Cymbidium

Light is tricky to balance with the temperature requirements of the plants. Coming from higher elevations, cool temperatures, and somewhat exposed bright areas by streams in Asia, they need high light but cool temperatures. The maximum amount of light possible, short of burning, should be given to the plants, which would be about 32,250-64,500 lumens (3,000 to 6,000 foot-candles).

• In a greenhouse, 50% -100% full sun or about 32,250-64,500 lumens (3,000-6,000 foot-candles) with light shade at midday is ideal. Southern climates below the 37th parallel will need to use shade cloth. Northern growers can expose some species to full sun with no consequence.
• In the home (only miniatures are recommended), south, east, or west windows where they will get about 4+ hours of direct sun are ideal. You cannot sunburn a Cymbidium indoors.
• If using artificial lights, they should be on for 10 to 14 hours a day.

Temperature is critical for flowering standard and miniature Cymbidiums. While you can grow a Cymbidium at any reasonable temperature, hot or cool, Cymbidiums will only flower under cool to cold temperatures. Many growers in warmer climates, especially south of the 37th parallel get frustrated because they can grow a giant clump of Cymbidium foliage, but it never flowers. To flower well, a temperature difference between night 50F-57F (10C-14C) and day 75F (23.8C) is required starting in the fall and remaining there or cooler through winter and spring. The failsafe is to just keep the plants below 65F (18.3C) at all times in the fall, winter, and early spring. Cymbidiums will refuse to bloom if the temperature goes above 75F (23.8C) at any time. Miniature Cymbidiums can flower at temperatures several degrees warmer than this.

When plants are in bud, temperatures must be as constant as possible Cymbidiums can tolerate light frosts and survive, but this is not recommended. Bring them inside when temperatures dip to 40F (4.4C). In mild climates roughly below the 37th parallel, or in zone 8B and up, they can be grown outside year-round. A bright and cool location inside is best for winter months, such as an unheated enclosed sunporch.

A constant supply of moisture should be provided to cymbidiums, which are semi-terrestrial plants. They generally produce all their vegetative growth during the spring and summer and need the most water during that period. Water heavily during the growth season, keeping the potting material evenly and perpetually moist. Reduce water when the pseudobulbs complete growing in later summer allowing the mix to hit dryness, but then immediately watering. Keep barely moist during the winter, like a wrung-out sponge.

Keep humidity at 40% to 60% during the winter, especially if plants are in bud. Cymbidiums are tolerant of humidity swings during the summer if they are well-watered. Keep the air moving to prevent fungus (Botrytis) from spotting flowers. Cymbidiums that are grown outdoors in drier climates may need to be brought inside during the summer.

Fertilize at the proper time to help Cymbidiums flower. Use a high nitrogen fertilizer such as (30-10-10) from March until May, a balanced fertilizer such as (20-10-20 / 10-10-10) from June until September, and a blossom booster such as Dyna Grow Bloom (3-12-6) once you see spikes forming in early spring. Do not fertilize during the winter.

Heavy watering once every month is necessary to leach accumulated fertilizer salts from the potting medium. The best way to accomplish this is to water thoroughly on your normal watering day and then come back and water the plant again after an hour or so. This will allow time for the salts to dissolve and wash away.

Potting is usually done in the spring after flowering, usually every two years when potting medium decomposes. Shake the old potting mix off the roots. Dividing the plant can also be done at this time, if desired. Include at least one new growth and three pseudobulbs with a division. Pick a water-retentive potting mix; medium-grade fir bark with peat moss and perlite is a common mix. Although, compost or general potting soil for houseplants have been used successfully as well. Select a pot that will allow for at least two to three years of pseudobulb growth, 3-4 inches (8-10 cm) larger, before crowding the pot. Place the active growing pseudobulb(s) farthest from the side of the pot. Spread the roots over a cone-shaped mound of the mix in the bottom of the pot and fill the container with medium, working it among the roots and tamping firmly.

Individual back-bulbs can be left in the greenhouse environment bare-root until they show signs of a shoot. When they start to grow a new shoot, they should be potted up individually in regular medium. When in doubt, repot it like any normal houseplant, as Cymbidiums are terrestrial plants.

• Cymbidiums: Species and Hybrids
  Cymbidium Culture

Further information can be found on the Cymbidium genus page.

Best orchid care practices are also provided for watering, repotting, and fertilizer types. There are also detailed discussions of growing orchids indoors, outdoors, or in greenhouses.

For more information on genus name changes, see Taxonomy.