orchids - Knowledgebase Question

pasadena, ca
Question by camtwins3
August 9, 2007
How do I keep my orchids growing?

Answer from NGA
August 9, 2007


The ideal place in the home for growing orchids is a bright window, free from drafts, where your plants receive indirect sunlight both morning and afternoon. (A south window is best.) In winter, give orchids all the light possible. Light intensity should be between 1500 and 2000 foot candles the equivalent to a bright south-facing window. With extra large windows or especially intense sunlight, the light may be adjusted downward by moving plants 18 to 36 inches from the window. Plants in the home require a greater light intensity because they receive light from only one direction, while in a greenhouse they receive light from many sides.

Potted orchid plants may be set on decorative pebbles in a water-filled tray, saucer, or other container. Evaporation of water from pebbles provides humidity. Pebbles also make the growing area more attractive, while assuring good drainage. Mist your plants with distilled water because tap water can lead to salt deposits on the leaves. A plant which is kept soaking wet invites attack by bacteria and fungal diseases. If you are able to enclose an area like a greenhouse, you will find it easier to maintain a proper humidity.

Orchids are not as delicate and temperature sensitive plants as most people think. Most will adapt readily to conditions offered by any home or greenhouse. For growing purposes, we group orchids into three temperature classes:

The medium temperature class is represented by many Cattleyas, Epidendrums, Oncidiums, and Laelias, and most other commercially available orchids. The ideal minimum temperature is 60 degrees F nights and high 70s during the days. An occasional deviation will have no harmful effect. This group will do very well with the air, temperature, and light facilities found in the average home.

The cool class includes Cymbidiums, Cypripediums, Odontoglossums and Miltonias, and should be grown 5 degrees to 10 degrees F cooler than the medium class. These plants also require high light, so imagine cool, sunny October mornings as an example of the light and temperature that this class needs.

Warm class orchids are represented by Phalaenopsis, Paphiopedilums, Vandas, Rhynchostylus and Dendrohiums. These plants should be grown 5 degrees F warmer than those in the Medium Class. They do well in high humidity and can be grown outdoors in Georgia from late spring to early fall if shaded and protected from rain. Never expose orchids of this class to less than 45 degrees F.

Watering is the most important factor in orchid culture. A good rule of thumb is to water whenever the medium (osmunda fiber or bark mix) is dry. Orchids potted in bark require more frequent waterings than those in most other potting media, just as plants in clay pots require more frequent watering than those in plastic pots. Orchids may be grouped into three categories according to their moisture requirements.

Low Water Use. Cattleyas, Laeliocattleyas, Brassolaeliocattleyas, Oncidiums, Miltonias, and Odontoglossums are ephiphytes or "air rooted" orchids, with built-in "water tanks" or pseudobulbs. They should be allowed to dry out slightly between waterings so air can circulate between the epiphytic roots. Water every five days or so. In the heat of mid-summer, water may be needed every three or four days. During the short, cool days of winter, increase the time between waterings to 10 to 14 days. If you do err in watering, make sure it is on the dry side.

Moderate Water Use. Phalaenopsis, while also epiphytic are monopodial and do not have built-in tanks for water storage, but store some water in their leaves. They require watering similiar to ordinary house plants, but more frequent waterings than orchids with pseudobulbs. Water enough to keep the potting medium from becoming dry for more than a day or two.

High Water Use. Paphiopedilums and Haemeria orchids are semi-terrestrials or terrestrials (meaning "earth-rooted"). Unlike the preceding groups, they do not mind "wet feet." They like an abundance of moisture and the soil can remain damp for many days without any negative effects. Many terrestrial orchids are potted in peat based media which will naturally hold more water than the bark mixes.

Hope this information provides some guidance!

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