Seasonal Light
If cold temperatures are confining your gardening to indoors, your orchids can still keep you busy. In addition to the autumn chores I wrote about recently, this is a good time of year to look at light conditions. Orchids that originate from the tropics do not experience very short days or weak sun in their natural habitats. The sun remains strong in the tropics all year. Farther from the equator, the sun weakens considerably in fall and winter. To compensate, growers in temperature climates can gradually move their orchids into brighter light. Cattleyas, Dendrobiums, Epidendrums, and Oncidiums can be slowly acclimated to full sun. Even shade lovers, like Phals, Paphs, and Masdevallias, can tolerate a little direct sun. No matter the variety, increase light gradually to prevent sunburn. It usually takes me 2 weeks of gradual adjustments to move them into the brightest locale. Pay special attention to maintaining high humidity with the extra light.
If the sun isn’t cooperative, you may want to add artificial lights to boost light levels for the dormant season. Fluorescent lights work well since they last a long time, use little electricity, and don’t get very hot. Light bulbs should be close to the leaves, just 6-8 inches (15-20 cm) away, but not so close that leaves can burn. Just like natural light, any increases with artificial light need to be done gradually. Burns can cause large dead spots on leaves, usually starting white and then turning black. If leaves turn reddish at the edges, then the orchid is receiving its maximum light exposure. That’s good because it’s a guarantee the orchid is getting enough light to bloom, but stay vigilant to prevent burns.
Remember that most orchids need enough light to keep their leaves a light green color. Dark green leaves may mean insufficient light, while yellow leaves may mean too much light. Most importantly, when spring arrives don’t forget to move orchids back into the shade.
Explore posts in the same categories: Dormancy, Growing
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November 1st, 2009 at 8:28 am
None of my orchis ever flowered until I added lights in wintertime. We live north in Canada and sunlight is very weak in winter. I use growlights for 15 hours a day and the orchids stay vigorous in winter.
November 6th, 2009 at 4:13 pm
this is really helpful info. it totally makes sense to supplement light in the winter, but i never thought about it before. blooming orchids, here i come!
November 9th, 2009 at 9:26 pm
Just live in the tropics, and then it won’t be a problem!
November 12th, 2009 at 4:03 pm
The sun is too weak in winter to really burn any leaves, so I doubt its a problem to move orchids into brighter light.
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