Orchid: Cymbidium

cymbidiumCymbidium orchids are native to tropical Asia and Australia. They are best known for their incredibly thick petals that are hard and waxy. The blossom size and number of flowers vary by variety, ranging from an inch to five inches in diameter, and from a few flowers to more than 20 per flowering stem. They come in all colors except blue and true red. In their native habitat, they are epiphytes, or they grow in trees without soil supporting their roots. All cymbidiums have short, bulbous pseudobulbs, or thickened stems, which store water and bear multiple, strap-like, arching leaves.

Cymbidium orchids perform best in very high light and must receive strong light to produce healthy growth and flower well. They need a potting mix that drains well and made up of redwood bark chips, coarse charcoal or perlite, supplemented with unmilled sphagnum moss or coarse peat moss to enhance water retention.

They need typical household temperatures; 65 to 70 degrees Fahrenheit during the day and 58 to 60 degrees at night. In addition, standard cymbidiums, or the large-flowered varieties, require a six to eight week cool period in the fall when night temperatures are at least 45 to 50 degrees Fahrenheit, or even down to freezing, to form buds. Modern miniature hybrids do not require such low temperatures to induce flower buds; a low temperature of 60 degrees is adequate.Cymbidium

These plants thrive in 50 to 80 percent relative humidity. To increase humidity, run a room humidifier or place the pot on a tray filled with pebbles and water. Keep the water level in the tray below the bottom of the pot to prevent water wicking into the pot which, over time, may lead to root rot.

Fertilize these orchids frequently when new growth is forming, generally from spring through summer, with a water-soluble commercial orchid fertilizer. A 30-10-10 formulation may be used for orchids grown in pure bark and a 20-20-20 formulation for those in all other mixes.

Yellow and red orchid

Cymbidiums bloom only once a year and the season of bloom varies by species or hybrid. Repot these orchids every two to three years when new growth begins, generally in spring.

Mealybugs and scale insects are occasionally attracted to cymbidiums. They are also susceptible to viral infections and root rot.

For "Viruses in Plants" refer to message number 1443.

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For more information, see the following Colorado State University Extension fact sheet(s).

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Updated Thursday, March 17, 2016