Orchids - Knowledgebase Question

Greer, SC
Avatar for merianne1548
Question by merianne1548
May 19, 2007
I pride myself with my green thumb God has blessed me with. I have tried several times to grow Orchids but for some reason I can't seem to keep them from dying. Any advice would be greatly appreciated. Thank you Merianne Allen

Answer from NGA
May 19, 2007
I'm glad you have a green thumb! Gardening is a rewarding hobby, and a frustrating one if you find that you can grow everything except what you most want to grow; orchids!

Here are some basics to help you succeed with your next orchids:

Growing Medium
There are many different types of orchid potting medium used in orchid culture. The overall consideration is to provide structural support for the orchid roots, but also to provide lots of air spaces between medium particles. Many orchid plants are grown in osmunda fiber. This fiber comes from the roots of the Osmunda fern that is native to Australia and the Pacific. The tough, wiry fibers break down very slowly and is an ideal potting medium. Fresh pine bark is also a popular medium but is usually mixed with other amendments before use. Both materials are sometimes mixed with peat and perlite or vermiculite. Some orchids are even grown in pebbles mixed with bark. Most orchid roots are adapted to being exposed to air and harsh conditions, but cannot tolerate being wet for more than a day or two.

Orchids grow slowly compared to houseplants. However, most orchids need to be repotted about once every two years. To pot an orchid, the pot is filled about two-thirds with orchid potting medium, then the plant is set in the pot with its roots spread out. The growing tip either centered (monopodials) or placed two fingers from the pot rim (sympodial). Then additional media is packed tightly around the plant to hold it in place. You should be able to turn the pot upside down without the orchid or medium falling out. Practice will insure successful repotting. When the plant outgrows the pot by extending the new shoots over the edge, usually about every two years, it is time to repot.

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.

Many orchids can be grown in a greenhouse or outdoors. All will require partial shade. Therefore, it is best to shade the section of the greenhouse you intend using or else grow them in an area that you have already shaded for foliage plants or African violets. Dendrobium Oncidium and Vanda will grow best in 20-30% of normal outdoor light, whereas Phalaenopsis-type orchids require only 10- 15 % of normal light.

Artificial Light
If you have neither a greenhouse nor the proper windowsill conditions, fluorescent lighting provides good results. You can grow and flower many types of orchids in the darkest basement or shadiest apartment with the addition of just one shop light. Most orchid hobbyists find having at least four 36" or 48" fluorescent tubes provides excellent light levels. Each group of orchids (primarily those with low to medium light requirements) will need a minimum of two forty-watt fluorescent light tubes hung six inches above the plants.

Keep lights on for a minimum of 12 hours per day in order to provide the minimal amount of light necessary for proper growth and flowering. If you are able to place your fluorescent light setup near a sunny window, your orchid flowering chances will increase. The best type of fluorescent tubes seem to be those designed specifically for plants.

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.

During cold, freezing night temperatures, all orchid plants should be moved away from the window to provide a protective airspace against freezing. Air temperature can be 15 to 20 degrees F cooler near the windows than the room temperature.

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. If you grow the plants in pots suspended in the air, they will dry out more rapidly than bench grown plants and will need watering more frequently. 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.

Outdoor Conditions. Cymhidiums and many other orchids, such as cattleyas, can be grown outdoors during frost-free months in Georgia. They also like an abundance of moisture - but with good drainage and plentiful root aeration. However, do not plant tropical/greenhouse orchids outdoors in your garden soil. The soils are too dense to allow the roots to survive.

For best results, fertilize orchids with soluble plant food. When fertilizing plants growing in osmunda, bark or peat/bark mixes, use a complete liquid fertilizer with a 20-20-20 analysis, or a 30-10-10 orchid-special fertilizer. Don't fertilize more than once a month. Apply the fertilizer in place of a normal water application. It is always best to use fertilizer at 1/2 the recommended rate. Orchids are adapted to environments where nutritional levels of the soil or bark are very low. More orchids are killed because of over-fertilization and over-watering than by any other cause.

In greenhouses, a small fan should be run continuously to circulate the air. A window left ajar in all but the coldest of weather may also be adequate to provide proper ventilation indoors. Air conditioning may harm orchids because the air is much too cold coming out of the unit. Keep orchid plants out of cold drafts and away from heating vents.

Hope this information is helpful!

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