: most homes, especially older ones, aren’t the brightest-lit things in the world and most people already grow their indoor plants around the brightest windows they’ve got. Light levels feel about as permanent and unchangeable as mothers-in-law: you pretty much have to take what you get.
If your orchid is blooming and you’d like to use it to brighten a darker space in your home, by all means, do so. A week or two in an area too dim to grow in won’t hurt your plant at all. But a week or two is it! Don’t leave your plant there! An orchid left to grow beside that droopy potted palm in the darkest corner of the house will begin to show signs of illness: thin, dark green, new growth, sagging leaves, even brownish-black crown rot if water was allowed to stand in the “hollow” where your plant’s new leaves are sprouting from. Remember, to thrive, orchids commonly found for sale need light and moving air. (There are actually some subterranean orchid species that need almost complete darkness, but we won’t go into those here…)
But how much light is enough? How much is too much? How do you know how much you’ve actually got?
Too Much Light: Though not quite to the point of burn, this plant was not given proper shade. Paphiopedilums are terrestrials and too much light will yellow their leaves, as shown here.
To grow well, most orchids need at least as much light during the growing season as is found under the shade of a large tree in direct sun, with absolutely no direct sun hitting your orchid plant. To bloom well and heavily, Cattleyas and Vandas need as much light as is found out in the open on a cloudy, gloomy day. If that’s too broad a definition, light level requirements for each of the major orchid genera expressed in footcandles can be found under the appropriate link of the main “CARE” page. (1 footcandle is the amount of light received by a surface lit by one candle one foot away.)
Too much light is usually the culprit when orchid leaves turn a bright, whitish yellow, (or black and burnt if exposed to direct sun) but for beginners, too much light is hardly ever the problem.
So how much light do you have coming in through that window? Since the perception of brightness is a subjective matter that varies with age–even gender–from person to person, the only way to really tell is to measure it, using a light meter. Meters that display brightness levels in footcandles, lux, and lumens can be bought at specialty stores, but meters like these are usually expensive, especially if you’re just trying out your first orchid and don’t want to invest a whole lot of money right at the beginning. If you have an older, manual camera with a built-in light meter, you can use that to measure your light levels. Here’s how:
Set the camera’s film speed to ASA 200 and its shutter speed to 1/125 of a second. Aim the camera at a white sheet of paper placed where your orchid is growing. Get close enough so that the meter records only the light reflected from the paper: the paper must fill the viewfinder. Focus on the paper and adjust the lens aperture until a correct exposure shows on the camera’s light meter. Once the exposure is correct, look down at the aperture setting on the lens. The F-stop reading will convert approximately into footcandles as follows:
F-stop Footcandles
2.8 32
4.0 64
5.6 125
8.0 250
11 500
16 1,000
22 2,000
The vast majority of orchids grown commercially for sale require between 800 and 3000 footcandles of light to thrive and bloom. Specifics for the major genera can be found on the main “CARE” page. Compare these requirements to the 50,000 footcandles received by a plant in full sun, and you’ll realize why orchids burn in direct sunlight. Compare the requirements to the 30 – 80 footcandles found in the typical living room, and it’s easy to see why most beginning orchid growers don’t give their plants enough light. If your orchid is receiving the amount of light it needs, bravo! That’s one hurdle you’ve already overcome! If your growing area is too dim, you can supplement your natural light with artificial. Fluorescent fixtures and bulbs can be bought very inexpensively at any major home maintenance outlet, and your orchids will reward you with year after year of blooms and lush growth for some time a little bit of money well spent.
So don’t forget about the light!