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This is
an extraordinarily large and
diverse New World genus with
an equally diverse number of
habitats. Oncidiums may
originate anywhere from sea
level in the tropics to the
high elevations of the
Andes. This obviously makes
cultural generalizations
difficult. More specific
instructions may be
available from the grower.
Some genera included are
Aspasia, Brassia, warm-
growing miltonias (often
called the Brazilian type)
and many of their hybrids.
Light
needs can vary from bright
to nearly full direct sun
depending on the species.
Most will thrive with one to
several hours of sun a day.
Generally, thicker leaved
plants, such as "mule-ear"
and "equitant" oncidiums,
can stand more light. In a
greenhouse, 20 to 60 percent
shade is required, or about
2,000 to 6,000 foot-candles,
depending on the plants. In
the home, east, south or
west windows are ideal. Many
types of oncidiums will grow
under artificial light: Four
fluorescent tubes
supplemented with
incandescent bulbs and
placed 6 to 12 inches over
the plants are necessary for
proper growth. Metalhalide
and sodium-vapor bulbs also
provide sufficient light
without needing to be so
close to the plants.
Temperatures
for this group are generally
considered intermediate to
warm: 55 to 60 F at night,
and 80 to 85 F during the
day. Temperatures up to 95
to 100 F are tolerated if
humidity and air movement
are increased as the
temperatures rise, a good
general rule in any case.
Water
requirements vary with the
type of plant. Generally,
plants with large fleshy
roots or leaves need
less-frequent watering than
thin-leaved or thin-rooted
plants. Watering should be
thorough, and the medium
should dry at least halfway
through the pot before
watering again. This may be
every two to 10 days
depending on weather, pot
size and material, type of
orchid and type of potting
medium. Plants not actively
growing should be watered
less; many species have
winter rest periods.
Humidity
should be between 30 and 60
percent. Many oncidiums
require less humidity than
other orchids. Most
greenhouses have adequate
humidity. In the home,
placing the plants above
moist pebbles in trays is
ideal.
Fertilize
regularly while plants are
actively growing.
Applications of 30-10-10
formulations twice a month
are ideal for plants in a
bark-based potting medium. A
20-20-20 formulation should
be used on plants in other
media or on slabs. If skies
are cloudy, applications
once a month are sufficient.
Potting
should be done when new
growth is about one-half
mature, which is usually in
the spring. Fine-grade
potting media are usually
used with fine-rooted plants
and coarser mixes with
large-rooted plants; the
standard size is medium
grade. The plant should be
positioned in the pot so
that the newest growth is
farthest away from the edge
of the pot, allowing the
maximum number of new
growths before crowding the
pot. Spread the roots over a
cone of potting medium and
fill in around the roots.
Firm the medium around the
roots. Keep humidity high
and the potting medium dry
until new roots form.
Equitant and mule-ear
oncidiums, as well as other
fleshy-leaved or
large-rooted plants, can be
grown on slabs of cork bark
or tree fern or in pots
filled with a coarse,
well-drained medium such as
charcoal. This allows the
drying between waterings
that these types need.
Oncidium culture was prepared by:
American Orchid Society, 6000 S. Olive Ave., West Palm Beach, FL 33405
Cattleya
Care
Phalaenopsis
Care
Basic
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