Light is one of the most important elements in growing orchids. Even with the correct temperature, right level of water, appropriate amount of fertilizer, your orchids will not bloom without sufficient illumination. If your orchid doesn’t give you any flowers for a long time (keep in mind that most orchids bloom only once a year), instead of begging, scolding or threatening your orchid, your first trouble-shooting task is to find out if your orchid has enough of this critical element.
To make light levels easier to understand, growers categorize them as low, medium and high. You might hear that a Phalaenopsis orchid requires low light, whereas a Vanda orchid likes high light. But what do they really mean?
If there is a way to measure the hotness of a chili pepper (the unit is called Scoville Heat Unit), there must be a way to measure the intensity of light. Yes, you are right; “foot-candle” is used to measure illumination. Basically a foot-candle (fc) is the amount of light a one-foot radius sphere would receive from a candle in the center. In the full summer sun, you might find as much as 10,000 fc of light, but the indoor light next to a window might be as low as 100 fc.
Back to orchid growing. Here are what the three light groups mean.
|Light Group||Foot-Candles||Sample Orchid Genus for Light Group|
|Low||1,200 to 2,000 fc||Phalaenopsis (moth orchid), Paphiopedilum (slipper orchid)|
|Medium||2,000 to 3,000 fc||Miltonia, Cattleya (corsage orchid)|
|High||3000+ fc||Vanda, Brassavola|
You can buy one of those fancy light meters to see how much light your growing area receives, but orchid growing does not need such precision. It’s sufficient to gauge the light level without sacrificing your shoe money.
You can do a “hand-over-leaves test.” Just put your hand six inches above the leaves of your orchid plant in the light. If you see a sharp shadow casting on the plant, then you have pretty strong/high light. A soft shadow means there is medium light and almost no shadow means low light, which is probably too little for orchid growing. Keep in mind that the intensity of natural light varies throughout the day, so you might want to do this test at various times of the day.
You can also tell by looking at the color of leaves. A lush, dark green might look good and healthy to you, but it is your orchid’s way of telling you that it is not receiving enough light. The leaves might also be elongated as they are trying to reach out for the light. On the other hand, if you give too much light to your plant (for example, grow it outdoors in full sun), your orchid can get burned. Your orchid might have a red tinge if it reaches the maximum light level it can take.
While light intensity is important, the duration is also crucial. Give your orchids six to ten hours of light at the desired intensity. But if you don’t have a place where your orchid receives enough light, you can supplement natural light with artificial light. Heck, you can even grow your orchids completely under artificial lights. Be sure to visit my page Indoor Orchid Growing to find out more.