Growing Orchids
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Paul A. Thomas, Extension Horticulturist-Floriculture
Orchids belong to the most diverse family of plants known to man. There are over
880 genera, 28,000 species and well over 300,000 registered cultivars currently
documented. These numbers only begin to tell the true story behind the
evolutionary success of modern day orchids. Orchids are the most rapidly
(genetically) changing group of plants on earth and more new species have been
discovered over the last few thousand years than any other plant group known.
Orchids are also one of the most adaptable plant groups on earth. Some
Australian orchids grow entirely underground, and many tropical jungle orchids
grow in the upper branches of trees. Tundra, rainforest, mountain, grassy plain,
desert and swamp environments contain numerous orchid species.
Orchids produce seed pods with literally hundreds of thousands of seed that are
released and scattered by the wind. Orchid seeds must establish a symbiotic
relationship with a special fungus to survive its first year of life. The fungi
gathers water and minerals for itself and the seedling, and the seedling shares
its sugars from photosynthesis with the fungus. Only one or two orchid seeds
will ever germinate and survive on that perfect crevice or depression that is
both moist and has the fungus present. Even then, its chances to survive in the
wild long enough to bloom are slim.
To avoid this problem, greenhouse growers sow orchid seeds on moist, sugar-rich,
sterile agar, or they cut out growing clumps of orchid cells and place them on
the agar. These techniques allow many hundreds of orchid plants to survive to
maturity. New and improved hybrids can be mass produced rapidly. This is
important as orchids are very slow growing. Many orchids take five to seven
years to mature to flowering. You can see why breeding three or four orchid
generations could span a person's lifetime just to get one new hybrid propagated
sufficiently for sale.
Classification
All orchids belong to the Orchid Family, Orchidaceae (or-Kid-ACE-ee-ee). Orchids
are divided into two basic growth types: monopodial and sympodial. Monopodial
orchids have a central stem which grows continuously from the tip. Flowers are
produced from the stem between the leaves, usually alternately from side to
side. Phalaenopsis orchids are a good example. Sympodial orchids, such as
cattleyas, laelias and paphiopedilums, possess a rhizome which sends out a
shoot. This develops into a stem and leaves and eventually produces flowers. In
time, from the base of this growth, a new shoot develops and so on in a
continuous cycle. The buds are often, though not always, protected by a sheath.
The mid section of stems of sympodial orchids are often expanded into
water-storage organs called pseudobulbs. These vary greatly in size and shape,
ranging from tall and pencil-thin to bulbous and onion-like. The leaves vary
too, some being soft and folded like a fan, others thick and leathery. The roots
of epiphytic orchids have an outer layer or corky cells called velamen, which
protects the thin, living cortex within. These adaptations allow orchids to
absorb water and nutrients rapidly from raindrops, but protect roots, stems and
leaves from water loss during dry periods. Most orchids are adapted to conserve
water and should be cared for as such.
Orchid Cultural Requirements
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.
Light
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.
Humidity
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.
Temperature
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
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.
LLow 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.
Fertilization
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.
Ventilation
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. Airconditioning 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.
Orchid Pests and Diseases
Orchids have few insect pests or diseases if properly cared for. It is important
to have a problem identified before attempting control. Take a sample to your
county Extension agent and follow recommended treatments suggested. Many disease
prevention tips are provided in an orchid disease guide published by the
American Orchid Society. Wiping leaves with a warm, soapy, wet cloth is
sufficient to eradicate insects like mealy bugs if you have but a few plants in
the house. Be careful because many insecticides can damage your orchids. Read
the label to see if the pesticide can be safely used on orchids specifically. If
you have questions, ask your county Extension agent.
Orchids for Hobby Growers
One of the most frequently asked Questions from the hobby grower is, "What type
or variety of orchid should I grow?" Usually when you mention the word "orchid"
most people immediately think of the purple-flowered Cattleyas, and rightly so
as they have long been the most popular in the trade. However, the genus
Cattleya contains a mere 50 species of the 28,000 known. Many, many other
orchids do wonderfully in the home.
Hobby growers should try growing hybrids of Phalaenopsis, Paphiopedilum,
Dendrobium, Oncidium, Vanda and Epidendrum. Phalaenopsis orchids are excellent
for beginners. They may produce up to 15 or more flowers per spike. The flowers
measure up to four inches across. Flowers may remain open for six weeks or
longer. Frequently when a spike is cut, a secondary spike will develop on the
old stalk below the original flower head, thus extending the blooming season.
Phalaenopsis plants are very easy to grow.
Dendrobium hybrids are some of the better corsage type orchids. Lavender or
white flowers are borne in profusion on a well-grown plant and are long lasting.
They are a prolific group in that offset plantlets are frequently produced on
the cane. When each offiet has produced several aerial roots, it can be cut from
the parent plant and will frequently flower after one year of growth.
Oncidiums, commonly, referred to as dancing girls, are also easy to grow. These
dainty yellow and brown or white and brown flowers are suitable if used alone or
in combination with other orchids. Large flowered Oncidium sdhacelatum - with
their yellow and brown color combination can be made into a corsage. These hardy
plants flower well even under adverse growing conditions.
Vandas are becoming popular among orchid growers. The wide range of colors which
includes some fairly good blues and browns and long lived flowers has added
greatly to their popularity. Vandas may grow to be very large plants, sometimes
10 to 12 feet high, but they grow very slowly. A plant two feet tall may be
seven or eight years old. Vandas are often grown outdoors in hanging baskets
during the summer months.
A tough group of orchids is the Epidendrums. Epidendrum hybrids are becoming
popular plants.
These are undoubtedly one of the easiest orchids to grow and one of the most
prolific groups. The tall, thin, reed-like growths constantly put forth new
plantlets. It is relatively simple to take tip cuttings having a few aerial
roots. Although the flowers are small, about one inch in size, they are produced
in great profusion.
Paphiopedilums are one of the best orchid groups to grow under artificial
lighting. There are many spectacular hybrids available, and quite a number of
species. They are not fragrant, but have very interesting and colorful "lady
slipper" shaped flowers. Due to import regulations and conservation
considerations, we recommend you grow only orchid hybrids so as not to promote
the collecting of species from the wild.
For more information on orchid plant care and disease control, contact the
American Orchid Society, Membership Services Department, 6000 South Olive Ave,
West Palm Beach, Fl. 33405-9974.
Fact Sheet H-93-013
The University of Georgia and Ft. Valley State College, the U.S. Department of
Agriculture and counties of the state cooperating. The Cooperative Extension
Service offers educational programs, assistance and materials to all people
without regard to race, color, national origin, age, sex or disability.
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